Archive for the ‘antioxidants’ Category

Oxaliplatin-Induced Neuropathy: Oxidative Stress as Pathological Mechanism. Protective Effect of Silibinin

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Posted 16 Mar 2012 — by James Street
Category alpha tocopherol, antioxidants, Silibinin

Deparment of Preclinical and Clinical Pharmacology, University of Florence, Florence, Italy

Received 30 August 2011; received in revised form 22 November 2011; accepted 28 November 2011. published online 13 February 2012.

Abstract

Oxaliplatin is the standard treatment for advanced colorectal cancer. Its dose-limiting toxicity is the development of a painful neuropathic syndrome sustained by unclear mechanisms. Although the oxidative hypothesis is a matter of debate, direct data about oxidative damage induced in vivo by anticancer agents are lacking and the efficacy of the available antioxidant compounds are unsatisfactory. In a rat model of painful oxaliplatin-induced neuropathy (2.4 mgkg−1 i.p., daily for 21 days), we described an important component of oxidative stress. In the plasma of oxaliplatin-treated rats, the increases in carbonylated protein and thiobarbituric acid reactive substances were the index of the resultant protein oxidation and lipoperoxidation, respectively. The same pattern of oxidation was revealed also in the sciatic nerve, and in the spinal cord where the damage reached the DNA level. The antioxidant compound silibinin (100 mgkg−1 per os), administered once a day, starting from the first day of oxaliplatin injection until the 20th, prevented oxidative damage as did α-tocopherol. Repetitive administration of silibinin, as well as α-tocopherol, reduced oxaliplatin-dependent pain induced by mechanical and thermal stimuli. Antioxidants were also able to improve motor coordination. The antineuropathic effect of both molecules improved by about 50% oxaliplatin-induced behavioral alterations.

Perspective

This study characterizes oxidative stress parameters in a rat model of oxaliplatin-induced neuropathy. A relationship between the improvement of oxidative alterations and pain relief is established in rats treated with natural antioxidant compounds like α-tocopherol and silibinin. Silibinin could be a valid therapeutic option for chemotherapy-induced neuropathy.

Key words: Neuropathic pain, α-tocopherol, disease modifying agent, lipoperoxidation, carbonylated protein

High Doses of Antioxidants Including Vitamin C Do Not Decrease the Efficacy of Chemotherapy by Abram Hoffer, M.D., Ph.D.

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Posted 21 Jun 2011 — by James Street
Category antioxidants, Chemotherapy, Vitamin C

(For a 2008 update on this important topic: http://www.doctoryourself.com/chemovitC.html )

Reprinted with permission of the author and the Townsend Letter for Doctors and Patients, 911 Tyler Street, Pt. Townsend WA 98368;             (360) 385-6021 begin_of_the_skype_highlighting (360) 385-6021 end_of_the_skype_highlighting

The idea that the use of antioxidants decreases the efficacy of chemotherapy is being used more and more by orthodox oncologists. It is based upon their hypothesis that anything which decreases the oxidant effect of drugs will decrease the efficacy of chemotherapy. More and more I hear this from my patients after they are diagnosed and chemotherapy is discussed with them by their oncologists. This opinion is not universal, but my guess is that about 75% of oncologists hold this view.

Their view is that chemotherapy destroys tumor tissue because it introduces powerful oxidation products, free radicals, and that anything which decreases that must interfere with treatment. They know they are using sub-lethal amounts of toxic compounds which would never pass FDA standards in any different context. The aim is to kill all the tumor tissue without killing all the other tissues in the body. This is always a close call. Therefore, since vitamin C is a good antioxidant it must not be given with chemotherapy. One of my patients was told by his oncologist that if he took vitamin C he would not be given any chemotherapy.

Well, what are the facts? The first fact is that there are no clinical series which show that patients given vitamin C and chemotherapy fare worse than those not given this vitamin. On the contrary, all the published series show just the opposite. I have treated over 1,100 cases with large doses of vitamin C and most of them had chemotherapy.(1-4) I have examined the follow up data and find that the mean difference on prolongation of life was heavily in favor of the use of the vitamins. In the first series I published with Linus Pauling those patients on my program lived 10 to 20 times as long as the patients not receiving the vitamin.

Recently Kedar N. Prasad et al. (5) after reviewing 71 scientific papers, found no evidence that antioxidants did interfere with the therapeutic effect of chemotherapy and, on the contrary, suggest the hypothesis that it would increase the efficacy. He is properly cautious, but anyone reading his paper knows that it is clear the probability that these antioxidants prevent the therapeutic activity of chemotherapy is very low, and the probability that they do the opposite, i.e enhance the action of these toxic drugs, is relatively high. Prasad et al. (6) concluded, “Antioxidants such as retinoids, vitamin E, vitamin C and carotenoids inhibit the growth of cancer cells. These antioxidants individually, and in combination, enhance the effects of x-irradiation, chemotherapeutic agents, and certain biological response modifiers such as hyperthermia, sodium butyrate and interferon, on cancer cells. Antioxidants individually protect normal cells against some of the toxicities produced by these therapeutic agents. Therefore, the fear of oncologists and radiation therapists that these antioxidants may protect cancer cells against free radicals that are generated by these agents is unfounded. It should be pointed out that other antioxidants such as sulfhydryl compounds will protect cancer cells at least against radiation damage. This is not true for any of the proposed antioxidant vitamins and carotenoids.”

Even earlier Charles B. Simone et al. (7) on the basis of a large number of clinical studies (he also examined 71 scientific papers) came to the same conclusion. He reported, “In a recent study of 50 patients with early-stage breast cancer I evaluated the treatment side effects of radiation alone, or radiation combined with chemotherapy, while the patients took therapeutic doses of nutrients. Patients also followed the Simone Ten Point Plan. Patients were asked to evaluate their own response to the treatment in terms of its impact on their quality of life. The results of the study were impressive: “More than 90% of both groups noted improvement in their physical symptoms, cognitive ability, performance, sexual function, general well-being and life satisfaction. Not one subject in either group reported a worsening of symptoms.” He concluded, “…cancer patients should modify their lifestyles using the Ten Point Plan, which included modifying nutritional factors and taking certain vitamins and minerals especially if they are receiving chemotherapy, and/or radiation.” (my emphasis)

Labriola et al. (8) concluded that vitamin C may prevent the therapeutic effect of chemotherapy if given concurrently and recommended that antioxidants be withheld until after the chemotherapy is completed. It is not clear whether they meant that the antioxidants should be withheld throughout the entire series of chemotherapy sessions or that it should be withheld only for the day that chemotherapy is being given. If the latter is his suggestion, there is no harm done to the patients. Most of them cannot take anything, including vitamins, during these sessions. He based his conclusion on one case which suggested this had happened and upon a hypothetical examination of the role of free radicals and antioxidants on the action of chemotherapy on cancer cells.

His report elicited two rebuttals, Reilly (9) and Gignac. (10) I will not repeat the arguments, but it was evident that Dr. Labriola was not convinced by the points put forward by Reilly and Gignac. I think the factoid repeated by Dr. Labriola would have a much better chance of becoming a fact if he had considered the following points:

ONE:  What is the therapeutic value of chemotherapy without any antioxidants? Even within the field of standard oncology there is a debate whether chemotherapy has any merit except for a small number of cancers (Moss). (11) Before one can claim that a treatment has been inhibited, surely there must be pretty good evidence that the treatment has any merit to begin with. It is possible (we do not know the probability for this) that chemotherapy interferes with the therapeutic value of the antioxidants. Almost all the studies testing large doses of vitamin C yielded positive results while there is no such unanimity with respect to chemotherapy.

TWO: The difference between possibility and probability. Most people do not distinguish between these two. Theoretically anything is possible, and it is certainly possible that taking vitamin C might prevent the toxic “beneficial” effect of chemotherapy. In the same way when one buys a lottery ticket, it is possible they may win. People confuse these two terms, which is why lotteries are so popular. The real statistic is the probability. What is the probability that patients receiving vitamin C during their chemotherapy will not fare as well? The lottery ticket may give one a probability of winning of one in a million, and the possibility that vitamin C may prevent the therapeutic effect of chemotherapy may be equally low. We can only assume from the literature reviewed by Simone, by Prasad, by Lamson and Brignall, and more recently by Moss (12) that the real probability must be extremely low. As I have pointed out earlier, I have seen no evidence that adding vitamin C inhibited the therapeutic effect of chemotherapy. Just the opposite. Patients on my orthomolecular program live substantially longer and about 40% achieved over four year cure rates.(13)

THREE: If he had not tried to bolster his argument by referring so frequently to the peer-reviewed journal in which his paper appeared. This is certainly no guarantee of fact. The first factoid that vitamin C caused kidney stones appeared in eminently peer-reviewed journals. All the factoids regarding vitamins appeared first in peer-reviewed journals. You may recall Linus Pauling’s joke that peers are people who pee together. I can assure you that articles attacking the use of vitamins have very ready access to peer-reviewed journals, but they would not have accepted their report had they tried to conclude from one patient that vitamin C taken during chemotherapy was therapeutic. This would not even be sent to the peer review committee because they do not accept anecdotes – unless of course they become scientific when they contain something adverse against vitamins.

FOUR: Moss points out that oncologists have no objection to using xenobiotic antioxidants during chemotherapy. This includes Amifostine which decreases the toxicity of radiation but is too toxic on its own and is not used; Mesna, a drug used around the world to protect against the toxic side effects of ifosfamide which damages the urinary system; and Cardiozane, which counters Adriamycin’s toxicity. There are over 500 papers showing the safety of the latter drug. In one clinical trial using a drug similar to Adriamycin, one-quarter of the patients suffered damage to their hearts. When given Cardiozane concurrently only 7% did. Thus it appears that only orthomolecular or natural antioxidants are potentially dangerous. Synthetic antioxidants protect against the toxic effect of drugs but do not increase their therapeutic value. In sharp contrast, natural antioxidants not only protect against the toxic effect of drugs but also increase their efficacy in destroying cancer cells.

FIVE: Dr. Labriola emphasizes that long term studies must be used. I agree, and for this reason I followed up my patients since 1977. In my series, hardly any patients receiving chemotherapy but not antioxidants survived very long. But chemotherapy is used by many oncologists who know it will not extend life, because there is nothing else that they can do and they feel they have to do something.

A. Hoffer MD PhD

References
1. Hoffer A & Pauling L: Hardin Jones biostatistical analysis of mortality data for cohorts of cancer patients with a large fraction surviving at the termination of the study and a comparison of survival times of cancer patients receiving large regular oral doses of vitamin C and other nutrients with similar patients not receiving those doses. J Orthomolecular Medicine 5:143-154, 1990. Reprinted in, Cancer and Vitamin C, E Cameron and L Pauling, Camino Books, Inc. P.O. Box 59026, Phil. PA, 19102, 1993.

2. Hoffer A & Pauling L: Hardin Jones biostatistical analysis of mortality data for a second set of cohorts of cancer patients with a large fraction surviving at the termination of the study and a comparison of survival times of cancer patients receiving large regular oral doses of vitamin C and other nutrients with similar patients not receiving these doses. J of Orthomolecular Medicine, 8:1547-167, 1993.

3. Hoffer A: Orthomolecular Oncology. In, Adjuvant Nutrition in Cancer Treatment, Eds. P Quillin & RM Williams. 1992 Symposium Proceedings, Sponsored by Cancer Treatment Research Foundation and American College of Nutrition. Cancer Treatment Research Foundation, 3455 Salt Creek Lane, Suite 200, Arlington Heights, IL 60005-1090, 331-362, 1994.

4. Hoffer A. One Patient’s Recovery From Lymphoma. Townsend Letter for Doctors and Patients #160:50-51, 1996.

5. Prasad KN, Kumar A, Kochupillai V & Cole WC. High Doses of Multiple Antioxidant Vitamins: Essential Ingredients in Improving the Efficacy of Standard Cancer Therapy. Journal American College of Nutrition 18:13-25, 1999.

6. Prasad KN, Cole WC & Prasad JE. Multiple Antioxidant Vitamins as an Adjunct to Standard and Experimental Cancer Therapies. Z.Onkol/J. of Oncol 31:1201-1078, 1999.

7. Simone CB, Simone NL & Simone CB. Nutrients and Cancer Treatment. International Journal of Integrative Medicine 1:20-24, 1999.

8. Labriola D & Livingston R. Possible Interactions Between Dietary Antioxidants and Chemotherapy. Oncology 13:1003-1008, 1999, and Editorial to Townsend Letter for Doctors and Patients, November 1999.

9. Reilly P. Dr. Labriola’s Editorial on Antioxidants and Chemotherapy, Townsend Letter for Doctors and Patients Feb/Mar 2000, 90-91.

10. Gignac MA. Antioxidants and Chemotherapy. What You Need to Know Before Following Dr. Labriola’s Advice. Townsend Letter for Doctors and Patients Feb/March 2000, 88-89.

11. Moss RW. Questioning Chemotherapy. Equinox Press, Brooklyn, New York.

12. Moss RW. Antioxidants Against Cancer. Equinox Presss Inc. Brooklyn, New York, 1999.

13. Hoffer A. Vitamin C and Cancer. Quarry Press, Kingston, ON 2000.

Chemotherapy Doesn’t Work, So Blame Vitamin C

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Posted 21 Jun 2011 — by James Street
Category Antioxidants, antioxidants, antioxidents, Chemotherapy, Vitamin C



FOR IMMEDIATE RELEASE
Orthomolecular Medicine News Service, October 7, 2008

(OMNS, October 7, 2008) When Memorial Sloan-Kettering Cancer Center announces that vitamin C may interfere with chemotherapy, the news media trumpet it far and wide. But before cancer patients throw away their vitamin C supplements, they need to know rest of the story.

Most of the media dutifully reported the researchers’ claim that the equivalent of 2,000 mg of vitamin C “blunted the effectiveness of the chemotherapy drugs.” But only some of the media included a study author’s incredible statement that “If you take an oral dose even as low as 100 milligrams a day” even “that could be harmful” during chemotherapy (1)

100 mg “could be harmful”? That’s the amount of vitamin C in a few glasses of orange juice. Something is very wrong here.

First of all, this research involved mice with implanted cancerous tumors; it was not a trial on cancer patients. A mouse study is a long way from a human clinical trial. This obvious difference was conceded by the study authors. However, there is a more subtle, and probably much more important factor they did not consider: all mice make their own vitamin C. Indeed, mice make quite a lot. Adjusted for body weight, mice synthesize the human body weight equivalent of approximately 10,000 milligrams of vitamin C each day. (2) Incredibly, sick mice make even more. Mice given transplanted tumors become sick mice.

Secondly, previous research has demonstrated that mice with cancer respond well to high-dose vitamin C therapy. One study found, “With an increase in the amount of ascorbic acid there is a highly significant decrease in the first-order rate constant for appearance of the first spontaneous mammary tumor. . . Striking differences were observed between the 0.076% ascorbic acid and the control groups, which synthesize the vitamin.” (3) Another study concluded that: “A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of malignant lesions was observed with high statistical significance. By 20 weeks, approximately five times as many mice had developed serious lesions in the zero-ascorbate as in the high-ascorbate group.” (4) Interestingly enough, when this research was first publicized, the media discounted these findings saying that mouse studies were not particularly applicable to people.

Thirdly, a mouse’s ability to make vitamin C, and a great deal of it, is an overlooked confounding factor that may well render the entire experiment invalid. If the Sloan-Kettering team had tried their experiment on Guinea pigs, their results might have been very different. Guinea pigs are more like human beings in that they cannot make their own vitamin C. As controls for comparison, the researchers also treated “no-added-vitamin C” mouse cancers with chemotherapy. Chemo worked just fine on those mice, by the researchers own admission. And each of those mice was internally synthesizing a body weight equivalent of 10,000 mg/day of vitamin C, even though given none supplementally.

So how come 10,000 mg of vitamin C does not interfere with chemo treatment, and 2,000 mg – or even 100 mg – supposedly does?

A sweeping recommendation warning cancer patients to not take supplemental vitamin C, not even 100 mg, is irresponsible. It is impossible to justify caution about taking 100 mg of vitamin C daily when your animal subjects made the equivalent of one hundred times that amount, and chemotherapy in them was still reported as effective. You cannot have it both ways. If a synthesized 10,000 mg of C does not interfere, there can be no real “interference” or “blunting” from a supplemental 2,000 mg. And most certainly not from 100 mg.

The study did report tumor shrinkage, in both groups of mice receiving chemo. That is not surprising. Chemotherapy’s claimed success is based on tumor shrinkage. But tumor shrinkage, encouraging though it is, is not a reliable indicator of long-term cancer survival. As cancer research critic Philip Day puts it, many patients are “cured but dead” after five years, hardly a long-term survival. Day, noting that this is not because oncologists are not trying, explains the chemotherapy quandary: “You can be insincere, or you can be sincerely wrong.” (5)

The Sloan-Kettering study team seems to have missed the essential point that vitamin C is not just an antioxidant. Inside cancer tumors, it also acts as a prooxidant, killing malignant cells. Comments Dr. Steve Hickey, of Manchester, UK: “Essentially, the paper seems to be rather misguided and shows a lack of understanding of the dual nature of vitamin C in tumors. Chemotherapy has been shown by over 40 years of clinical trials not to work in the majority of tumors, and its use is counterproductive.”

Chemotherapy drugs have come and gone; the five year survival rate for cancer treated with chemo has remained virtually unchanged for decades. Unfortunately, just over 2% of all cancers respond to chemotherapy. Specifically, one scientific review concluded, “The overall contribution of curative and adjuvant cytotoxic chemotherapy to 5-year survival in adults was estimated to be 2.3% in Australia and 2.1% in the USA . . . chemotherapy only makes a minor contribution to cancer survival. To justify the continued funding and availability of drugs used in cytotoxic chemotherapy, a rigorous evaluation of the cost-effectiveness and impact on quality of life is urgently required.” (6)

Perhaps this new, very well-publicized study results from an ever-growing realization that chemotherapy is largely ineffective, and the search is on for the reason why. Vitamin C should not be made the scapegoat.

Vitamin C, in doses well over 100 mg/day, is known to help prevent cancer. (7) Nearly 30 years ago, a review concluded that “Many factors involved in host resistance to neoplasia are significantly dependent upon the availability of ascorbate.” (8) Beginning in the 1970s, many well-designed studies show that very large doses of vitamin C improve both quality and length of life for cancer patients since they invariably are “significantly depleted of ascorbic acid.” When given intravenous vitamin C, “The mean survival time is more than 4.2 times as great for the ascorbate subjects . . . This simple and safe form of medication is of definite value in the treatment of patients with advanced cancer.” (9) Additional clinical trials have confirmed this over the past several decades. (10)

Even more importantly, recent research indicates that in high doses, vitamin C is selectively toxic to cancer cells. That means vitamin C can function very much like chemotherapy is supposed to, but without the severe side effects of chemotherapy. “A regimen of daily pharmacologic ascorbate treatment significantly decreased growth rates of ovarian, pancreatic, and glioblastoma tumors established in mice. Similar pharmacologic concentrations were readily achieved in humans given ascorbate intravenously.” (11)

“Cautioning” the public to avoid taking any supplemental amount of vitamin C will decrease host resistance to cancer, increase the incidence of this dreaded disease, and shorten survival times. A cynic might say it will also create a larger market for chemotherapy.

Is vitamin C a commercial competitor for chemo? To answer this, one needs to consider what appears to be serious conflict of interest at Sloan-Kettering. Bristol-Myers-Squibb makes chemotherapeutic drugs. According to a DEF 14A SEC filing of March 22, 2006, the Chairman of the Board of Bristol-Myers-Squibb is also a director of the Coca-Cola Company, and Honorary Chairman of Memorial Sloan-Kettering Cancer Center. (http://sec.edgar-online.com/2006/03/22/0001193125-06-060566/Section8.asp). A previous Bristol-Myers-Squibb Chairman of the Board was a director of the New York Times Company. He was also Vice Chairman of the Board of Overseers and the Board of Managers of Memorial Sloan-Kettering Cancer Center and Chairman of the Board of Managers of Sloan-Kettering Institute for Cancer Research. (http://www.secinfo.com/dsvrt.bC7.htm) Some sources say that there are even more Bristol-Myers-Squibb directors who have or held positions on the board at Memorial Sloan-Kettering Cancer Center. (12)

Positive endorsements for vitamin C as a cancer fighter are not in the interests of any pharmaceutical company. Scaring the public away from vitamin C might be profitable. It appears that Sloan-Kettering is biased. So are media reports that attack vitamins.

If the Sloan-Kettering study authors’ recommendations to not take 2,000 mg, or even 100 mg, of vitamin C are followed, there will definitely be an increase in the number of people that need chemotherapy.

References:

(1) Doheny K. Vitamin C and chemotherapy: bad combo? Supplementing with vitamin C may reduce effectiveness of chemotherapy drugs, study shows. WebMD Health News. http://www.webmd.com/cancer/news/20081001/vitamin-c-chemotherapy-bad-combo

(2) Chatterjee IB, Majumder AK, Nandi BK, Subramanian N. Synthesis and some major functions of vitamin C in animals. Ann N Y Acad Sci. 1975 Sep 30;258:24-47.

(3) Pauling L, Nixon JC, Stitt F et al. Effect of dietary ascorbic acid on the incidence of spontaneous mammary tumors in RIII mice. Proc Natl Acad Sci U S A. 1985 Aug;82(15):5185-9.

(4) Pauling L. Effect of ascorbic acid on incidence of spontaneous mammary tumors and UV-light-induced skin tumors in mice. Am J Clin Nutr. 1991 Dec;54(6 Suppl):1252S-1255S. Read the full paper free of charge at http://www.ajcn.org/cgi/reprint/54/6/1252S

(5) Day P. in the documentary film Food Matters, http://www.foodmatters.tv See also: Day P. Cancer: why we’re still dying to know the truth. Credence Publications, 1999. ISBN-10: 0953501248; SBN-13: 978-0953501243

(6) Morgan G, Ward R, Barton M. The contribution of cytotoxic chemotherapy to 5-year survival in adult malignancies. Clin Oncol (R Coll Radiol). 2004 Dec;16(8):549-60.

(7) Enstrom JE, Kanim LE, Klein MA. Vitamin C intake and mortality among a sample of the United States population. Epidemiology. 1992 May;3(3):194-202.

(8) Cameron E, Pauling L, Leibovitz B. Ascorbic acid and cancer: a review. Cancer Res. 1979 Mar;39(3):663-81.

(9) Cameron E, Pauling L. Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A. 1976 Oct;73(10):3685-9. Read the original paper at http://profiles.nlm.nih.gov/MM/B/B/K/Z/_/mmbbkz.pdf

(10) Murata A, Morishige F, and Yamaguchi H. Prolongation of survival times of terminal cancer patients by administration of large doses of ascorbate. International Journal of Vitamin and Nutrition Research Suppl., 23, 1982. p. 103-113. And: Null G, Robins H, Tanenbaum, M, and Jennings P. Vitamin C and the treatment of cancer: abstracts and commentary from the scientific literature. The Townsend Letter for Doctors and Patients, 1997. April/May. And: Vitamin C and cancer revisited. Proc Natl Acad Sci U S A. 2008 Aug 12;105(32):11037-8. Also: Riordan HD, Riordan NH, Jackson JA et al. Intravenous vitamin C as a chemotherapy agent: a report on clinical cases. Puerto Rico Health Sciences J, June 2004, 23(2): 115-118.

(11) Chen Q, Espey MG, Sun AY et al. Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A. 2008 Aug 12;105(32):11105-9. See also: Chen Q, Espey MG, Sun AY et al. Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo. Proc Natl Acad Sci U S A. 2007 May 22;104(21):8749-54. And: Chen Q, Espey MG, Krishna MC et al. Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. Proc Natl Acad Sci U S A. 2005 Sep 20;102(38):13604-9. And: Padayatty et al. Intravenously administered vitamin C as cancer therapy: three cases. Canadian Medical Association Journal, 2006. 174(7), March 28, p 937-942. http://www.cmaj.ca/cgi/reprint/174/7/937. Also: Riordan NH et al. Intravenous ascorbate as a tumor cytotoxic chemotherapeutic agent. Medical Hypotheses, 1995. 44(3). p 207-213, March.

(12) Moss R. Questioning Chemotherapy. Equinox Press, 1995. ISBN-10: 188102525X; ISBN-13: 978-1881025252. See also: The Cancer Industry. Equinox Press, 1996. ISBN-10: 1881025098; ISBN-13: 978-1881025092.

For more information:

Cameron E. and Pauling L. Cancer and vitamin C, revised edition. Philadelphia: Camino Books, 1993.

Hickey S and Roberts H. Cancer: nutrition and survival. Lulu Press, 2005. ISBN: 141166339X.

Hoffer A. Healing cancer: complementary vitamin and drug treatments. Ontario: CCNM Press, 2004. ISBN-10: 1897025114; ISBN-13: 978-1897025116.

For free access to an online archive of peer-reviewed, full-text nutrition therapy papers: http://www.orthomed.org/jom/jomlist.htm or http://orthomolecular.org/library/jom

Nutritional Medicine is Orthomolecular Medicine

Orthomolecular medicine uses safe, effective nutritional therapy to fight illness. For more information: http://www.orthomolecular.org

The peer-reviewed Orthomolecular Medicine News Service is a non-profit and non-commercial informational resource.

Editorial Review Board:

Damien Downing, M.D.
Harold D. Foster, Ph.D.
Steve Hickey, Ph.D.
Abram Hoffer, M.D., Ph.D.
James A. Jackson, PhD
Bo H. Jonsson, MD, Ph.D
Thomas Levy, M.D., J.D.
Erik Paterson, M.D.
Gert E. Shuitemaker, Ph.D.

Andrew W. Saul, Ph.D., Editor and contact person. Email: omns@orthomolecular.org

MITIGATION OF CHEMOTHERAPY SIDE EFFECTS

Life Extension
Cancer Chemotherapy

Cancer cells are everything we would like healthy cells to be: They quickly adapt to toxic environments, they readily alter themselves to assure their continued survival, and they utilize biologic mechanisms to promote cellular immortality. All of these factors make cancer an extremely difficult disease to treat.

Chemotherapy drugs have a high rate of failure because they usually kill only specific types of cancer cells within a tumor or the cancer cells mutate and become resistant to the chemotherapy. Cancer chemotherapy could save more lives if the latest scientific findings were incorporated into clinical medicine.

What concerns us is that respected cancer journals are publishing articles that identify safer and more effective treatment regimens, yet few oncologists are incorporating these synergistic methods into their clinical practice. Cancer patients often suffer through chemotherapy sessions that do not integrate the latest scientific findings. Our objective is to provide the patient with more options to discuss with their oncologist and to bring about multimodality approaches to improve the probability of a successful outcome.

It is impossible to design a single chemotherapy protocol that is effective against all types of cancer. The oncologist might need to administer several chemotherapy drugs at varying doses because tumor cells express survival factors with a wide degree of individual cell variability. This protocol conveys the findings from published scientific studies so that a cancer patient will have a logical basis to augment the effects of chemotherapy and also reduce the potential for side effects.

How Does Chemotherapy Work?
According to the National Cancer Institute, almost all normal cells grow and die in a controlled way through a process called apoptosis. Cancer cells, on the other hand, keep dividing and forming more cells without a control mechanism to induce normal apoptosis.

Anticancer drugs destroy cancer cells by stopping them from growing or dividing at one or more points in their growth cycle. Chemotherapy may consist of one or several cytotoxic drugs that kill cells by one or more mechanisms. The chemotherapy regimen chosen by most conventional oncologists is based on the type of cancer being treated. As you will read later in this protocol, there are factors other than the type of cancer that can be used to determine the ideal chemotherapy drugs that should be used to treat an individual patient.

The goal of chemotherapy is to shrink primary tumors, slow the tumor growth, and kill cancer cells that may have spread (metastasized) to other parts of the body from the original, primary tumor. However, chemotherapy kills both cancer cells and healthy normal cells. Oncologists try to minimize damage to normal cells and to enhance the cell killing (cytotoxic) effect on cancer cells. Too often, unfortunately, this delicate balance is not achieved.

Clinical studies show that for certain types of cancer chemotherapy prolongs survival and increases the percentage of patients achieving a remission. A partial remission is defined as 50% or greater reduction in the measurable parameters of tumor growth as may be found on physical examination, radiologic study, or by biomarker levels from a blood or urine test. A complete remission is defined as complete disappearance of all such manifestations of disease. The goal of all oncologists is to strive for a complete remission that lasts a long time–a durable complete remission, or CR. Unfortunately, the vast majority of remissions that are achieved are partial remissions. Too often, these are measured in weeks to months and not in years. Some types of cancer do not show any meaningful response to chemotherapy.


CHOOSING THE BEST CHEMOTHERAPY DRUGS TO KILL YOUR TUMOR

It is highly desirable to know what drugs are effective against your particular cancer cells before these toxic agents are systemically administered to your body. A company called Rational Therapeutics, Inc., performs chemosensitivity tests on living specimens of your cancer cells to determine the optimal combination of chemotherapy drugs.

Dr. Robert Nagourney, a prominent hematologist/oncologist, founded Rational Therapeutics, Inc., in 1993. Rational Therapeutics pioneers cancer therapies that are specifically tailored for each individual patient. They are a leader in individualized cancer strategies. With no economic ties to outside healthcare organizations, recommendations are made without financial or scientific prejudice.

Rational Therapeutics develops and provides cancer therapy recommendations that have been designed scientifically for each patient. Following the collection of living cancer cells obtained at the time of biopsy or surgery, Rational Therapeutics performs an Ex-Vivo Apoptotic (EVA) assay on your tumor sample to measure drug activity (sensitivity and resistance). This will determine exactly which drug(s) will be most effective for you. They then make a treatment recommendation. The treatment program developed through this approach is known as assay-directed therapy.

At present, medical oncologists, according to fixed schedules, prescribe chemotherapy. These schedules are standardized drug regimens that correspond to specific cancers by type or diagnosis. These schedules, developed over many years of clinical trials, assign patients to the drugs for which they have the greatest statistical probability of response.

Patients with cancers that exhibit multidrug resistance will likely receive treatments that are wrong for them. A failed attempt at chemotherapy is detrimental to the physical and emotional well being of patients, is financially burdensome, and may preclude further effective therapies.

Rational Therapeutics’ EVA assay uses your living tumor cells to determine which drug or drug combination induces apoptosis in the laboratory. Each patient is highly individualized with regard to sensitivity to chemotherapy drugs. A patient’s responsiveness to chemotherapy is as unique as their fingerprints.

Rational Therapeutics, leading the way in custom-tailored, assay-directed therapy, provides personal cancer strategies based on the tumor response in the laboratory. This eliminates much of the guesswork prior to the patient undergoing the potentially toxic side effects of chemotherapy regimens that could prove to be of little value against their cancer. Rational Therapeutics may be contacted at:

Rational Therapeutics, Inc.
750 East 29th Street
Long Beach, CA 90806
Telephone:             (562) 989-6455 begin_of_the_skype_highlighting (562) 989-6455 end_of_the_skype_highlighting ; Fax: (562) 989-8160
Web site: www.rationaltherapeutics.com

In addition to the EVA chemosensitivity testing, we advocate immunohistochemistry testing of your tumor to provide additional data that will assist in making treatment decisions. The importance of the immunohistochemistry test is described in the Cancer Treatment: The Critical Factors protocol. The immunohistochemistry test can be done if your physician sends a specimen of your tumor to a specialty laboratory called Impath (www.impath.com). Impath can be reached by calling             (800) 447-5816 begin_of_the_skype_highlighting (800) 447-5816 end_of_the_skype_highlighting . Impath also performs chemosensitivity testing of living tumors (fresh specimens). Because many chemotherapy patients’ primary tumors were previously removed or irradiated, Impath can perform the immunohistochemistry test with a frozen or parraffin-preserved tissue sample that is accessible through the pathology laboratory that examined your previous tumor(s).


Protecting Against Anemia
The importance of maintaining or enhancing the oxygen-carrying capacity of blood cannot be overemphasized. Blood oxygen-carrying capacity may be the single most important factor in determining whether chemotherapy is successful.

In response to a low-oxygen environment, cancer cells send out growth signals that result in increased angiogenesis (blood vessel growth into the tumor). Oxygen deprivation not only induces angiogenesis, but also causes cancer cells to express additional survival factors that make them highly resistant to the toxic effects of chemotherapy.

It is an established fact that a low-oxygen environment (hypoxia) promotes tumor growth. If nothing else in this protocol is followed, correcting a hypoxic state could vastly enhance the odds of long-term survival.

The first step in correcting hypoxia is to guard against anemia. Anemia is common in cancer patients, and the result is that less oxygen is delivered to the tumor, that is, hypoxia occurs. The importance of avoiding anemia is well established in scientific literature. A study was conducted to systematically review and obtain an estimate of the effect of anemia on the survival of cancer patients. This study found that the increased risk of mortality in cancer patients who were anemic was an astounding 65% (Caro et al. 2001)!

Chemotherapy often induces anemia that then exacerbates hypoxia in the tumor. The best way of evaluating blood oxygen-carrying capacity is to measure hematocrit and hemoglobin levels. These are standard components of the complete blood count (CBC) test that should be routinely performed in all cancer patients.

Since cancer cells thrive in a hypoxic environment, the cancer patient’s hematocrit and hemoglobin should be maintained in the upper one-third of normal range prior to the initiation of chemotherapy. Table 1 describes the optimal ranges of hematocrit and hemoglobin for cancer patients.

Table 1: Optimal Ranges of Cancer Patients’ Hematocrit and Hemoglobin Levels
Based on findings from survival studies, cancer patients should fall within the optimal ranges of the following two blood tests that measure the oxygen-carrying capacity of blood:
Blood measure Normal Laboratory Reference Range Optimal Range For Cancer Patients
Hemoglobin (men) 12.5-17 grams/dL 15.5-17 grams/dL
(women) 11.5-15 grams/dL 13.83-15 grams/dL
Hematocrit (men) 36-50% 45-50%
(women) 34-44% 41-44%
Normal reference ranges based on Labcorp’s standards as of May 14, 2002.

Hypoxia (low oxygen) promotes tumor growth by inducing angiogenesis and causing cancer cells to express survival factors that interfere with the ability of chemotherapy to kill them. Chemotherapy drugs are supposed to promote apoptosis. In a hypoxic environment, however, cancer cells develop survival mechanisms that protect them against apoptosis.

There are nutrients that help improve anemic states, but any cancer patient who does not have his or her hematocrit and hemoglobin in the upper one-third of the normal range (as described in Table 1) should consider the drug Procrit (or Epogen) to achieve such levels. Procrit is a natural erythropoietin that stimulates the production of red blood cells. There is also a new long-acting erythropoietin agent approved by the FDA called Aranesp, which allows dosing every 2 weeks instead of weekly injections.

If an oncologist fails to address anemia, the patients should assume the role of advocate, demanding that attention be paid to the quality of his blood counts.

A problem that cancer patients will encounter is that oncologists normally view low blood counts as normal in cancer patients and are reluctant to prescribe Procrit unless anemia is demonstrated. Because Procrit is an expensive drug, most insurance companies refuse to pay for it unless a cancer patient is severely anemic (<10g/dL). Remember, anemia means hematocrit and hemoglobin are below the low-normal laboratory reference ranges. A cancer patient, on the other hand, should aim to have levels in the high upper-third range of normal for hematocrit and hemoglobin. Some insurance companies will not pay for Procrit until hematocrit levels are at least 20% below the lowest normal range. Is it any wonder that chemotherapy fails for so many cancer patients?

Since most insurance companies will not pay for Procrit for the purpose of boosting hematocrit and hemoglobin to the upper ranges of normal, patients may have to pay for this drug as an out-of-pocket expense. The first hurdle is convincing the oncologist to prescribe Procrit. The good news is that most cancer patients may only need Procrit for a few months, so the high cost does not have to be borne indefinitely.

The Life Extension Foundation has located pharmacies that will sell Procrit at lower prices. If your insurance company will not reimburse for this costly drug, call             (800) 544-4440 begin_of_the_skype_highlighting (800) 544-4440 end_of_the_skype_highlighting for referrals to pharmacies that may charge less than conventional retail prices.


Inhibiting the COX-2 Enzyme
Some progressive oncologists are prescribing cyclooxygenase-2 (COX-2) inhibitor drugs along with chemotherapy to improve the odds of successful treatment. COX-2 is an enzyme that many types of cancers use in order to propagate. COX-2 and its byproducts such as prostaglandin E2 (PGE2) have been shown to help fuel the growth of cancers such as colon, pancreas, estrogen-negative breast, prostate, bladder, and lung cancer.

Drugs that inhibit the cyclooxygenase enzyme are known as COX-2 inhibitors. Celebrex and Vioxx are two popular COX-2 inhibitors. Both Celebrex and Vioxx are nonsteroidal anti-inflammatory drugs (NSAIDs) that are usually prescribed to treat the symptoms of rheumatoid arthritis and osteoarthritis. There appears to be more research about Celebrex in the treatment of cancer than Vioxx.

Since chemotherapy can cause gastrointestinal bleeding, careful physician monitoring is needed when using a COX-2 inhibiting drug such as Celebrex. Caution is urged for those with known kidney disease, poor heart-lung function, liver disease, or susceptibility to stress-induced ulcers. The protocol entitled Cancer Treatment: The Critical Factors has a detailed description of the connection between COX-2 and cancer and why inhibiting the COX-2 enzyme is so important in treating many cancers.

In 1996, Life Extension recommended that most cancer patients take a COX-2 inhibiting drug because of solid evidence that cancer cells use the COX-2 enzyme to sustain their rapid division. In 1996, Americans had to import a COX-2 inhibitor named nimesulid from other countries because this class of drug was not widely available in the United States.

Experiments in laboratory animals suggest that drugs such as Celebrex could help cure cancer, especially if combined with chemotherapy or radiation (Hsueh et al. 1999; Pyo et al. 2001; Swamy et al. 2002). There are 100 separate cancer studies involving COX-2 inhibitors going on worldwide at this time.

Doctors are predicting that COX-2 inhibiting drugs may become standard therapy in 5-10 years. There was adequate evidence in 1996, however, to recommend COX-2 inhibiting drugs available to cancer patients. There are three potent COX-2 inhibiting drugs on the American marketplace. You may ask your physician to prescribe one of the following COX-2 inhibitors:

Lodine XL, 1000 mg once a day or
Celebrex, 200-400 mg every 12 hours or
Vioxx, 12.5-25 mg once a day

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Cancer Chemotherapy


Controlling Cancer Cell Growth
A family of proteins known as ras oncogenes often governs the regulation of cancer cell growth. The Ras family is responsible for modulating the regulatory signals that direct the cancer cell cycle and rate of proliferation. Mutations in genes encoding Ras proteins have been intimately associated with unregulated cell proliferation, that is, cancer.

There is a class of cholesterol-lowering drugs known as statins that has been shown to inhibit the activity of Ras oncogenes. Some of these cholesterol-lowering drugs are lovastatin, simvastatin, and pravastatin (Ura et al. 1994; Narisawa et al. 1996; Tatsuta et al. 1998; Wang et al. 2000; Furst et al. 2002; van de Donk et al. 2002).

In advanced primary liver cancer (hepatoma or hepatocellular carcinoma), patients who received 40 mg of pravastatin survived twice as long compared to those who did not receive this statin drug (Kawata et al. 2001). Interestingly, statins are also associated with the preservation of bone structure and improvement in bone density (Edwards et al. 2000; 2001; Pasco et al. 2002).

Some types of cancer (breast and prostate) have a proclivity to metastasize to the bone (Waltregny et al. 2000; Pavlakis et al. 2002). This results in bone pain that also may be associated with weakening of the bone and an increased risk of fractures (Papapoulos et al. 2000; Plunkett et al. 2000). Patients with prostate cancer, for example, are found to have a very high incidence of osteoporosis even before the use of therapies that lower the male hormone testosterone (Berruti et al. 2001; Smith et al. 2001).

In prostate cancer, when excessive bone loss is occurring, there is a release of bone-derived growth factors, for example, TGF-b1 (transforming growth factor-beta 1), that stimulate the prostate cancer cells to grow further (Reyes-Moreno et al. 1998; Shariat et al. 2001). In turn, prostate cancer cells elaborate substances such as interleukin-6 (IL-6) that facilitates the further breakdown of bone (Paule 2001; Garcia-Moreno et al. 2002). Thus, a vicious cycle results: bone breakdown-stimulation of prostate cancer cell growth that results in production of IL-6 and other cell products, which leads to further bone breakdown. When there is a breakdown of bone, the growth factors released can fuel cancer cell growth. (All cancer patients should refer to the Osteoporosis protocol in order to optimally maintain bone integrity and prevent the release of these cancer cell growth factors. The Prostate Cancer protocol has an extensive discussion about the importance of maintaining bone integrity.)

As far as statin drug dosing, higher amounts than are required to lower cholesterol are suggested for a period of several months. Cancer patients, for instance, have used 80 mg a day of lovastatin (Mevacor). This should be considered during chemotherapy in some cases. A monthly SMAC/CBC blood test is also recommended while taking a statin drug to monitor liver function. A rare potential side effect that can occur with the use of statin drugs is a condition known as rhabdomyolysis in which muscle cells are destroyed and released into the bloodstream. If muscle weakness should occur, alert your doctor so you can have a creatine kinase (CK) test to determine if muscle damage has occurred.


Combining a COX-2 Inhibitor with a Statin Drug and Chemotherapy
Depending on the type of cancer, a logical approach would be to combine a statin (such as Mevacor) with a COX-2 inhibitor and the appropriate dosing of chemotherapy.

Mevacor augmented up to five-fold the cancer-killing effect of the COX-2 inhibitor Sulindac (Agarwal et al. 1999). In this study, three different colon cancer cell lines were induced to undergo apoptosis by depriving them of COX-2. When Mevacor was added to the COX-2 inhibitor, the kill rate increased five-fold.

Physician involvement is essential to mitigate potential side effects of these drugs. Those who are concerned about potential toxicity should take into account the fact that the types of cancers that these drugs might be effective against have extremely high mortality rates. Please note that the use of statin drugs and COX-2 inhibitors for cancer is considered an off-label use of these drugs. You may ask your doctor to prescribe one of the following statin drugs to inhibit the activity of Ras oncogenes:

Mevacor (lovastatin), 40 mg twice a day or
Zocor (simvastatin), 40 mg twice a day or
Pravachol (pravastatin), 40 mg once a day

In addition to statin drug therapy, consider supplementing with the following nutrients to further suppress the expression of Ras oncogenes:

Fish Oil Capsules: 2400 mg of EPA and 1800 mg of DHA a day. (Seven Super Omega-3 EPA/DHA fish oil capsules provide this potency.)

Green Tea Extract: 1500 mg of tea polyphenols a day. (Three Mega Green Tea Extract Caps provide this potency.)

Aged Garlic Extract: 2000 mg a day. (Four Kyolic® Reserve Aged Garlic Extract™ capsules provide this potency.)


Should Antioxidants Be Taken at the Same Time as Chemotherapy?

There is a controversy as to whether cancer patients should take antioxidant supplements at the same time that cytotoxic chemotherapy drugs are being administered.

Proponents of antioxidants point to human studies showing that antioxidant supplements protect healthy cells from the damaging effects of chemotherapy drugs. Chemotherapy drugs can cause lethal heart muscle damage in a small percentage of cancer patients. Antioxidants such as vitamin E, coenzyme Q10 (CoQ10), N-acetyl-cysteine (NAC), glutathione, retinoids, ginkgo biloba, and vitamin C have been shown to specifically protect against chemotherapy-induced heart muscle damage (Tajima 1984; Mortensen et al. 1986; Iarussi et al. 1994; De Flora et al. 1996; D’Agostini et al. 1998; Schmidinger et al. 2000; Agha et al. 2001; Prasad et al. 2001; Blasiak et al. 2002). Other antioxidants have been shown to protect kidneys, bone marrow, and the immune system against chemotherapy toxicity.

Those who argue against antioxidant supplementation during chemotherapy are concerned that antioxidants will protect cancer cells against free-radical-induced destruction. Chemotherapy drugs work by varying mechanisms to induce cellular death. Some chemotherapy drugs kill cells by inflicting massive free-radical damage, while other chemotherapy drugs interfere with different cellular metabolic processes in order to eradicate cancer cells (and healthy cells as well). Depending on the type of cytotoxic drug used, however, antioxidants may confer protection to cancer cells during active chemotherapy.

The difficulty in reaching a consensus is that there are no controlled human or animal studies comparing the effects of various chemotherapy drugs, with and without antioxidants, against different cancers. The issue is complicated by studies showing that certain nutrients are associated with improved survival in cancer patients.

One problem is that there is little data to indicate whether supplements that have been shown to benefit the cancer patient should be taken during active chemotherapy. In other words, we know that anti-oxidants protect against chemotherapy side effects and may improve long-term survival in cancer patients, but do they lower the odds of achieving a long-term remission when administered during active chemotherapy?

Cancer patients contemplating cytotoxic chemotherapy are thus faced with a dilemma. They can take antioxidant nutrients to protect their healthy cells against the toxic effects of chemotherapy, or they can avoid all antioxidants during chemotherapy to possibly improve the chances that the chemotherapy drugs will kill enough cancer cells to induce a complete response or cure.

To further complicate matters, certain supplements have proven mechanisms that could augment the cytotoxic efficacy of chemotherapy. For instance, curcumin has been shown to suppress growth factors that cancer cells use to escape eradication by chemotherapy drugs. (A complete description of curcumin’s potential synergistic benefits with chemotherapy drugs appears later in this protocol.) The problem is that curcumin is also a potent antioxidant, and one recent animal study shows that curcumin could interfere with the cancer cell-killing effect of certain chemotherapy drugs. The scientists who authored this study pointed out that while curcumin has demonstrated potent effects in preventing cancer, its use during active chemotherapy is questionable because of its ability to protect cells against the type of molecular damage inflicted by these chemotherapy drugs (Somasundaram et al. 2002).

Critics of this study point out that the low dose of curcumin used in this animal study was adequate to provide antioxidant protection to the cancer cells but not high enough to suppress growth factors that enable cancer cells to escape regulatory control by the chemotherapy drugs. It was also pointed out that not all chemotherapy drugs kill cancer cells by generating free radicals. This means that curcumin may not hinder other chemotherapy drugs, as evidenced by remarkable tumor regressions found in other animal studies and human case histories.

Due to the multiple molecular complexities of this issue and the lack of specific in vivo studies, cancer chemotherapy patients are faced with choosing one of the following options:


Option One: Two weeks prior to the initiation of a chemotherapy regimen, discontinue all antioxidant supplements until 2-3 weeks after the last chemotherapy session. Most chemotherapy sessions are scheduled to last for 6-8 weeks.

The risk in depleting your body of antioxidants is that healthy cells will not be as well protected against the toxic effects of chemotherapy. This means that depending on the chemotherapy drug used, you could experience organ damage. You may also have increased immune impairment that could weaken your ability to fight the cancer. The toxic side effects of chemotherapy drugs can be the direct cause of death in some patients. Those who choose to deplete their bodies of certain antioxidants will also lose the potential benefit that these nutrients may have on cancer calls. These nutrients help prevent cancer cells from developing escape mechanisms that enable them to develop resistance to chemotherapy and other anticancer drug(s). The potential benefit is that the chemotherapy drug(s) might work better if these antioxidants are not present.


Option Two: Continue taking antioxidant supplements recommended in this and the Cancer Adjuvant Treatment protocol before, during, and after the chemotherapy is administered.

The risk is that these antioxidants could interfere with the cell-killing effects of the chemotherapy drugs. This is no small risk because cancer patients who need chemotherapy usually have only one opportunity to eradicate enough cancer cells to experience a long-term remission or cure. Cancer cells not killed by the first round of chemotherapy may become highly resistant to future.

As stated earlier, it is important to note that not all chemotherapy drugs function by inducing free-radical damage to the cancer cells. In fact, many cytotoxic chemotherapy drugs function by alternative toxic actions such as interfering with DNA/RNA synthesis (the antimetabolites), disrupting the microtubular network (microtubule inhibitors), and inhibiting chromatin function (topoisomerase inihibitors). To help a cancer patient understand the mechanism of action of common cytotoxic chemotherapy drugs, we have provided Table 2.

Table 2: How Different Chemotherapy Drugs Kill Cancer Cells
Drug Trade Name Mechanism of Action
Chemotherapy drugs that kill cancer cells by inflicting free-radical damage:
Alkylating agents Free-radical damage
Busulfan
Carboplatin
Carmustine
Chlorambucil
Cisplatin
Cyclophosphamide
Ifosfamide
Procarbazine
Myleran
Paraplatin
BiCNU
Leukeran
Platinol
Cytoxan
Ifex
Matulane
Anthracyclines Free-radical damage
Bleomycin
Doxorubicin
Daunorubicin
Epirubicin
Mitomycin C
Blenoxane
Adriamycin
Cerubidine
Ellence
Mutamycin
Plant alkaloids Free-radical damage
Teniposide
VP-16
Vumon
Etoposide
Chemotherapy drugs that kill cancer cells by other mechanisms:
Antimetabolites Inhibition of DNA/RNA synthesis
Asparaginase
Azacitidine
Cladribine
Cytarabine
Fludarabine
Fluorouracil
Hydroxyurea
Mercaptopurine
Methotrexate
Pentostatin
Ralitrexed
Thioguanine
Elspar
Mylosar
Leustatin
Cytosar
Fludara
Adrucil
Hydrea
Purinethol
Abitrexate
Nipent
Tomudex
Lanvis
(Analog of the vitamin folic acid)
Topoisomerase inhibitors Inhibition of chromatin function
Bleomycin
Dactinomycin
Daunorubicin
Doxorubicin
Epirubicin
Etoposide
Gemcitabine
Idarubicin
Irinotecan
Mitoxantrone
Plicamycin
Teniposide
Topotecan
Blenoxane
Cosmegen
Cerubidine
Adriamycin
Ellence
Vepesid
Gemzar
Idamycin
Camptosar
Novantrone
Mithramycin
Vumon
Hycamtin
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase I
Inhibition of topoisomerase II
Inhibition of topoisomerase I
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase II
Inhibition of topoisomerase I
Microtubule inhibitors Inhibition of chromatin function
Docetaxel
Paclitaxel
Teniposide
Vinblastine
Vincristine
Vinorelbine
VP-16
Taxotere
Taxol
Vumon
Velban
Oncovin
Navelbine
Etoposide

Mitotic arrest through binding of
microtubules and spindle precursors
Mitotic arrest through binding of
microtubules and spindle precursors

Table 2 provides some understanding of the mechanisms of action of chemotherapy drugs. Based on this information, it might appear that one could make a determination as to whether to take antioxidants based on the type of chemotherapy drug(s) used. Regrettably, there are other pathways (in addition to those listed) by which chemotherapy drugs induce cancer cell apoptosis that could be interfered with by taking the wrong dose of antioxidants. As already indicated, it is not possible to reach a scientific consensus as to which option to choose, that is, antioxidants or no antioxidants during active chemotherapy. There are too many variables such as the type of cancer, category of chemotherapy drug(s), molecular makeup of the cancer cells, individual variability, etc., to provide a conclusive recommendation for or against antioxidant supplementation during chemotherapy.

Cancer patients often take antioxidant supplements based on published studies showing that antioxidants help prevent cancer. Although some nutrients have been shown to reverse precancerous lesions, antioxidants alone are not a cure once cancer develops. There is persuasive evidence, however, that certain antioxidant supplements are effective in the adjuvant treatment of cancer. In other words, these supplements may help conventional therapies work better. What is missing is evidence of the effects of antioxidants in cancer patients undergoing aggressive chemotherapy.

For further guidance on the issue of whether chemotherapy patients should take antioxidant supplements, there is an extensive discussion among experts about the pros and cons of this topic in the protocol entitled Cancer: Should Patients Take Dietary Supplements?

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Cancer Chemotherapy


MAKING CHEMOTHERAPY DRUGS WORK MORE EFFECTIVELY

The dose-delivery schedule of chemotherapy drugs can determinate their efficacy in killing cancer cells and the degree of toxicity to the patient. Conventional chemotherapy treatment often uses a maximum tolerated dose (MTD) of chemotherapeutic drugs, typically administered on a schedule that varies from once a week to every 21 days, allowing a period of rest so that healthy tissue has a chance to recover. Unfortunately, while the MTD schedule is convenient for oncologists, allowing them to squeeze more patients each month into their chemotherapy unit, the rest period enables cancer cells to recover and develop survival mechanisms such as new blood vessel growth into the tumor. This means that when the next high dose of chemotherapy is given 7-21 days later, the cancer cells have become more resistant. The administration of the MTD also exposes healthy tissues to more damage.

Some studies indicate that a better approach would be to lower the dose of conventional cytotoxic agents, reschedule their application, and combine chemotherapy drugs with antiangiogenesis agents to effectively interfere with cancer’s various growth pathways and inhibit the production of blood vessels (Holland et al. 2000) (http://www.cancer.gov/clinicaltrials/developments/anti-angio-table).

This lower-dose approach, known as metronomic dosing, uses a dosing schedule as often as every day or alternates different chemotherapy drugs every other day instead of administering them all together the same day. An amount as low as 25% of the MTD, sometimes given on alternative days in combination with various signal transduction pathway inhibitors, targets the endothelial cells making up the vessels and microvessels feeding the tumor. Tumor endothelial cells then die with much less chemotherapy than cancer cells and the side effects to healthy tissue and the patient in general are dramatically reduced (Hanahan et al. 2000).

During standard chemotherapy, the typical 21-day rest period is enough to allow the tumor endothelial cells a chance to recover. However, with tighter chemotherapy dose scheduling, the slowly proliferating endothelial cells are unable to recover. In one study, mice were given the chemotherapeutic drug vinblastine at doses far below the MTD. This dose had little effect on tumor growth in the mice. A second group of mice was given the drug DC101 that inhibits the formation of new blood vessels into tumors (by blocking the induction of vascular endothelial growth factor). In the DC101 group of mice, tumor growth was slowed, as it was with the vinblastine, but then tumor growth resumed. However, in a third group of mice, a combination of the two drugs, at the low dose, resulted in full regression of the tumors with no recurrence for 6 months (Klement et al. 2000).

The administration of low doses of conventional chemotherapy drugs on a frequent basis with no breaks enables these drugs to invoke an antiangiogenesis effect, particularly when combined with a tumor endothelial cell-specific antiangiogenic drug (Gately et al. 2001; Man et al. 2002). There are clinical studies using antiangiogenic drugs (http://www.cancer.gov/clinicaltrials/developments/anti-angio-table). As will be described later in this protocol, certain dietary supplements have also been shown to interfere with angiogenesis.

At the time of this writing, a number of animal studies suggested that chemotherapy drugs could work better if the dosing schedule were changed. Human studies are ongoing, meaning it will be difficult to convince an oncologist to incorporate metronomic dosing instead of the standard MTD. While we cannot definitively recommend metronomic (lower dose/more frequent administration) chemotherapy at this time, the results of new human studies on this subject will be posted at www.lefcancer.org.


GOING BEYOND CHEMOTHERAPY

Conventional chemotherapy drugs too often show limited efficacy. Yet there is evidence indicating that the cancer cell-killing effects of these drugs can be enhanced if additional compounds are administered to the patient.

One approach is to inhibit the overexpression of receptor sites on cancer cells, which enables these cells to bind to growth factors that allow them to become resistant to the cell-killing effects of the chemotherapy drugs. Cancer cells use these signal transduction pathways as growth vehicles to escape natural regulatory control and also to protect themselves against the cytotoxic effects of cancer drugs. The utilization of these signal transduction inhibitors enhances the potential effect of low(er) dosing of chemotherapeutic drugs.

Another therapeutic target is the endothelial cells that form new blood vessels. The process by which new blood vessels are formed is called angiogenesis, and cancer cells initiate blood vessel proliferation in order to fuel rapid growth (Hanahan et al. 2000). Agents that interfere with the formation of new blood vessels are an important part of a comprehensive treatment strategy.

Because cancer cells are stimulated to produce new blood vessels in response to a low-oxygen environment (hypoxia), the critical importance of boosting the oxygen-carrying capacity of blood was discussed earlier in this protocol.


Inhibiting Signal Transduction Pathways
All cells, both normal and cancerous, have molecular receptor sites on their surface. These sites are much like locks that may be opened or activated only by the correct molecular key. Once opened or activated, a chain of biochemical events occurs specific to that receptor. Cytokine growth factors are a class of substances that stimulate cell growth by a variety of mechanisms.

An example of such a pathway is the binding of transforming growth factor-alpha (TGF-alpha) to the epidermal growth factor receptor (EGFR) site. Such a binding is a growth pathway for many cancers, causing rapid cell proliferation. The overexpression of this pathway is also implicated in tumor cells that are resistant to cytotoxic drugs (including the interferons).

Interference with this pathway at the EGFR receptor site can effectively shut down overexpression and the subsequent cell proliferation, making the cancer much more vulnerable to therapy. Blocking the EGFR has been shown to inhibit tumor growth by interfering with cancer cell repair, tumor invasion, metastasis, and angiogenesis (Arteaga 2002; Wakeling et al. 2002).

Drugs that inhibit the EGFR showed promise in early studies but have failed in recent clinical trials when combined with cytotoxic chemotherapy drugs. One of these EGFR inhibiting drugs is Iressa. One reason that Iressa and a similar-acting drug named Erbitux failed in human clinical studies is that an inadequate combination and dosing schedule of chemotherapy drugs may have been used to kill the cancer cells. Drugs such as Iressa will not cure cancer by themselves, but they could be of benefit if metronomic-dosing chemotherapy were used and/or during immune-augmentation therapy if they were used with drugs such as alpha interferon.

The objective of blocking the signal transduction pathway is to prevent cancer cells from mutating in a way that enables them to avoid destruction.


Natural Signal Transduction Inhibitors
As noted, molecular evidence and animal studies suggest that agents that inhibit certain growth signals used by cancer cells might work synergistically with metronomic cycled chemotherapy or be useful as post chemotherapy agents along with immune-augmentation therapy.

There are natural signal transduction inhibitors available, but because most of them are potent antioxidants, some cancer patients may choose to wait 2-3 weeks after chemotherapy ends to start using them.

Soy (genistein) extract is known to inhibit the epidermal growth factor (EGF) receptor via an interference with the TGF-alpha pathway (Bhatia et al. 2001).

Genistein is also known to block the induction of the basic fibroblast growth factor (bFGF), a potent growth and angiogenic factor in cancers such as renal cell carcinoma and malignant melanoma (Hurley et al. 1996). Additionally, genistein is known to block induction of the vascular endothelial growth factor (VEGF) considered essential for angiogenesis and tumor endothelial cell survival (Mukhopadhyay et al. 1995).

The blockade of the overexpression of the EGF receptor and the inhibition of the signaling pathways, bFGF and VEGF, is dose-dependent response. Soy genistein may be an effective adjuvant to conventional or metronomic chemotherapy, but human clinical studies are lacking, which is unfortunately the case with most nonpatented natural therapies. There is a controversy about the use of soy as a cancer treatment. A complete description of the pros and cons of high-dose genistein therapy can be found in the Cancer Adjuvant Therapy protocol.

Curcumin, an extract of the spice turmeric, is synergistic with genistein and inhibits angiogenic growth signals emitted by tumor cells. Curcumin acts via a different mechanism than genistein to inhibit the EGF receptor but is up to 90% effective in a dose-dependent manner. It is important to note that while curcumin has been shown to be up to 90% effective in inhibiting the expression of the EGF receptor on cancer cell membranes, this does not mean that it will be effective in 90% of cancer patients or reduce tumor volume by 90%. Because two-thirds of all cancers, however, over-express the EGR receptor and such overexpression frequently fuels the metastatic spread of cancer throughout the body, the suppression of this receptor is desirable.

Curcumin has a number of other antiangiogenic properties that appear to be synergistic with metronomic dosing chemotherapy. These potential synergistic and/or additive mechanisms include:

  • Inhibition of the induction of basic fibroblast growth factor (bFGF). bFGF is both a potent mitogen (growth signal) for many cancers and an important signaling factor in angiogenesis (Arbiser et al. 1998).
  • Inhibition of the induction of hepatocyte growth factor (HGF), overexpression is involved in hepatocellular (liver cell-related) carcinoma (Seol et al. 2000).
  • Inhibition of the expression of COX-2, the enzyme involved in the production of PGE-2, a tumor-promoting prostaglandin (Zhang et al. 1999).
  • Inhibition of a transcription factor in cancer cells known as nuclear factor-kappa B (NF-KB). Many cancers overexpress NF-KB and use this as a growth vehicle to escape regulatory control (Plummer et al. 1999).
  • Increased expression of nuclear p53 protein in human basal cell carcinomas, hepatomas, and leukemia cell lines, which increases apoptosis (Jee et al. 1998).


Why Agents That Inhibit Angiogenesis and Block Signal Transduction Are Failing
Based on the multiple favorable mechanisms listed, higher-dose curcumin would appear to be useful for cancer patients. There are contradictions in scientific literature concerning curcumin intake at the same time as chemotherapy drugs. Some studies indicate enhanced benefit, whereas other studies hint at reduced benefit and even potential toxicity. The anticancer drug cisplatin is strongly enhanced with curcumin, (Navis et al. 1999), yet cisplatin kills cancer cells by generating free radicals, and curcumin is an antioxidant. Another study showed that low-dose curcumin inhibited camptothecin-, mechlorethamine-, and doxorubicin-induced apoptosis of several different human breast cancer cells. This same study showed that curcumin inhibited cyclophosphamide-induced breast tumor regression in an in vivo animal model (Somasundaram et al. 2002). Another in vitro study involving curcumin’s concomitant use with the chemotherapy drug Irinotecan indicated potential toxicity (Michaels et al. 2001), yet in and of themselves chemotherapy drugs are inherently toxic.

Whether high-dose curcumin is beneficial or detrimental depends on the type and dose of the chemotherapeutic drug used, the kind of cancer cell, and the dose of the curcumin. Until more definitive information is published, we prefer to err on the side of caution and recommend that chemotherapy patients wait 3 weeks after their last dose of chemotherapy before taking high-doses of curcumin.

Pharmaceutical companies are investing billions of dollars to develop drugs proven to interfere with cancer cell growth. Unfortunately, these drugs have failed to extend survival in late-stage cancer patients. In some of these clinical studies, tumor shrinkage is observed, but the patients still die. Experts remain convinced, however, that these drugs will eventually play a significant role in the treatment of cancer.

One reason these drugs are not working is that they usually suppress only one of the growth factors that cancer cells use to escape regulatory control. Scientists know of more than 20 growth factors used by tumors. Late-stage breast cancer cells, for example, may express as many as six different growth factors that induce angiogenesis. Cancer cells emit these growth factors to draw new blood vessels into tumors and/or overexpress the EGF receptor.

Human studies have tested angiogenesis inhibitors or EGF receptor blockers on late-stage patients whose cancer cells have mutated to become highly resistant. If these drugs were tested earlier in the disease process, some physicians believe they would work better. One problem is that the FDA restricts the testing of new cancer drugs to only patients who have failed all other proven therapies. Regrettably, we know that cancer cells mutate each time they are exposed to a new therapy. By testing new cancer drugs only on patients who have failed previous therapy, a tremendous burden of efficacy is being placed on these new compounds, that is, these drugs are expected to kill cancer cells in their most aggressive stages.

Some experts note that ultimately successful treatment using antiangiogenesis and signal transduction blockers may depend on the use of a multidrug cocktail, one that
would block all known growth factors used by cancer cells. That would parallel the success in treating AIDS, in which several antiviral drugs that work by different mechanisms are combined into cocktails that have turned the condition into a manageable disease for some people.

Based on current knowledge, it would appear logical to simultaneously test a wide range of angiogenesis inhibitors and signal transduction pathway blockers on early-stage cancer patients. Such testing might be considered at the time that other cytotoxic therapies are administered or shortly thereafter.

The potential advantage of combining high potency genistein, curcumin, and green tea extracts is that they have been shown to suppress a wide variety of growth factors used by cancer cells. Considering the enormous cost of testing drugs that work in similar ways to genistein, curcumin, and green tea, it is doubtful that these nonpatented natural agents will be tested on cancer patients in the near future. The cancer patient is thus faced with deciding whether or not to incorporate these natural agents into their overall treatment program based on the data currently available.


Inhibiting Angiogenesis
Angiogenesis provides nourishment for the tumor’s rapid propagation. Antiangiogenesis agents inhibit this new tumor blood vessel growth and are being studied as potential cancer therapies. As noted, genistein and curcumin have demonstrated molecular effects involved in the inhibition of new blood vessel growth into tumors. An extract from green tea may also be an effective antiangiogenesis agent.

The primary action of green tea is through its catechin, epigallocatechin gallate (EGCG), which blocks the induction of vascular endothelial growth factor (VEGF), considered essential in angiogenesis and tumor endothelial cell survival. In vivo studies have shown green tea extracts to have the following actions on human colon cancer cells:

Inhibition of tumor growth 58%
Inhibition of microvessel density 30%
Inhibition of tumor cell proliferation 27%
Increased tumor cell apoptosis 1.9-fold
Increased tumor endothelial cell apoptosis three-fold
(Jung et al. 2001b.)

The optimal dose of green tea, soy, and curcumin and when they should be taken will be discussed later in this protocol. Please note that EGCG is a powerful antioxidant, as are other polyphenols found in green tea. Some chemotherapy patients may choose to wait 3 weeks after chemotherapy has ended to initiate green tea (EGCG) supplementation.

As indicated near the beginning of this protocol, the most effective way of inhibiting tumor angiogenesis may be by guarding against hypoxia. It is crucial for cancer patients to maintain their blood oxygen-carrying capacity (as measured by hematocrit and hemoglobin) in the upper range of normal.

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Cancer Chemotherapy


MITIGATION OF CHEMOTHERAPY SIDE EFFECTS

Cancer chemotherapy is known to produce severe side effects such as heart muscle damage, gastrointestinal damage, anemia, nausea, and lethal suppression of immune function.

Nutrients and hormone therapies can be used to mitigate the toxicity of chemotherapy. Bolstering the immune system may help alleviate or reduce the severity of the complications associated with chemotherapy. As discussed earlier in this protocol, however, using natural antioxidants to protect against chemotherapy side effects could possibly reduce the cancer cell-killing efficacy of the cytotoxic drug(s). Regrettably, there are no survival studies to verify the long-term effects of using natural therapies to mitigate the toxic effects that chemotherapy inflicts on healthy normal cells. In other words, we know that certain nutrients can protect normal cells against the immediate toxic effects of chemotherapy, but we do not know if this protection extends to cancer cells in such a way as to diminish cancer cell death.

For those who choose to use antioxidants to protect against chemotherapy side effects, supplementation with these nutrients should be initiated several days or even weeks before any planned chemotherapy is begun and should be continued well after the chemotherapy has been completed.


Vitamins E and C and N-Acetyl-Cysteine
Vitamins E and C and N-acetyl-cysteine (NAC) can protect against heart muscle toxicity for cancer patients undergoing high doses of chemotherapy. A controlled study examined the effects of these nutrients on cardiac function on a group of chemotherapy and radiation patients. One group was given supplements of vitamins C and E and NAC, while the other group was not supplemented. In the group not supplemented, left ventricle function was reduced in 46% of the chemotherapy patients compared to those who took the supplements. Furthermore, none of the patients from the supplement group showed a significant fall in overall ejection fraction, but 29% of the nonsupplement group showed reduced ejection fraction (Wagdi et al. 1996).

Vitamin C improved the antineoplastic activity of the chemotherapeutic drugs doxorubicin, cisplatin, and paclitaxel in human breast carcinoma cells. Patients reported improved appetite while taking vitamin C, as well as a reduced need for painkillers.

Vitamin E has been shown to protect against cardio-myopathies induced by chemotherapy. Vitamin E has also been used in combination with vitamin A and CoQ10 to reduce the side effects of the chemotherapy drug Adriamycin (doxorubicin). Vitamin E is complementary to chemotherapy in that it boosts the effectiveness of these drugs. One study showed enhanced efficacy of both 5-FU and doxorubicin against human colon cancer cells, with vitamin E supplementation (Chinery et al. 1997).

Note: Fluorouracil, or 5-FU, is an antineoplastic agent used in the palliative management of certain cancers.

The mechanism of action of vitamin E appears to be the induction of the tumor suppressor protein p21. The dry powder succinate form of vitamin E appears to be most beneficial to cancer patients. The more common acetate form has proven ineffective in slowing cancer cell growth in some test tube studies, whereas natural dry powder vitamin E succinate has shown efficacy (You et al. 2001).

Still another study specifically suggested that cancer patients treated with Adriamycin should supplement with vitamins A and E and selenium to reduce its toxic side effects (Faure et al. 1996).


CoQ10
CoQ10 is used with vitamin E to protect patients from chemotherapy-induced cardiomyopathies. CoQ10 is nontoxic even at high dosages and has been shown to prevent liver damage from the drugs Mitomycin C and 5-FU. Adriamycin-induced cardiomyopathies have been prevented by concomitant supplementation with CoQ10.

Caution: Some studies indicate that CoQ10 should not be taken at the same time as chemotherapy. If this were true, it would be disappointing because CoQ10 is so effective in protecting against Adriamycin-induced cardiomyopathy. Adriamycin is sometimes used as part of a chemotherapy cocktail. Until more research is known, it is not possible to make a definitive recommendation of whether to take CoQ10 during chemotherapy.


Selenium
Selenium has been used in combination with vitamin A and vitamin E to reduce the toxicity of chemotherapy drugs, particularly Adriamycin (Faure et al. 1996; Vanella et al. 1997). The synergistic effect of vitamin E and selenium together to enhance the immune system is greater than either alone. A new form of selenium is Se-methylselenocysteine (SeMSC), a naturally occurring selenium compound found to be an effective chemopreventive agent. SeMSC is a selenoamino acid that is synthesized by plants such as garlic and broccoli. SeMSC has been shown to induce apoptosis in certain ovarian cancer cells (Yeo et al. 2002) and to be effective against breast cancer cell growth both in vivo and in vitro (Sinha et al. 1999). SeMSC has also demonstrated significant anticarcinogenic activity against mammary tumorigenesis (Sinha et al. 1997).

Moreover, SeMSC is one of the most effective chemopreventive compounds, inducing apoptosis in leukemia HL-60 cell lines (Jung et al. 2001a). Some of the most impressive data suggest that exposure to SeMSC blocks clonal expansion of premalignant lesions at an early stage. This is achieved by simultaneously modulating certain molecular pathways that are responsible for inhibiting cell proliferation and enhancing apoptosis (Ip et al. 2001).

Unlike selenomethionine, which is incorporated into protein in place of methionine, SeMSC is not incorporated into any protein, thereby offering a completely bioavailable compound for preventing cancer. Therefore, 200-400 mcg of SeMSC a day is suggested for cancer patients. Please note that selenium also possesses antioxidant properties, so its use before, during, or immediately after chemotherapy could theoretically inhibit the actions of certain chemotherapy drugs.


Whey Protein
Glutathione balance is very important for the cancer patient. Glutathione is an antioxidant that protects normal cells from toxic chemotherapy drugs. Glutathione levels in cancer cells are very high and act to protect against the destructive actions of chemotherapy and radiation. Whey actually lowers the cancer cell glutathione levels, allowing the chemotherapy and radiation to be more effective at destroying cancer cells but not normal cells.

Tumor cell glutathione concentration may be among the determinants of the cytotoxicity of many chemotherapeutic agents and radiation. An increase in glutathione concentration in cancer cells appears to be at least one of the mechanisms of acquired drug resistance to chemotherapy. Whey proteins used in combination with glutathione appear to reduce the concentrations of glutathione in cancer cells, thereby making them more vulnerable to chemotherapy while maintaining or even increasing glutathione levels in normal healthy cells.

Cancer cells had reduced glutathione levels in the presence of whey protein while at the same time normal cells had increased levels of glutathione levels with increased cellular growth of healthy cells. Selective depletion of tumor GSH may render malignant cells more vulnerable to the action of chemotherapeutic agents (Kennedy et al. 1995).
Glutathione production in cancer and healthy cells is negatively inhibited by its own synthesis. Because glutathione levels are higher in cancer cells, it is believed that cancer cells would reach a level of negative-feedback inhibition for glutathione production more easily than normal cells.

Chemotherapy patients should consider taking 30-60 grams a day of whey protein concentrate (in divided doses) 10 days before initiation of chemotherapy, during chemotherapy, and at least 10 days after the chemotherapy session is completed.

Note: If blood testing shows that chemotherapy has suppressed the immune system, patients should insist that their oncologists use the appropriate immune restoration drug(s) as outlined later in this protocol.

Whey protein concentrate selectively depletes cancer cells of their glutathione, making them more susceptible to cancer treatments such as radiation and chemotherapy (Bounous 2000; Tsai et al. 2000).


Shark Liver Oil (Not Shark Cartilage)
Chemotherapy causes a reduction in blood cell production. A natural therapy to restore healthy platelet production is 5 capsules a day of standardized shark liver oil, containing 200 mg of alkylglycerols per capsule. Shark liver oil can boost the production of blood platelets. Studies have shown the immune-enhancing capabilities of shark liver oil (Pugliese et al. 1998).

Caution: Shark liver oil capsules should be taken at a dose of 5 capsules containing 200 mg of active alkylglycerols for a maximum duration of 30 days. A complete blood count (CBC) and platelet count should be obtained weekly to monitor the effectiveness of shark liver oil and to prevent against excessive platelet production, that is, values greater than 400,000. Platelet counts exceeding 400,000 have been associated with increased risks of both thrombosis and hemorrhage.


Melatonin
Melatonin has been shown to protect against chemotherapy-induced immunosuppression. Melatonin mediates the toxicity of chemotherapy and inhibits free-radical production (Lissoni et al. 1999). In a randomized study to evaluate the effect of melatonin on the toxicity of chemotherapy drugs, patients receiving melatonin with chemotherapy had lower incidences of neuropathies, thrombocytopenia, stomatitis, alopecia, malaise, and vomiting. The appropriate dose of melatonin was between 30-50 mg at bedtime (Lissoni et al. 1997a; Lissoni et al. 1997b). Adding melatonin to a chemotherapy regimen may prevent some toxic effects of the chemotherapy drugs, especially myelosuppression (suppression of blood cells production in bone marrow) and neuropathies (abnormality of nerve functioning both within and outside the central nervous system).

It is important to understand that melatonin protects against thrombocytopenia. If melatonin is considered, it should be started before chemotherapy is initiated. Melatonin may also be an especially effective and safe therapy to correct thrombocytopenia, a condition characterized by a decrease in the number of blood platelets. In patients who randomly received chemotherapy alone or chemotherapy plus melatonin (20 mg each evening), thrombocytopenia was significantly less frequent in patients treated with melatonin (Lissoni 2002).

Malaise and lack of strength were also significantly less frequent in patients receiving melatonin. Finally, stomatitis (inflammation of the mouth area) and neuropathy were less frequent in the melatonin group. Alopecia and vomiting were not influenced (Lissoni et al. 1997b). Administration of melatonin during chemotherapy may prevent some chemotherapy-induced side effects, particularly myelosuppression and neuropathy.

Oncologists often prescribe drugs (Leukine) that work in a similar way as melatonin to protect the immune system. Leukine, for instance, is a granulocyte/macrophage colony-stimulating factor drug that can restore immune function debilitated by toxic cancer chemotherapy drugs. If you are on chemotherapy and your blood tests show white blood cell immune suppression, you should request the appropriate immune restoration drug (such as Leukine or Neupogen) from your medical oncologist.

Studies have shown that melatonin specifically exerts colony-stimulating activity and rescues bone marrow cells from apoptosis induced by cancer chemotherapy compounds. The number of granulocyte/macrophage colony-forming units has been shown to be higher in the presence of melatonin; the dose used was between 30-50 mg nightly (Maestroni et al. 1994a; 1994b; 1998).

Melatonin enhances the anticancer action of interleukin-2 (IL-2) and reduces IL-2 toxicity when used in combination. Melatonin used in association with IL-2 cancer immunotherapy has been shown to have the following actions:

  1. Amplification of IL-2 biological activity by enhancing lymphocyte response and by antagonizing macrophage-mediated suppressive events
  2. Inhibition of production of tumor growth factors that stimulate cancer cell proliferation by counteracting lymphocyte-mediated tumor cell destruction
  3. Maintenance of a circadian rhythm of melatonin, which is often altered in human neoplasms and influenced by cytokine injection

The subcutaneous administration of 3 million IU a day of IL-2 and high doses of melatonin (40 mg each evening orally) has appeared to be effective in tumors resistant either to IL-2 alone or to chemotherapy. The dose of 3 million IU a day of IL-2 is a low dose, while serious toxicity normally begins at 15 million IU a day.

European oncologists have treated numerous end-stage solid tumor patients with the melatonin/IL-2 combination. The conclusion drawn from clinical studies is that melatonin protects against IL-2 toxicity and synergizes with the anticancer action of IL-2 (Conti et al. 1995). The combination strategy was shown to be a well-tolerated therapy to control tumor growth.

In the largest clinical study to date, the effects of melatonin were evaluated in 1440 patients with untreatable advanced solid tumors. One group received supportive care alone, while the other group received supportive care plus melatonin. In a second study, the influence of melatonin on the efficacy and toxicity of chemotherapy was evaluated in 200 metastatic patients with chemotherapy-resistant tumors. These patients were randomized to receive chemotherapy alone or chemotherapy plus melatonin. In both studies, 20 mg of melatonin were given orally at night. The frequency of cachexia, asthenia, thrombocytopenia, and lymphocytopenia was significantly lower in patients treated with melatonin compared to those who received supportive care alone.

Moreover, the percentage of patients with disease stabilization and the percentage one-year survival rate were both significantly higher in patients concomitantly treated with melatonin than in those treated with supportive care alone. The objective tumor response rate was significantly higher in patients treated with chemotherapy plus melatonin than in those treated with chemotherapy alone. In addition, melatonin induced a significant decline in the frequency of chemotherapy-induced asthenia, thrombocytopenia, stomatitis, cardiotoxicity, and neurotoxicity. These clinical results demonstrate that melatonin may be successfully administered in the supportive care of untreatable advanced cancer patients and for the prevention of chemotherapy-induced toxicity (Lissoni 2002).

Table 3: Summary of Studies Using Melatonin
Lissoni’s Phase II Randomized Clinical Trial Results
Tumor Type Patient Number Basic Therapy Melatonin Dose 1-Year Survival
Melatonin Placebo
Metastatic Nonsmall Cell Lung 63 Supportive Care Only 10 mg 26% Under 1%
Glioblastoma 30 Conventional Radiotherapy 10 mg 43% Under 1%
Metastatic Breast 40 Tamoxifen 20 mg 63% 24%
Brain Metastases 50 Conventional Radiotherapy 20 mg 38% 12%
Metastatic Colorectal 50 IL-2 40 mg 36% 12%
Metastatic Nonsmall Cell Lung 60 IL-2 40 mg 45% 19%
Compiled by Cancer Treatment Centers of America and published in the March 2002 issue of Life Extension magazine.


Melatonin Precautions
The Life Extension Foundation introduced the world to melatonin in 1992, and it was the Life Extension Foundation that issued the original warnings about who should not take melatonin. These warnings were based on preliminary findings, and in two instances, the Foundation was overly cautious.

First, we suggested that prostate cancer patients might want to avoid high doses of melatonin. However, subsequent studies indicated that prostate cancer patients could benefit from moderate doses of melatonin, although the Foundation still advises prostate cancer patients to have their blood tested for prolactin. Prolactin is a hormone secreted by the pituitary gland. Its role in the male has not been demonstrated, but in females, prolactin promotes lactation after childbirth.

Melatonin could possibly elevate prolactin secretion, and if this were to happen in a prostate-cancer patient, the drug Dostinex (0.5 mg twice a week) could be used to suppress prolactin so that the melatonin could continue to be taken (in moderate doses of 1-6 mg each night). Please note that the starting dose of Dostinex is 0.125 mg twice a week. If well tolerated, increase to 0.25 mg twice a week. If again well tolerated after 2 weeks, then increase to 0.5 mg twice a week while checking morning fasting prolactin levels.

Some physicians initially thought that ovarian cancer patients should not take melatonin, but a study in Oncology Reports indicated that high doses of melatonin may be beneficial in treating ovarian cancer. In this study, 40 mg of melatonin were given nightly, along with low doses of IL-2, to 12 advanced ovarian cancer patients who had failed chemotherapy. While no complete response was seen, a partial response was achieved in 16% of patients, and a stable disease was obtained in 41% of the cases (Lissoni et al. 1996). This preliminary study suggested that melatonin is not contraindicated in advanced ovarian cancer patients. It is still not known what the effects of melatonin are in leukemia; therefore, leukemia patients should use melatonin with caution.


Protecting Immune Function
Cancer patients using cytotoxic chemotherapy drugs should ask their oncologist to place them on FDA-approved immune-protective medications concurrently with chemotherapy. Leukine in particular partially restores immune cell production lost due to the toxic effects of chemotherapy. The primary benefit of Leukine is to stimulate macrophage production to prevent bacterial infection in the chemotherapy patient. Macrophages also engulf cancer cells and assist in their destruction by the immune system (Kobrinsky et al. 1999). In one study, patients with refractory (resistant to treatment) solid tumors treated with standard chemotherapy and Leukine had a 33.3% objective response rate versus 15% with chemotherapy alone (Baxevanis et al. 1997).

The timing of administration of colony-stimulating drugs such as Leukine is crucial. The oncologist should not wait until there are toxic bone marrow effects to prescribe leukine. The administration of Leukine should be timed to be initiated 24-48 hours after the last round of chemotherapy in order to prevent a dangerous nadir (precipitous decline) in immune cells (granulocytes). The proper administration of Leukine can dramatically reduce the immune damage that chemotherapy inflicts on the body and increase the cancer cell-killing efficacy of conventional chemotherapy drugs.

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Cancer Chemotherapy


Enhancing Immune Function
Alpha-interferon and/or IL-2 are immune cytokines (regulators) that should be considered by some cancer patients. Interferon directly inhibits cancer cell proliferation and has been used in the therapy of hairy cell leukemia, Kaposi’s sarcoma, malignant melanoma and squamous cell carcinoma. IL-2 allows for an increase in the cytotoxic activity of natural killer (NK) cells. An oncologist must carefully administer these drugs because they can produce temporary side effects. A significant side effect of interferon is that it can leave some patients temporarily debilitated. One reason why interferon has not become popular.

A cancer patient has to weigh the benefit of achieving complete tumor eradication in relation to the debilitation occurring during the time of active therapy. A typical dose of alpha-interferon is 3 million IU administered by self-injection daily for 2 weeks. To mitigate the debilitating effects, most patients take interferon for 2 weeks and then skip 2 weeks. IL-2 has been self-administered by subcutaneous injection in the dose of 3-6 million IU a day for 5-6 days each week.

Note: Interferon has been shown to work on squamous cell carcinomas but not on common adenocarcinomas.

Retinoic acid (vitamin A) analog drugs enhance the efficacy of some chemotherapy regimens and reduce the risk of secondary cancers. These vitamin A analog drugs have been shown to work well when taken in conjunction with alpha-interferon. Ask your oncologist to consider prescribing vitamin A analog drugs such as Accutane (13-cis-retinoic acid) or Vesanoid (all-trans retinoic acid). The use of a retinoid drug therapy depends on your type of cancer. Some cancers have historically responded well to retinoid drug therapy while others have not. The tumor cell testing recommendations in the protocol Cancer Therapy: The Critical Factors can help determine whether retinoid drug therapy is appropriate. Your oncologist must carefully prescribe the use and dosage of potentially toxic retinoid drugs such as Accutane.

Some cancer patients produce too many T-suppressor cells that shut down optimal immune function. The administration of drugs such as cimetidine helps to prevent cancer cells from prematurely shutting down the immune system. Cimetidine, also known as Tagamet, is an over-the-counter medication that blocks the action of histamine on stomach cells and reduces stomach acid production. An immune cell blood test will reveal the status of your T-helper cells, T-suppressor cells, and natural killer (NK) cell count and activity. A suggested cimetidine-dosing regimen is 800 mg each night. Cimetidine also interferes with metastasis by blocking the expression of an adhesion molecule known as E-selectin that enables cancer cells to bind to blood vessel walls and start metastatic colonies.

Caution: Cimetidine may increase the toxicity of certain chemotherapy drugs. Cimetidine increased blood concentrations of the drug epirubicin used to treat breast cancer (Murray et al. 1998), while cimetidine combined with 5-fluorouracil dramatically improved survival in certain types of colon cancer (Matsumoto et al. 2002). If you are taking cimetidine, tell your oncologist so that the dose of your chemotherapy drug can be adjusted if necessary.


ANTI-NAUSEA DRUGS FOR CHEMOTHERAPY PATIENTS

Nausea is one of the most common and most difficult aspects of chemotherapy for cancer patients. Nausea can have secondary effects on cancer patients by interfering with their eating habits during and immediately after chemotherapy.

Drugs to mitigate chemotherapy-induced nausea include Kytril, Megace, and Zofran. The high cost of some of these drugs has kept many cancer patients not covered by insurance from obtaining one of these potentially beneficial drugs. If you are receiving chemotherapy and are experiencing nausea, you should be able to demand that any HMO, PPO, or insurance carrier pay for this class of drug. These drugs may enable a cancer patient to tolerate chemotherapy long enough for it to be effective.

An interesting study evaluated glutathione and vitamins C and E for their antinausea properties. Glutathione and vitamins C and E significantly reduced cisplatin-induced vomiting in dogs. The anti-nausea activity of antioxidants was attributed to their ability to react with free radicals generated by cisplatin. Ginger extract has also been shown effective in reducing nausea symptoms (Keating et al. 2002).


Aprepitant (Emend®) for Chemotherapy-Induced Nausea and Vomiting
Chemotherapy-induced acute and delayed nausea and vomiting (CINV) can occur with either an initial chemotherapy cycle or with repeated chemotherapy cycles. Cisplatin is a commonly used chemotherapy drug known to cause CINV in most patients who receive it. Cisplatin is used to slow or stop cancer cell growth in patients with metastasized testicular and ovarian tumors who have already had surgical and/or radiotherapy procedures. It is used in patients with metastasized ovarian tumors who are unresponsive to standard chemotherapy, but have not yet received cisplatin.

Patients with advanced transitional-cell bladder cancer that is no longer controlled by surgery and/or radiotherapy also receive cisplatin. The drug is given intravenously in cycles, often in combination with other chemotherapy drugs. Severe CINV usually occurs within 1 to 4 hours after administration and symptoms can continue for 24 hours or persist for up to a week. A delayed form can occur in patients who had no nausea when cisplatin was initially administered. This form begins 24 hours or more following cisplatin chemotherapy. The symptoms of cisplatin CINV are so debilitating that some patients refuse further chemotherapy treatment.

On March 26, 2003, aprepitant (Emend®) received FDA approval. Aprepitant is a drug to be used in combination with other anti-nausea/anti-vomiting drugs to prevent CINV. Standard anti-nausea therapy for CINV is dexamethasone (Decadron®, a corticosteroid) and ondansetron (Zofran®, a 5-HT3 or serotonin receptor antagonist). However, aprepitant works in combination with these anti-nausea drugs by targeting a different family of receptors in the brain associated with nausea called the NK1 receptors (neurokinin 1). A typical combination treatment regimen directed by a treating physician is:

  • Day 1: 125 mg of aprepitant orally 1 hour before chemotherapy; 32 mg of ondansetron intravenously before chemotherapy; and 12 mg of dexamethasone orally.
  • Days 2 through 4: 80 mg of aprepitant orally on days 2 and 3 only; and 8 mg of dexamethasone orally in the morning on days 2 to 4.

Aprepitant (Emend) is the first NK1 blocking drug to be approved by the FDA. FDA approval was based on the results of studies including over 1000 cancer patients who received chemotherapy that caused CINV (de Wit et al. 2003; Heskith et al. 2003; Poli-Bigelli et al. 2003). In these studies, when compared to symptoms in patients who received standard CINV medicines, the symptoms of CINV were reduced significantly when aprepitant was included with the standard medicines.

In a Phase III study (520 patients; multicenter, randomized, double-blind, placebo-controlled; endpoint of complete response) that evaluated patients for 5 days after chemotherapy, 72.7% of the patients using aprepitant had complete response on days 1 to 5 (no nausea and vomiting; no rescue therapy). This response was significantly higher than the 52.3% response in the standard therapy group (Hesketh et al. 2003). A similar Phase III study evaluated 523 patients for efficacy and 568 patients for safety for 5 days following high-dose cisplatin chemotherapy. During the 5 days after chemotherapy, patients in the aprepitant group had a complete response of 62.7% vs. 43.3% in the standard therapy group. Incidence of adverse events was similar in both groups (72.8% vs. 72.6%). In the aprepitant group, complete response ranged from 82.8% on day 1 to 62.7% on days 2 to 5 vs. 68.4% on day 1 and 46.8% on days 2 to 5 for the standard therapy group (Poli-Bigelli et al. 2003).

Another Phase III double-blind study (endpoint of complete response) enrolled 202 patients and observed them for 6 chemotherapy cycles. The group receiving aprepitant (125 mg before cisplatin and 80 mg on days 2 to 5 vs. 375 mg/250 mg) reported a complete response of 64% vs. 49% for the group receiving standard ondansetron/dexamethasone treatment. After cycle 6, the aprepitant group still had a complete response of 59% compared to 35% in the standard therapy group (de Wit et al. 2003). Researchers conducting these three studies concluded that aprepitant plus a standard regimen of odansetron and dexamethasone consistently provided superior protection from CINV compared to standard therapy alone (de Wit et al. 2003; Heskith et al. 2003; Poli-Bigelli et al. 2003). Additionally, de Wit et al. (2003) concluded that aprepitant provided sustained protection against CINV over multiple cycles of chemotherapy when existing drugs often become less effective.

A multi-center, randomized, double-blind, placebo-controlled study seeking to define the most appropriate dose regimen of oral aprepitant (375 mg/250 mg vs. 125 mg/80 mg vs. 40 mg/25 mg vs. standard therapy) was conducted in 376 patients with cancer who were receiving initial cisplatin. (While the study was ongoing, aprepitant 375 mg/250 mg was discontinued resulting from pharmacokinetic data obtained that indicated an apparent interaction with dexamethasone.) The authors concluded that an aprepitant 125-mg/80-mg regimen added to a standard regimen of intravenous ondansetron and oral dexamethasone had the most favorable benefit to risk profile (Chawla et al. 2003). Possible drug interactions with aprepitant include some chemotherapies, birth control pills (reduces effectiveness), blood thinners (Coumadin), and other drugs (e.g., Orap®, Seldane®, Hismanal®, and Propulsid®) as well as non-prescription and herbal products (Merck 2003).


NATURAL APPROACHES TO ENHANCING CHEMOTHERAPY EFFICACY


Fish Oil and Chemotherapy
Fish oil may enhance the effectiveness of cancer chemotherapy drugs. A study compared different fatty acids on colon cancer cells to see if they could enhance Mitomycin C, a chemotherapy drug efficacy. Eicosapentaenoic acid (EPA) concentrated from fish oil was shown to sensitize colon cancer cells to Mitomycin C (Tsai et al. 1997). It should be noted that fish oil also suppresses the formation of prostaglandin E2, an inflammatory hormone-like substance involved in cancer cell propagation.

In another study, a group of dogs with lymphoma were randomized to receive either a diet supplemented with arginine and fish oil or just soybean oil. Dogs on the fish oil and arginine diet had a significantly longer disease-free survival time than dogs on the soybean oil (Ogilvie et al. 2000).


Caffeine and Chemotherapy
The use of caffeine in combination with chemotherapy has been shown to enhance the cytotoxicity of chemotherapy drugs. Caffeine occurs naturally in green tea and has been shown to potentiate the anticancer effects of tea polyphenols. In SKH-1 mice at high risk of developing malignant and nonmalignant tumors, oral administration of caffeine (as sole source of drinking fluid for 18-23 weeks) inhibited the formation and decreased the size of both nonmalignant tumors and malignant tumors (Lou et al. 1999).

In cancer, p53 gene mutations are the most common genetic alterations observed, occurring in 50-60% of patients, including those with carcinomas and sarcomas. Caffeine has been shown to potentiate the destruction of p53 defective cells by inhibiting growth in the G2 phase. This ability of caffeine is important because the basis of many anticancer therapies is to damage tumor DNA and destroy the replicating cancer cells. Caffeine uncouples tumor cell-cycle progression by interfering with the replication and repair of DNA (Blasina et al. 1999; Ribeiro et al. 1999; Jiang et al. 2000; Valenzuela et al. 2000).


Theanine and Chemotherapy

L-theanine is a unique amino acid, naturally occurring in green tea, shown in one study to enhance Adriamycin concentration in tumors 2.7-fold and reduce tumor weight 62% over controls, whereas Adriamycin by itself did not reduce tumor weight (Sugiyama et al. 1998). Adriamycin is an anthracycline antibiotic having a wide spectrum of antitumor activity. Additionally, L-theanine was shown to reverse tumor resistance to certain chemotherapeutic drugs by forcing more of the drug to stay inside the tumor. It does not, however, increase the amount of drug in normal tissue, which sets it apart from other drugs designed to overcome multidrug resistance (Sadzuka et al. 2000a).


Theanine Makes Chemotherapy Work
In 1999 researchers performed a study testing the use of theanine in conjunction with a drug similar to doxorubicin known as idarubicin. The use of idarubicin has been tried in drug-resistant leukemia cells, but it caused toxic bone marrow suppression.

Researchers wanted to see if theanine would cause the drug idarubicin to work. In the first experiment, about one-fourth of the standard dose of idarubicin was used. At this dose, the drug usually does not work, and it also does not cause toxicity. When combined with theanine, however, idarubicin worked but still without toxicity. Tumor weight was reduced 49%, and the amount of drug in the tumors doubled. In the next experiment, theanine was added to the usual therapeutic dose of idarubicin. Theanine increased the effectiveness of idarubicin and significantly lessened usual bone marrow suppression. Leukocyte loss was reduced from 57% to 37% (Sadzuka et al. 2000c).

Part of theanine’s activity can be attributed to its mimicking of glutamate, an amino acid that potentiates glutathione. Theanine crowds out glutamate transport into tumor cells. Cancer cells (in confusion) erringly take in theanine, and theanine-created glutathione results. Glutathione (created by theanine) does not detoxify like natural glutathione, and instead blocks the ability of cancer cells to neutralize cancer-killing agents. Deprived of glutathione, cancer cells cannot remove chemotherapeutic agents, and the cell dies as a result of chemical poisoning (Sadzuka et al. 2001b).


SUMMARY

Chemotherapy drugs have a high rate of treatment failure. Twenty years of clinical trials using chemotherapy on advanced lung cancer patients yielded survival improvement of only 2 months. While new chemotherapy regimens appear to be improving survival, when these same regimens are tested on a wider range of cancer patients, the results have been disappointing. Oncologists at a single institution may obtain a 40-50% response rate in a tightly controlled study, but when these same chemotherapy drugs are administered in a real world setting, the response rates decline to only 17-27%.

New approaches beyond chemotherapy are required. There have been few clinical trials however, to determine if adjuvant approaches actually improve survival in cancer patients. In fairness, it should be pointed out that lymphomas (Hodgkin’s, non-Hodgkin’s, and Burkitt’s), myeloma, hairy cell leukemia, and chronic lymphocytic and certain other types of leukemia are all responding better to chemotherapy than 30 years ago. Also, depending on the timing of treatment, certain institutions are achieving better results with breast and early-stage lung cancers.

Our objective in conveying this large body of data is to provide chemotherapy patients with a better opportunity to beat cancer and minimize toxic side effects. We advocate that you follow a protocol based on a wide range of individual considerations, including the results of chemosensitivity and immunohistochemistry testing recommended at the beginning of this protocol. Information on your tumor cells obtained by these tests will help determine therapies most likely to work for you. In addition to these tumor cell tests, and based on your particular medical situation, you and your healthcare team will need to design a program specific to your needs and tolerances. The following is an outline of the steps described in this protocol:

  1. Decide on an appropriate chemotherapy regimen. Chemosensitivity and immunohistochemistry tumor cell tests can help you and your physician make a more informed decision.
  2. Be certain your physician understands the importance of guarding against hypoxia. This means keeping your hematocrit and hemoglobin in the upper ranges of normal. Since chemotherapy often induces anemia, the drug Procrit along with supplemental iron is often required.
  3. Based on tumor type, consider asking your physician to prescribe a COX-2 inhibiting drug, such as Lodine.
  4. Based on findings from the immunohistochemistry test, if your tumor expresses the K-Ras oncogene, consider high-dose statin drug therapy such as lovastatin (80 mg a day).
  5. The following supplements might help block growth signals used by cancer cells to escape eradication by chemotherapy. These supplements have also displayed antiangiogenesis properties. Some of these supplements may be best initiated 3 weeks after cessation of chemotherapy if one believes that antioxidants will protect cancer cells from the effects of chemotherapy drug(s):
    • Soy Extract (40% isoflavones), five 675-mg capsules taken 4 times a day. The only soy extract providing this high potency of soy isoflavones is a product called Ultra Soy. Note that isoflavones from soy have antioxidant properties.
    • Curcumin, 900 mg, with 5 mg of Bioperine (an alkaloid from Piper nigrum), 3 capsules 2-4 times a day taken two hours away from medications. Super Curcumin with Bioperine is a formulated product that contains this recommended dosage.
      Warning: Use caution when combining curcumin with other chemotherapy drugs. Do not take curcumin with the chemotherapy drugs Irinotecan, Camptosar, or CPT-11. Watch for NSAID-like side effects such as gastric ulceration because curcumin is a COX-2 inhibitor. Do not take curcumin if you have a biliary tract obstruction. Also note that curcumin is a potent antioxidant.
    • Green tea extract, two-three 725-mg capsules with meals.  Each capsule should be standardized to provide a minimum of 200 mg of epigallocatechin gallate (EGCG). It is the EGCG fraction of green tea that has shown the most active anticancer effects. These are available in a decaffeinated form for persons who are sensitive to caffeine or who want to take the less stimulating decaffeinated green tea extract capsules in the evening dose. Note that green tea is a potent antioxidant.
  6. To possibly enhance the efficacy of certain chemotherapy drugs:
    • Fish oil, 7-11 capsules of Super Omega-3 EPA/DHA w/Sesame Lignans & Olive Fruit Extract throughout the day.
    • L-theanine, five 100 mg capsules twice a day.
  7. The following natural supplements may reduce side effects and healthy tissue damage caused by chemotherapy. All of these supplements except shark liver oil are potent antioxidants:
    • Vitamin E, 400 IU a day of vitamin E succinate (dry powder natural vitamin E).
    • Vitamin C, 4000-12,000 mg throughout the day.
    • Coenzyme Q10, 200-300 mg daily in a softgel capsule for maximum absorption. (Refer to cautions about CoQ10 and chemotherapy.)
    • Melatonin, 3-50 mg at bedtime. Dose may be reduced after chemotherapy ends if too much morning drowsiness occurs. After several months, most cancer patients take 3-20 mg of melatonin at bedtime.
    • Se-methylselenocysteine (SeMSC), 200-400 mcg daily.
    • Whey protein concentrate isolate, 30-60 grams, in divided doses, daily.
      Note: Cancer patients undergoing chemotherapy should consider taking whey protein concentrate at least 10 days before beginning therapy and during therapy and then continuing with the whey protein for at least 30 days after completion of the therapy.
    • Shark liver oil, 200 mg alkyglycerols, 5 capsules daily for 30 days.
    • Digestive enzyme capsules may reduce the gas and bloating associated with high soy intake. Taking a 125-mg chewable tablet of Gas-X with each dose of soy might also be helpful.
  8. Ask your oncologist to consider prescribing immune-enhancing drugs suggested in this protocol, such as Leukine and alpha interferon or IL-2 (along with a retinoid drug).

For more information on specific types of cancer, see the following protocols: Breast Cancer, Cancer Radiation Therapy, Cancer Surgery, Colorectal Cancer, Leukemia/Lymphoma/Non-Hodgkin’s Lymphoma, Pancreatic Cancer, and Prostate Cancer. We suggest you check www.lefcancer.org regularly for the latest updates regarding cancer chemotherapy and related subjects.

Caution: There is continuing controversy concerning the use of antioxidant nutrients during conventional cancer therapy. Refer to the protocol entitled Cancer: Should Patients Take Dietary Supplements? for a discussion about whether cancer patients should take high doses of free-radical-suppressing nutrients during active therapy.

ADDITIONAL INFORMATION ON CANCER TREATMENT

After reading this protocol, please refer to Cancer Treatment: The Critical Factors. It contains important additional information for the chemotherapy patient that we do not want to duplicate in this protocol section. Cancer patients may want to refer to the other protocols in this edition or visit our website at www.lef.org or www.lefcancer.org.

FOR MORE INFORMATION

U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health National Cancer Institute, Bethesda, MD 20892 and NIH Publication No. 94-1136.

PRODUCT AVAILABILITY

Ultra Soy Extract; Super Curcumin with Bioperine; Mega Green Tea Extract; L-theanine; Super Absorbable CoQ10; melatonin; whey protein concentrate; vitamins A, C, D, and E succinate; Se-methylselenocysteine (SeMSC); Super Omega-3 EPA/DHA w/Sesame Lignans & Olive Fruit Extract, and Super Digestive Enzymes can be obtained by calling             (800) 544-4440 begin_of_the_skype_highlighting (800) 544-4440 end_of_the_skype_highlighting or by ordering online.

STAYING INFORMED

The information published in this protocol is only as current as the day the manuscript was sent to the printer. This protocol raises many issues that are subject to change as new data emerge. Furthermore, cancer is still a disease with unacceptably high mortality rates, and none of our suggested regimens can guarantee a cure.

The Life Extension Foundation is constantly uncovering information to provide to cancer patients. A special website has been established for the purpose of updating patients on new findings that directly pertain to the published cancer protocols. Whenever Life Extension discovers information that may benefit cancer patients, it will be posted on the website www.lefcancer.org.

Before utilizing this cancer protocol, we suggest that you check www.lefcancer.org to see if any substantive changes have been made to the recommendations described herein. Based on the sheer number of newly published findings, there could be significant alterations to the information you have just read.

image
*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.
The information provided on this site is for informational purposes only and is not intended as a substitute for advice from your physician or other health care professional or any information contained on or in any product label or packaging. You should not use the information on this site for diagnosis or treatment of any health problem or for prescription of any medication or other treatment. You should consult with a healthcare professional before starting any diet, exercise or supplementation program, before taking any medication, or if you have or suspect you might have a health problem. You should not stop taking any medication without first consulting your physician.
All Contents Copyright © 1995-2011 Life Extension Foundation All rights reserved. Life Extension

Antioxidants and Cancer: Quercetin

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Posted 19 Jun 2011 — by James Street
Category antioxidants, Complementary and Alternative Medicine, quercetin

 

Page 196 Alternative Medicine Review

Volume 5 Number 3 Ÿ 2000
Copyrightc2000 Thorne Research, Inc. All Rights Reserved.

Please visit the webpage location of this article for the original Adobe file

Antioxidants and Cancer III:
Quercetin
Davis W. Lamson, MS, ND, and Matthew S. Brignall, ND
Abstract
Quercetin is a flavonoid molecule ubiquitous in nature. A number of its actions make it
a potential anti-cancer agent, including cell cycle regulation, interaction with type II
estrogen binding sites, and tyrosine kinase inhibition. Quercetin appears to be associated
with little toxicity when administered orally or intravenously. Much in vitro and some
preliminary animal and human data indicate quercetin inhibits tumor growth. More
research is needed to elucidate the absorption of oral doses and the magnitude of the
anti-cancer effect.
(Altern Med Rev 2000;5(3):196-208)
Introduction
Quercetin (3,3f,4f,5,7-pentahydroxyflavone; Figure 1, R= OH) belongs to an extensive
class of polyphenolic flavonoid compounds almost ubiquitous in plants and plant food sources.
Frequently quercetin occurs as glycosides (sugar derivatives); e.g., rutin (Figure 1) in which the
hydrogen of the R-4 hydroxyl group is replaced by a disaccharide. Quercetin is termed the
aglycone, or sugarless form of rutin. Two extensive volumes, the proceedings of major meetings
on plant flavonoids, presented much of the biological and medical data about quercetin in
1985 and 1987.1,2
Quercetin is the major bioflavonoid in the human diet. The estimated average daily
dietary intake of quercetin by an individual in the United States is 25 mg.3 Its reputation as an
antioxidant stems from the reactivity of phenolic compounds with free radical species to form
phenoxy radicals which are considerably less reactive. Additionally, one can envision a polyphenolic
compound easily oxidizable to a quinoid form (similar to vitamin K) and participating in
the redox chemistry of nature.
In recent years, research about quercetin has ranged from considering it potentially
carcinogenic to examination of its promise as an anti-cancer agent. Four pressing questions
arise. Is additional dietary supplementation safe? Is quercetin absorbed and bioavailable when
given orally? Is it active against malignant human cells and could its use be developed? Are
additional routes such as intravenous or transdermal safe or more advantageous? It is the object
of this review to present evidence about these concerns and outline gaps in the available data
which need to be filled in order to determine whether quercetin has an appreciable role in future
cancer therapy.
Davis W. Lamson, MS, ND
Private practice, Tahoma Clinic- Kent, WA. Coordinator of Oncology, Bastyr University- Kenmore, WA. Correspondence Address: 9803 17th Ave. NE,
Seattle, WA. 98115. email: davisl@seanet.com
Matthew S. Brignall, ND
1999 graduate, Bastyr University. Currently doing a research fellowship at Tahoma Clinic in Kent, WA.
e-mail: mattandmolly@w-link.net
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
Antioxidants & Cancer: Quercetin
Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000 Page 197
Absorption of Quercetin
Most animal and human trials of oral
dosages of quercetin aglycone show absorption
in the vicinity of 20 percent. An early trial
in rabbits showed 25 percent of a 2-2.5 g oral
dose was accountable for in the urine.4 In light
of more recent findings of urinary excretion,
this is a questionable result.5 Rats eating a diet
supplemented with 0.2-percent quercetin for
three weeks attained a serum concentration of
133 microM, mainly in sulfated and
glucuronidated forms.6 Humans fed fried onions
containing quercetin glucosides equivalent
to 64 mg of the aglycone form reached a
maximum serum concentration of 196 ng/ml
(0.6 microM) 2.9 hours after ingestion. The
half-life of this dose was 16.8 hours, and significant
serum levels were noted up to 48 hours
post ingestion.7
Nine healthy ileostomy patients, chosen
to avoid colon flora breakdown of unabsorbed
material, were tested for absorption of
various forms of quercetin. They absorbed 24
} 9 percent of 100 mg pure aglycone, 17 } 15
percent of rutinoside, and 52 } 15 percent of
glucoside given mixed into a meal. Elimination
half-life was measured at 25 hours.8 These
findings were surprising in light of the fact that
most absorption was previously thought to
be exclusively as aglycone and to occur in
the large intestine.9 These findings were later
criticized on the ground that no screening
was done to rule out malabsorption in a
population assumed to have severe gastrointestinal
disease.10 The researchers defended
their model based on the normal serum
cholesterol concentrations and absorption
of PABA.8 The same investigators fed
nine healthy subjects quercetin glucosides
equivalent to 64 mg aglycone from onions,
glycosides equivalent to 100 mg aglycone
from apples, and pure rutinosides equivalent
to 100 mg aglycone. Peak plasma levels of
225 ng/ml (0.8 microM) were reached after
the onion meal, 90 ng/ml for the apples, and
80 ng/ml for the rutinoside. Half-life was
again found to be about 25 hours.11 Thus, it
can be determined that absorption of dietary
quercetin is reasonably generous. It has not
been determined whether pharmacologic doses
are absorbed proportionally.
Until recently, the absorption of oral
quercetin was thought to be poor. This was
based on a 1975 report that showed a 4-gram
oral dose of quercetin aglycone led to no measurable
quercetin in either the plasma or urine
of healthy volunteers.12 This report may be
flawed on the grounds that the serum assay
was only sensitive to 0.1 mcg/ml, a serum level
not much less than that found in other trials.
Also, urinary output was used as a primary
measure of absorption. Later trials have found
intact quercetin urinary excretion is negligible.
5,8
The serum quercetin concentrations
required for anti-cancer activity (upwards of
10 microM, see below) are much higher than
those achieved with oral doses in human studies.
Since a 100 mg single dose was found to
create a serum concentration of 0.8 microM
quercetin,11 one could extrapolate that a 1500
mg daily dose might attain a 10 microM level.
The relative long half-life of quercetin may
result in even higher serum concentrations.
Figure 1. Structure of Naturally Occurring
Flavonoids Showing Numbering of Ring Atoms
HO
R3 O
R4
R2
R1
O
In quercetin R1, R2, and R3 are all OH: rutin is a glycoside of quercetin
in which R4 is the disaccharide, rutinose (ƒÀ-1-L-rhamnosido-6-o-glucose).
From Rahman, A., et al., Carcinogenesis 1989;10:1833-1839.
Page 198 Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
Data from an animal study cited above suggest
that concentrations of quercetin above 10
microM are attainable with oral doses.6 A
single intravenous dose in humans of 100 mg
led to a serum quercetin concentration of 12
microM (4.1 mcg/ml).12
Safety of Quercetin
A single oral dose of up to four grams
of quercetin was not associated with side-effects
in humans.12 Single intravenous bolus
doses of 100 mg were apparently well tolerated
as well.12 Intravenous bolus of 1400 mg/
m2 (approximately 2.5 grams in a 70 kg adult)
once weekly for three weeks was associated
with renal toxicity in two of ten patients. The
two patients had a reduction in glomerular flow
rate of nearly 20 percent in the first 24 hours.
The reduction resolved within one week, and
this effect was not cumulative over subsequent
doses in the phase I trial in a population of
advanced cancer patients. In one patient, nephrotoxicity
was averted on subsequent doses by
administration of IV saline before and 5-percent
dextrose after quercetin. Transient flushing
and pain at the injection site were noted in
a dose-dependent manner. The 1400 mg/m2/
week dose was recommended for a phase II
trial.13
Quercetin has long been known to be
among the most mutagenic of the flavonoids.
This property has been demonstrated in the
Ames test,14 in cell culture,15 and in human
DNA.16 The urine and feces of rats given oral
or intraperitoneal doses of quercetin have been
found to have mutagenic activity, suggesting
this property may be important in vivo.17
Mutagenicity does not always imply
carcinogenicity, however. Most studies have
found quercetin to have no carcinogenic activity
in vivo. An early study found that rats
consuming diets containing up to 1-percent
quercetin (roughly 400 mg/kg) over 410 days
had no increase in gross pathology. Total body
weight, as well as organ weights were found
to be similar to control animals. No increased
risk of cancer was found in quercetin-treated
animals compared with controls.18 A later rat
study found diets containing as much as 10-
percent quercetin for 850 days caused no significant
change in body weight or increase in
tumor number or size compared with controls.
19 Administration of diets containing up
to 10-percent quercetin to golden hamsters for
735 days was also not found to lead to increased
tumor incidence compared to control
diets.20 Other similar studies have found a lack
of carcinogenicity of quercetin and its glycosides.
21-23
There are, however, studies that do
appear to show an increased risk of tumors
with quercetin administration. In a study by
Pamucu et al, albino Norwegian rats were fed
a diet supplemented with 0.1-percent quercetin
for 406 days. By the conclusion of the experiment,
80 percent of treated rats had developed
intestinal tumors and 20 percent had bladder
tumors. No tumors of either type were seen
in control animals. Mean survival times were
similar in treated and untreated animals.24 It is
yet unknown why these results are so vastly
different from other published trials. A possible
explanation is that the trials where quercetin
was not found to be carcinogenic had
control diets consisting of commercial pellets,
while the Pamukcu study used a grain based
control diet.20 Perhaps the finding of carcinogenicity
was specific to the strain of rats (Norwegian),
and cannot be generalized to other
species. A bimodal curve of carcinogenicity
is unlikely, as the trial by Ambrose et al found
no increased tumor incidence in rats fed 0.25
percent quercetin as well as higher doses.18As
yet, the meaning of the findings of Pamukcu
et al are not clear, and should be interpreted
cautiously.
The National Toxicology Program
(NTP) investigated the carcinogenicity of quercetin
by feeding F344/N rats diets consisting
of up to 4-percent (1900 mg/kg) quercetin for
728 days. An increase of renal tubular adenomas
was seen in males in the 4-percent
Antioxidants & Cancer: Quercetin
Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000 Page 199
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
quercetin group compared with controls (8/50
compared with 1/50). This increase was not
found in females.3 These data have been criticized
on the grounds that the increase in benign
tumors was only noted when additional
step sections were analyzed, making these
findings of unclear significance.25,26 The NTP
trial also found a dose-related decrease in
mammary fibroadenomas in treated animals
(9/50 in high-dose compared with 29/50 controls).
Other than the renal adenomas, no other
lesions were noted related to quercetin.3 At the
present time, quercetin is not classified by the
NTP report as a human carcinogen. It is also
unclear from the published report if the control
animals also underwent the additional stepsection
analysis.
Major Molecular Mechanisms of
Action
Down Regulation of Mutant P53
Protein
Quercetin (248 microM) was found to
down regulate expression of mutant p53 protein
to nearly undetectable levels in human
breast cancer cell lines. Lower concentrations
gave less reduction.27
The inhibition of expression
of p53 was
found to arrest the cells
in the G2-M phase of
the cell cycle. This
down regulation was
found to be much less
in cells with an intact
p53 gene.28 Mutations
of p53 are among the
most common genetic
abnormalities in human
cancers.29
G1 Phase Arrest
The G1 checkpoint
controlled by the
p53 gene is a major site for the control of cellular
proliferation. Quercetin has been found
to arrest human leukemic T-cells in the late
G1 phase of the cell cycle. At a 70 microM
concentration, 64 percent of cells were in G0/
G1 compared with 50 percent in control cultures.
30 This G1 arrest was also seen in gastric
cancer cells treated with quercetin. Concentrations
of 70 microM were found to reduce
DNA replication to 14 percent of control values,
leading to a delay of cell division. This
effect was reversible upon removal of quercetin
from the medium. At the 70 microM concentration,
quercetin was found to reduce
growth of cell cultures to 10 percent of that
seen in controls.31
Tyrosine Kinase Inhibition
Tyrosine kinases are a family of proteins
located in or near the cell membrane involved
in the transduction of growth factor signals
to the nucleus. In patients with advanced
cancers, intravenous administration of quercetin
(dosages 60-1700 mg/m2) led to inhibition
of lymphocyte tyrosine kinase at one hour
in nine of eleven cases. This inhibition was
seen as late as 16 hours post-administration.13
Figure 2. Cell Replication Cycle Showing Checkpoints Influenced
by Intact p53 and p21 Genes.
G2 Checkpoint Mitosis
G2 Phase
DNA Synthesis
G0
Resting
Phase
G1 Checkpoint
G1 Phase
Page 200 Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
In vitro experiments have confirmed these results,
both in non-malignant cells32 and in rat
mammary tumor cells.33 Tyrosine kinase expression
is thought to be involved in oncogenesis
via an ability to override normal regulatory
growth control.13,34 Drugs targeting tyrosine
kinase activity (tyrphostins) are envisioned
as possible antitumor agents without
the cytotoxic side-effects seen with conventional
chemotherapy.35 Quercetin was the first
tyrosine kinase inhibiting compound tested in
a human phase I trial.13
Estrogen Receptor Binding
Capacity
The role of the type II estrogen receptor
(ER II) in vivo is not entirely clear. Although
the ER II does bind estrogen in vitro,
the low affinity makes it likely these sites are
occupied by another ligand. One possible explanation
offered is that ER II sites are intended
for a flavonoid-like substance with growthinhibitory
capability.36 Quercetin has been
shown to induce ER II expression in both type
I estrogen receptor positive (ER+) and type I
Figure 3. Sites of Quercetin Interference in Pathways of Malignant Development (references
in parentheses; Q=quercetin).
1. Mutant p53 protein +HSP’s
(heat shock proteins)
Mutant p53 protein . HSP
Complex (results in failure
to arrest malignant cell
growth)
(27) (39, 40, 41)
Mutant p53 gene
expression
HS Protein synthesis
2. Tyrosine Kinase
cell surface protein
(13, 33)
Activation overrides growth control (34)
Q
3. Quercetin Induces expression
of estrogen receptor II
binding sites (ERII) (37)
Q binds to
ER II sites (38)
Q . ERII Complex
gives greater growth
inhibition of ER
negative cells (36, 38)
4. Mutant p21 ras
gene
Mutant p21 ras
protein
Mutant p21 ras
protein . GTP
complex (signals
Q (44) DNA replication) (45)
Q
Antioxidants & Cancer: Quercetin
Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000 Page 201
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
estrogen receptor negative (ER-) human breast
cancer cells. The induction of ER II allows for
greater growth inhibition of ER- cells with
quercetin treatment.37 In cultured human melanoma
cells, quercetin was found to bind ER II
sites with an affinity similar to tamoxifen and
diethylstilbestrol. The concentration required
for 50-percent growth inhibition for one cell
line was lower for quercetin (7 nM) than for
tamoxifen (9 nM), otherwise the growth inhibitory
activity of the two compounds was
similar.38 ER II sites are found in normal tissue
and on many different human tumor types,
including breast, ovarian, colorectal,
meningeal, leukemic, and melanoma.38 ER II
expression is independent of estrogen-receptor
(type I) status.
Inhibition of Heat Shock Proteins
Quercetin has been found to inhibit
production of heat shock proteins in several
malignant cell lines, including breast cancer,39
leukemia,40 and colon cancer.41 Heat shock proteins
form a complex with mutant p53, which
allows tumor cells to bypass normal mechanisms
of cell cycle arrest. Heat shock proteins
also allow for improved cancer cell survival
under different bodily stresses (low circulation,
fever, etc.), and are associated with shorter
disease free survival42 and chemotherapy drug
resistance43 in breast cancer.
Inhibition of Expression of Ras
Proteins
Quercetin (10 microM) has been found
to inhibit the expression of the p21-ras
oncogene in cultured colon cancer cell lines.44
Mutations in this important gene usually impair
cellular GTP-ase, which has the effect of
continual activation of the signal for DNA replication.
Mutations of ras proto-oncogenes are
found in over 50 percent of colon cancers, as
well as many other tumor types.45
In Vitro Studies of Quercetin
Table 1 summarizes the in vitro experiments
which have studied the malignant cell
culture growth inhibition of quercetin. Each
assay showed quercetin to significantly inhibit
growth. The quercetin concentration at which
tumor cell growth was inhibited by 50 percent
inhibitory concentration (IC50) ranged from
7 nM to just over 100 microM. Serum quercetin
concentrations of 12 microM have been
achieved in humans with single IV doses12 with
no associated side-effects, and up to 400
microM with little toxicity noted.13 Concentrations
of serum quercetin over 100 microM
have been attained with oral doses in animal
studies.6
Two of the assays shown in Table 1
compared the IC50 of quercetin with that of
tamoxifen.46,47 In both cases, the two compounds
had similar inhibitory concentrations,
which the authors believe reflected their nearly
identical affinity for type II estrogen binding
sites.
In Vivo Studies of Quercetin
As yet, there has only been one phase
I trial of quercetin in advanced cancer patients
who were no longer responsive to
chemotherapy. The dose escalation and
adverse events seen in this trial were discussed
above in the toxicity section. Although none
of the treated patients met the World Health
Organization definition of tumor response
(partial response: 50-percent reduction in
tumor mass for greater than 30 days), two of
11 patients did have positive results. One
hepatocellular carcinoma patient had a
sustained (150 days) fall in serum alphafetoprotein
and alkaline phosphatase during
and after four low-dose, intravenous quercetin
treatments (60mg/m2) on a 3-week schedule.
A patient with stage four ovarian cancer who
had not responded to six courses of
cyclophosphamide/cisplatin chemotherapy
had a fall in the CA125 tumor marker from
Page 202 Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
290 to 55 units/ml following two treatments
of intravenous quercetin (420 mg/m2) three
weeks apart. She was continued on this
treatment, with less frequent administration
and the addition of carboplatin for six months.
There was continued suppression of the tumor
marker with no mention of tumor size. No data
were reported from the other patients.
Intravenous quercetin was found to inhibit
lymphocyte tyrosine kinase in nine of 11
patients assayed. As is usual in a phase I trial,
the focus of the authors was on
pharmacokinetics and toxicity, rather than
tumor outcome.13
Two animal studies have looked at the
anti-tumor properties of quercetin. In one
study, mice were inoculated with ascites tumor
cells and then treated intraperitoneally with
either quercetin or its glycoside, rutin. Animals
treated daily with 40 mg/kg quercetin had a
20-percent increase in life span, while those
treated with 160 mg/kg rutin had a 50-percent
increase in life span. If the rutin treatment was
split into two 80 mg/kg treatments per day, the
increase in life span became 94 percent.60
These in vivo results are interesting since in
vitro work showed rutin to have little effect
compared to quercetin on tumor tissue.54,57
Another animal study looked at the
effect of quercetin on mice bearing abdominal
tumors derived from a human pharyngeal
squamous cell carcinoma line. The mice were
given a daily intraperitoneal injection of
quercetin. All doses tested (20-, 200-, 400-,
Table 1. In Vivo Studies of Quercetin.
Bladder
Breast (MDA-MB-435)
Breast (MDA-MB-468)
Breast (MDA-MB-435)
Breast (MCF-7)
Breast (MCF-7)
Colon (HT29 and Caco-2)
Colon (HT29 and Caco-2)
Gastric (HGC-27, NUGC-2, MKN-7, and MKN-28)
Head and neck (HTB43)
Head and neck (HTB43 and CCL135)
Leukemia (14 AML lines and four ALL lines)
Leukemia (CML line K562)
Lung (non-small-cell lines)
Melanoma (MNT1, M10, M14)
Ovarian (OVCA 433)
Not given
55microM, LC50=26 microM
21 microM
31 microM
4.9 microM
15 microM
45-50 microM
30-40 microM
32-55 microM
Significant inhibition above
100 microM
Significant inhibition above
100 microM
Average IC50=2 microM
59 microM
0.45-2.28 microM
7nM, 20nM, 1-10 microM
10 microM
48
49
27
50
51
52
53
54
31
55
56
57
58
46
47
59
Malignant cell line IC50 Reference
Note: LD50=Dose lethal to 50% of cultured cells.
Antioxidants & Cancer: Quercetin
Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000 Page 203
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
and 800 mg/kg) demonstrated significant
inhibition of tumor growth. The 20 mg/kg dose
had an effect only slightly less than that seen
with 800 mg/kg. The effect on the growth of
normal human fibroblast cells was minimal.
The authors concluded that quercetin appears
to be a selective inhibitor of tumor cell
growth.56
Use of Quercetin with Standard
Oncologic Therapeutics
Radiotherapy
An in vitro study showed a significant
but mild enhancement of the cytotoxic effect
of radiation on rat hepatoma cells when quercetin
was added to the medium.61 A human
study showed topical and oral administration
of quercetin to reduce skin damage during radiotherapy
in patients with head and neck cancers.
62
Chemotherapy
Quercetin has been shown to increase
the therapeutic efficacy of cisplatin both in vivo
and in vitro. In mice bearing human tumor
xenografts, intraperitoneal treatment with a
combination of 20 mg/kg quercetin and 3 mg/
kg cisplatin led to a significantly reduced tumor
growth compared to treatment with either
drug alone.63 In contrast to the experiment using
various doses of quercetin on pharyngeal
cancer xenografts in mice discussed above,56
treatment with 20 mg/kg quercetin was not
found to be an effective single agent therapy.
An in vitro study using human ovarian and
endometrial cancer cell lines found that addition
of 0.01 to 10 microM quercetin to cisplatin
caused 1.5- to 30-fold potentiation of the cytotoxic
effect of cisplatin. An absence of potentiation
of the effect of adriamycin or
etoposide due to quercetin administration was
noted.64 Quercetin (10-100 microM) has also
been shown in vitro to protect normal renal
tubular cells from cisplatin toxicity.65
An in vitro study showed quercetin
worked synergistically with busulphan against
human leukemia cell lines. Quercetin/
busulphan concentrations in 1:1 and 3:1 ratios
led to demonstration of much smaller cytotoxic
doses of busulphan.58 Addition of 1-
10 microM quercetin to adriamycin treatment
led to a dose-dependent increase in cytotoxicity
compared with chemotherapy treatment
alone in cultured multidrug-resistant human
breast cancer cell lines.66 Quercetin has also
been shown in vitro to increase the cytotoxic
effect of cyclophosphamide,67 and to decrease
resistance to gemcitabine and topotecan.68
These last findings are consistent with the fact
that many flavonoids have been shown to decrease
resistance to chemotherapy in
multidrug-resistant tumor cell lines. The
mechanism of this action is unclear.
Future Research Directions
At the present time there are considerable
in vitro data that support the concept of
quercetin as an anti-cancer compound. These
promising data have not been followed up with
extensive human or animal research. This has
left a number of knowledge gaps regarding the
use of quercetin as a cancer treatment. These
gaps can best be demonstrated by returning to
the questions posed in the introduction.
Is Dietary Supplementation of
Quercetin Safe?
Human studies have not shown any
adverse effects associated with oral administration
of quercetin in a single dose of up to
four grams12 or after one month of 500 mg
twice daily.69 If quercetin is administered by
the intravenous route, it is advised to check
kidney function on a regular basis. The question
of carcinogenicity of quercetin still merits
further exploration, but most data suggest
increased cancer risk is not likely associated
with oral doses of quercetin.
Page 204 Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
Is Quercetin Absorbed and
Bioavailable When Given Orally?
The absorption studies cited above suggest
dietary quercetin is indeed readily taken
up in the human intestine. There are many
questions here, however. One is whether pharmacological
doses are absorbed in the same
percentage as dietary concentrations (roughly
20%). A recent experiment demonstrating
quercetin to be an effective agent for prostatitis
suggests enough quercetin is absorbed from
oral megadoses (500 mg twice daily) to have
a biological effect,69 but this has yet to be confirmed
in a cancer situation. Another question
concerns whether tissue concentrations of
quercetin mirror those found in the bloodstream.
At least one study has found free serum
quercetin to be less than one percent of
the total pool, indicating that it is tightly bound
to albumin in vivo. These authors hypothesized
that very little quercetin is available at the tissue
level.70 A third question concerns whether
the conjugated forms of quercetin making up
most of the circulating pool6 have similar anticancer
properties to the aglycone used in most
experiments.
Is It Active Against Malignant
Human Cells and Could Its Use Be
Developed?
Although the in vitro evidence is very
strong in this regard, there are cautions. As
discussed in the previous paragraph, it is currently
unknown if the forms of quercetin most
common in human serum (sulfated and
glucuronidated) have similar activities to the
aglycone. The major question remains whether
in vitro research is an accurate model for in
vivo systems.
Whether quercetin has any advantageous
or detrimental effects on immune function
in cancer is an important concern. Quercetin
has a history of use by nutritional physicians
as an anti-inflammatory and anti-allergy
agent.10 This action is thought to be largely
due to the inhibition of lipoxygenase and
cyclooxygenase, leading to a reduced production
of eicosanoid inflammatory mediators.
Quercetin is thought to inhibit cyclooxygenase
more potently than lipooxygenase.71 Inhibitors
of cyclooxygenase (NSAIDS) are currently
under research as potential chemotherapeutic
agents, particularly for colon cancer.72
Cyclooxygenase is known to be elevated in
certain epithelial tumors,73 and is thought to
be involved in angiogenesis.74
Certain drugs known to decrease
eicosanoid production are also known to decrease
immune function (e.g., prednisone).
Quercetin has been shown in vitro to significantly
reduce natural killer cell cytotoxicity
at 1 mM, and non-significantly to concentrations
as low as 1×10-11 M.75 However, when
rats were fed 100 mg/kg quercetin for seven
weeks, they were found to have increased natural
killer cell activity compared to those fed
placebo.75 So there appears either an in vitro/
in vivo confliction of effect or a biphasic concentration
effect. Since the quercetin dose associated
with increased immune function is
much higher than that usually used in humans,
the applicability of this study is questionable.
Are Additional Routes Such as
Intravenous or Transdermal Safe or
More Advantageous?
Since quercetin is quickly metabolized
in the liver, it is very possible that the best
means of administration could be those that
avoid the first-pass effect. The pilot trial of
intravenous dosage gave promising results, and
merits follow-up in a larger population.
Transdermal use of quercetin has not been
explored in humans to date.
Conclusion
In vitro research has shown quercetin
to have a number of separate and independent
mechanisms of anti-tumor action. Preliminary
animal and human studies have confirmed that
Antioxidants & Cancer: Quercetin
Alternative Medicine Review Ÿ Volume 5, Number 3 Ÿ 2000 Page 205
Copyrightc2000 Thorne Research, Inc. All Rights Reserved. No Reprint Without Written Permission
quercetin does indeed have therapeutic activity
in at least some cancer situations. Quercetin
has not shown any interference with chemotherapeutic
agents to the extent to which it
has been studied. Further research will be required
to outline the types of malignancy most
likely to benefit from this relatively non-toxic
therapy. Presently, the oral use of quercetin
appears safe and possibly useful in cancer patients.
For more information on antioxidants
and cancer, refer to Altern Med Rev
1999;4(5):304-329 and Altern Med Rev
2000;5(2):152-163.
The authors wish to thank Richard
Russell and the Smiling Dog Foundation for
financial support of this project and to Bastyr
University for its administration.
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Prevention of cytotoxic drug induced skin ulcers with dimethyl sulfoxide (DMSO) and α-tocopherole

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Posted 17 Jun 2011 — by James Street
Category alpha tocopherol, antioxidants, Chemotherapy, DMSO, Lung Cancer



Christian U. LudwidCorresponding Author Contact Information, a, Hans-Rudolf Stolla, Reto Obristla and Jean-Paul Obrechta

aDivision of Oncology, Department of Internal Medicine of the University, Kantonsspital, Basel, Switzerland

Accepted 11 September 1986.
Available online 12 May 2004.

 

Abstract

Accidental subcutaneous extravasation of several antineoplastic agents may provoke skin ulcerations for which there has been no simple and effective treatment. Since January 1983 we have treated all patients in our institution sustaining extravasation by a cytotoxic drug with a combination of DMSO and α-Tocopherole. During the first 48 hr after extravasation a mixture of 10% α-Tocopherole acetate and 90% DMSO was topically applied. The bandage was changed every 12 hr. So far eight patients with extravasation of an anthracycline or Mitomycin were treated on this protocol. No skin ulceration, functional or neurovascular impairment occured in any of these patients. The only toxic effect observed by this treatment was a minor skin irritation. The combination of DMSO and α-Tocopherole seems to prevent skin ulceration induced by anthracyclines and Mitomycin.

star, openPresented in Part at the IV World Conference on Lung Cancer, 25–30 August 1985, Toronto, Canada.

Alpha Lipoic Acid and Frataxin: A New Indication for an Old Antioxidant?

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Posted 15 Jun 2011 — by James Street
Category Alpha Lipoic Acid, Alpha Lipoic Acid, antioxidants, Chemotherapy, Cisplatin, docetaxel, Drug Resistance
Alpha Lipoic Acid and Frataxin: A New Indication for an Old Antioxidant?
James W. Russell
James W. Russell, Department of Neurology, University of Maryland School of Medicine & Maryland VA Medical Center, Baltimore, MD 21201, USA;

Correspondence: James W. Russell, M.D., M.S., Department of Neurology, University of Maryland, School of Medicine, 22 South Greene Street, Box 175, Baltimore, MD 21201-1595, Tel:             410-706-6689 begin_of_the_skype_highlighting 410-706-6689 end_of_the_skype_highlighting ; Fax: 410-706-4949 begin_of_the_skype_highlighting 410-706-4949 end_of_the_skype_highlighting, E-mail: JRussell@som.umaryland.edu

Cisplatin is an effective treatment for breast, ovarian, testicular, and small cell lung malignancies, however its use leads to a dose-limiting and cumulative sensory neuronopathy. The effects of cisplatin neurotoxicity can persist for decades (Strumberg et al., 2002). The mechanism of cisplatin toxicity is uncertain, although it has been shown in vitro to reduce fast axonal transport, and induces apoptosis in dorsal root ganglion cells (DRG) by forming high affinity adducts between cisplatin and either genomic or mitochondrial DNA (McDonald et al., 2005; Peltier and Russell 2002). Adduct formation is associated with translocation of the proapoptotic protein Bax to the mitochondrion and release of cytochrome c into the cytosol. This series of events leads to a fas receptor-independent form of programmed cell death (McDonald and Windebank 2002). Cisplatin is frequently administered in combination with paclitaxel and the effect of combination therapy has recently been tested in an animal model (Carozzi et al., 2009). Current data are insufficient to conclude if any tested neuroprotective agents, for example amifostine, diethyldithiocarbamate, glutathione, Org 2766, or Vitamin E prevent or reduce the neurotoxicity of platin drugs (Albers et al., 2007).

Dr. Melli and colleagues in “Alpha-lipoic Acid Prevents Mitochondrial Damage and Neurotoxicity in Experimental Chemotherapy Neuropathy” present an intriguing new mechanism for cisplatin neuronal injury. Using an embryonic day (E-15) DRG culture system, neurons exposed to cisplatin showed a significant reduction in frataxin expression (Melli et al., 2008). Human frataxin is a ~17kDa protein whose deficiency has been associated with Friedreich’s ataxia. Friedreich’s ataxia is a progressive neurodegenerative disease that affects both central and peripheral axons. However, like cisplatin neuropathy, Friedreich’s ataxia is associated with significant degeneration of DRG sensory neurons. Frataxin is intimately associated with several aspects of intracellular iron metabolism and detoxification including iron binding/storage and iron chaperone activity (Campanella et al., 2009). Frataxin also interacts with the electron transport chain proteins, activates glutathione peroxidase, and increases the mitochondrial membrane potential. Frataxin deficiency is associated with a severe deficiency in mitochondrial DNA, an event that results in reduced oxidative phosphorylation and altered antioxidant defenses. Furthermore, a major consequence of the severe depletion of mitochondrial DNA would be mitochondrial bioenergetic failure in the peripheral nervous system (Koch and Britton 2008).
Another observation in the present study is the formation of autophagosomes in DRG treated with cisplatin. Typical double membrane bound vacuoles containing degenerative mitochondria were observed in DRG neurons. Autophagy is an important process involved in the degradation of cytoplasmic organelles and in particular mitochondria. Recent research shows that autophagosomes form on the surface of the mitochondria and they then peel off from mitochondria. Autophagic programmed cell death (type II) is characterized by the accumulation of autophagic vesicles (autophagosomes and autophagolysosomes) and is often observed when massive cell elimination is demanded or when phagocytes do not have easy access to the dying cells (Shintani and Klionsky 2004). It is unclear if autophagy causes neuronal or axonal pathology or is a result of the injury. However despite this uncertainty, the current observations by Melli and colleagues provide a rational explanation for the pathophysiological changes that occur in cisplatin neuropathy.
In the present study, paclitaxel reduced the number of functioning mitochondria in DRG neurons and Schwann cells, induced apoptosis in both cells, and impaired neurite growth. Paclitaxel is a common adjunctive therapy in women with node positive breast cancer. It is frequently used in combination with cisplatin and other chemotherapeutic drugs and is also used for other solid tumors such as ovarian and non-small cell lung cancer. A length-dependent sensorimotor axonal neuropathy is a common dose-dependent side effect of treatment. It can also rarely cause cranial neuropathies, motor involvement and autonomic dysfunction (Peltier and Russell 2006). Paclitaxel binds to tubulin and hyperstabilizes microtubules thus promoting the assembly and reducing the disassembly of microtubules in unmyelinated and myelinated axons. These changes reduce normal axonal transport. Several potential therapies have been assessed in taxol-induced neuropathy including glutamine and calpain inhibitors (Peltier and Russell 2006). However, these potential neuroprotective therapies have not been tested in large randomized clinical trials.
An important observation in the study by Melli et al is the finding that alpha-lipoic acid (α-lipoic acid) prevented mitochondrial damage and that this was dependent on expression of frataxin. α-lipoic acid had neuroprotective effects with both cisplatin and paclitaxel toxicity in cell culture. In contrast to the data with cisplatin, the effect of α-lipoic acid on paclitaxel induced apoptosis was less significant, which is not surprising as apoptosis is not the main toxic mechanism of paclitaxel. In DRG cultures transfected with anti-frataxin siRNA, there was reduced axonal outgrowth. Cisplatin and paclitaxel showed increased neurotoxicity in frataxin knockdown cultures and α-lipoic acid did not prevent the axonal damage as it did in non-transfected cultures. In contrast, α-lipoic acid increased the expression of frataxin in sensory neurons. A further observation was that whereas cisplatin significantly reduces the expression of frataxin, paclitaxel does not. This is despite an increased neurotoxicity in the anti-frataxin siRNA cultures. The implication of this is not clear. Importantly, the α-lipoic acid had to be administered prior to exposure to cisplatin or paclitaxel in order to prevent neurotoxicity. It should be clearly noted that these are cell culture studies and may not be clinically relevant. However, α-lipoic acid has been shown in a small study to improve neuropathy when used post docetaxel/cisplatin treatment in subjects who had already developed peripheral neuropathy (Gedlicka et al., 2003). Patients were treated with 600 mg intravenous α-lipoic acid once a week for 3–5 weeks followed by 1800 mg orally daily for up to 6 months. These results will need to be confirmed in a larger randomized controlled study.
α-lipoic acid is one of the most extensively studied antioxidants. Oxidative stress has been associated with several types of neuropathy including diabetic and chemotherapy-induced neuropathy (Russell and Kaminsky 2005). In the peripheral nerve, α-lipoic acid reduces oxidative stress and the generation of peroxinitrites, inhibits activation of caspases, and improves peripheral nerve endoneurial blood flow. α-lipoic acid in vivo is reduced to active dihydrolipoate and is able to regenerate other antioxidants such as vitamin C, vitamin E, and reduced glutathione through redox cycling. The antioxidant potential of α-lipoic acid has been used to treat several neurological diseases including multiple sclerosis and stroke. However, it has been used most extensively for the treatment of neuropathy, and in particular in diabetic neuropathy. Most experimental diabetic neuropathy studies have shown variable degrees of improvement with α-lipoic acid treatment. Clinical trials have shown mixed results. However, in one of the larger, multicenter, randomized, double-blind, placebo-controlled studies of diabetic neuropathy, there was a small but significant improvement in the neuropathy symptom score but not in other endpoint measures (Ziegler et al., 1999). In general, short term treatment with α-lipoic acid mildly improves both neuropathic symptoms and deficits and the treatment has relatively few side effects.
The observation that α-lipoic acid prevents neuronal and Schwann cell injury in an experimental cell culture model of cisplatin and paclitaxel-induced toxicity and that this is dependent on levels of frataxin, is a novel finding. It remains to be seen whether these observations will prove to be true in toxic neuropathy in humans and if α-lipoic acid will prevent this neurotoxicity. Further basic science studies to examine alternative mechanism/s of action of α-lipoic acid in chemotherapy-induced neuropathy and more robust clinical trials with α-lipoic acid are needed.
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Neuroprotection During Chemotherapy: A Systematic Review

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Posted 15 Jun 2011 — by James Street
Category antioxidants, Chemotherapy, Neuropathy

Walker, Melanie MD*; Ni, Oliver MD†

Abstract

The development of neurotoxicity during antineoplastic therapy is one of the most common reasons for termination or modification of cancer treatment. A number of different agents have been proposed to provide neuroprotection without affecting antitumor efficacy. This review provides an evidence-based summary of neuroprotective medicines, an overview of the literature relating to neuroprotection during cancer treatment and a Neurologist perspective risk assessment and management. Through a systematic review the authors identified 49 papers published to date that report human clinical trials involving potential neuroprotectants in adults. Case reports and series completed in a prospective fashion were also included. Sensory neuropathies were the most prevalent subtype in the literature, and most were at least partially reversible with or without neuroprotective treatment. The majority of study medications had minimal side effects, though 2 trials were prematurely terminated because of adverse patient outcomes. No study reported an effect on antitumor efficacy. Because of the variability in study design, cancer type, outcome measures, and clinical confirmation of neuropathy, meta-analysis could not be appropriately performed. We highlight risk factors and discuss neuropathy screening. Descriptive analysis is provided which reveals that many of the agents studied were likely to confer some at least some neuroprotective benefit.

American Journal of Clinical Oncology:
February 2007 – Volume 30 – Issue 1 – pp 82-92
doi: 10.1097/01.coc.0000239135.90175.4f
Review Article

Cancer Chemotherapy and Antioxidants

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Posted 09 Jun 2011 — by James Street
Category antioxidants, Chemotherapy
Supplement: Free Radicals: The Pros and Cons of Antioxidants

Cancer Chemotherapy and Antioxidants1

Kenneth A. Conklin2

Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA 90095-1778

2To whom correspondence should be addressed. E-mail: kconklin@mednet.ucla.edu.

KEY WORDS: • antioxidants • caspase • chemotherapy • cisplatin • coenzyme Q10 • death receptor • doxorubicin

EXPANDED ABSTRACT

Does the administration of antioxidants during cancer chemotherapy affect antineoplastic efficacy or the development of side effects? Although the majority of preclinical studies involving the use of in vitro systems and animal models support the contention that certain antioxidants are of benefit, few clinical studies have been done (1,2). Factors to consider in the design of studies to answer the question posed above include the properties of the individual antioxidants, the mechanism of action of the antineoplastic agents, and the mechanism whereby antineoplastic agents cause their side effects. Additionally, the impact of chemotherapy-induced oxidative stress upon antineoplastic efficacy and the role that reactive oxygen species (ROS)3 may play in drug-induced apoptosis need to be elucidated.

All antioxidants cannot be viewed as equal when evaluating their potential impact on cancer chemotherapy, and an individual antioxidant cannot be anticipated to have the same impact on the activity of all cancer chemotherapeutic agents. Small molecular weight antioxidant molecules are effective reducing agents but some, including glutathione (GSH), N-acetyl cysteine (NAC), and alpha-lipoic acid, also are strong nucleophiles because they possess a sulfhydryl group. While all antioxidants are capable of detoxifying free radicals, those that possess strong nucleophilic properties can bind and inactivate the electrophilic intermediates of antineoplastic agents that act via nucleophilic substitution reactions, i.e., platinum-coordination complexes and most alkylating agents. Competition between nucleophilic antioxidants and the nucleophilic cellular targets of these anticancer agents can reduce the efficacy of the therapy. Selenium also can be considered a nucleophilic antioxidant. Although inorganic selenium does not function as an antioxidant, it is incorporated into selenoproteins (as selenocysteine or selenomethionine) and other selenium compounds such as methylselenol. Because selenium possesses properties similar to sulfur, selenoproteins and organoselenols have nucleophilic properties. Additionally, selenium induces the synthesis of the cysteine-rich metallothioneins, which can bind to electrophilic intermediates of platinum-coordination complexes and alkylating agents, and elevated levels of methallothioneins are associated with resistance to these antineoplastic agents (3).

If generation of ROS by a cancer chemotherapeutic agent or a free radical intermediate of the drug plays a role in its cytotoxicity, antioxidants may interfere with the drug’s antineoplastic activity. However, if the reactive species are responsible only for the drug’s adverse effects, antioxidants may actually reduce the severity of such effects without interfering with the drug’s antineoplastic activity. Thus, it is important to distinguish between a drug’s ability to induce oxidative stress in biological systems and the role, if any, that ROS or free radical intermediates play in the mechanism of action of the drug.

The drugs of many classes of antineoplastic agents are known to generate a high level of oxidative stress in biological systems (1). These classes of drugs include the anthracyclines, most alkylating agents, platinum-coordination complexes, epipodophyllotoxins, and camptothecins. For these drugs, the hepatic microsomal monooxygenase system is a primary site where ROS are generated, although other enzymatic (e.g., xanthine oxidase) and nonenzymatic (Fenton and Haber-Weiss reactions) mechanisms also play a role. The electron transport system of cardiac mitochondria is another site where significant levels of ROS are generated by anthracyclines (4). Although some classes of antineoplastic agents generate high levels of oxidative stress, others, including the taxanes, vinca alkaloids, antifolates, and nucleoside and nucleotide analogues, generate only low levels. Nevertheless, all drugs generate some free radicals as they induce apoptosis in cancer cells.

One of the primary pathways of drug-induced apoptosis is the pathway that involves release of cytochrome c from mitochondria (5). When cytochrome c is displaced from the electron transport chain, instead of electrons being transferred to oxygen via cytochrome c oxidase with the formation of water, electrons are diverted from NADH dehydrogenase (Complex I) and reduced coenzyme Q10 to oxygen with the concomitant formation of superoxide radicals. Although superoxide is not highly toxic, mitochondrial superoxide dismutase generates hydrogen peroxide from superoxide and, in the presence of reduced iron that is abundant in mitochondria, highly toxic hydroxyl radicals are formed via Fenton and Haber-Weiss reactions. Thus, all drugs that induce apoptosis by this mechanism generate some degree of oxidative stress, although this does not imply that free radical generation is necessary for a drug to exert its cytotoxic effect on neoplastic cells, because the apoptotic process is initiated by cytochrome c release and superoxide generation occurs secondarily.

The mechanism of action of only a few antineoplastic agents has been definitively linked to a free radical intermediate of the parent drug. Examples of antineoplastic agents that have been so linked include mitomycin-C, which creates DNA interstrand crosslinks following reduction of its aziridine ring, and bleomycin, which cleaves DNA by hydrogen abstraction by its iron-binding arm, which functions as a ferrous oxidase. Most of the other major classes of antineoplastic agents have well-established mechanisms of action that are independent of free radical intermediates or free radical generation. These include the antifolates and nucleoside and nucleotide analogues that impact DNA synthesis, the vinca alkaloids and taxanes that interfere with microtubule function, the epipodophyllotoxins (etoposide, teniposide) that interfere with topoisomerase II activity, and the camptothecins (topotecan, irinotecan) that interfere with topoisomerase I activity.

The platinum coordination complexes (cisplatin, carboplatin, oxaliplatin) and most alkylating agents form strong electrophilic intermediates that act via nucleophilic substitution reactions to form inter- and intrastrand DNA crosslinks. Although toxicity among these agents varies, most side effects also are attributed to nucleophilic substitution reactions, e.g., cisplatin toxicity (nephrotoxicity, neurotoxicity, ototoxicity) is attributable to protein sulfhydryl binding and inactivation of thiol-containing enzymes. Antioxidants that act as reducing agents do not appear to interfere with the antineoplastic activity of these agents nor do they prevent the development of side effects (1), which suggests that free radical generation does not play a role in the antineoplastic activity or the toxicity of these agents. In contrast to antioxidants that act as reducing agents, nucleophiles, such as GSH, NAC, and thiosulfate, can bond covalently to electrophilic compounds such as cisplatin, and mixing cisplatin with thiosulfate prior to administration blocks the antineoplastic agent’s activity (1). However, several animal and clinical studies have shown that intravenous administration of GSH shortly before administration of cisplatin reduces the drug’s toxicity without reducing its anticancer activity (1). This may be explained by the high renal and neural intracellular levels of γ-glutamyl transpeptidase (GGT), an enzyme that hydrolyzes circulating GSH (GluCysGly) to Glu and CysGly and transports these products into the cell (6). The high enzyme levels in normal tissues allow for rapid clearing of circulating GSH, thus preventing cisplatin binding to GSH in the bloodstream, and also results in high GSH levels in renal and neural tissue, thus protecting them from cisplatin toxicity. Renal cells also have unique mechanisms for concentrating selenium and for formation of methylselenol and glutathionylselenol, compounds that also protect the kidneys from cisplatin toxicity (7). Most cancer cells have low levels of GGT. Thus, intravenous administration of GSH does not increase the GSH content of most cancer cells that could reduce the antineoplastic activity of cisplatin. However, GTT may be expressed in higher amounts or be inducible in some neoplastic cells (8). The potential selective protection of normal tissues from cisplatin toxicity warrants further investigation.

Several mechanisms have been proposed for the anticancer activity of anthracyclines. Although the most studied anthracycline, doxorubicin, alters membrane function, signal transduction such as pathways involving protein kinase C, and many other cellular functions, the most compelling evidence for its primary mechanism of action is via intercalation with double-stranded DNA and inhibition of topoisomerase II activity. This effect is evident at clinically relevant concentrations, with the drug being localized primarily in the nucleus of neoplastic cells and acting in the S-phase of the cell cycle. This supports topoisomerase II inhibition as the drug’s primary cytotoxic mechanism. However, doxorubicin readily undergoes a one-electron reduction to its semiquinone, which can donate an electron to molecular oxygen resulting in superoxide generation. Although generation of hydroxyl radicals from superoxide is an attractive explanation for the cytotoxicity of doxorubicin, several lines of evidence suggest that this mechanism does not contribute significantly to the drug’s anticancer activity: (a) doxorubicin is localized primarily in the nucleus of neoplastic cells, and DNA-intercalated doxorubicin is not readily reduced; (b) although semiquinone formation can occur in membranes, including the nuclear membrane and the sarcoplasmic reticulum, the hepatic microsomal cytochrome P450 monooxygenase system and mitochondria of cardiac cells are the primary sites where high levels of the semiquinone are generated; (c) preclinical studies show that antioxidants reduce doxorubicin-induced oxidative stress while preserving the drug’s antineoplastic activity (1,2); (d) several clinical studies suggest that antioxidants such as coenzyme Q10 do not interfere with the drug’s anticancer efficacy (1,2); (e) most studies that have shown doxorubicin-induced hydroxyl radical formation to be cytotoxic have used concentrations (several micromolar) that are far above those that are clinically relevant (a 60 mg/m2 bolus dose results in a peak level of 1 micromolar doxorubicin, which rapidly declines to a level of ∼10 nanomolar, which is sustained for a period of up to 1 wk); (f) doxorubicin has been shown to be cytotoxic under hypoxic conditions; and (g) many neoplastic cells are not sensitized to doxorubicin by depletion of antioxidants.

Although free radical generation may not play a significant role in the antineoplastic activity of doxorubicin, there is compelling evidence that disruption of the electron transport system and hydroxyl radical generation in mitochondria of cardiac cells accounts for the drug’s acute and chronic cardiotoxicity. The selective toxicity of doxorubicin to cardiac cells is accounted for by the unique structure of the cardiac mitochondrial inner membrane, which possesses a cytosolic (outer surface, or intermembranous) NADH dehydrogenase in addition to the matrix (inner surface) NADH dehydrogenase that is present in the mitochondria of all cells (9). Doxorubicin (a tetracycline ring with a sugar moiety) is hydrophilic and cannot penetrate the inner membrane and be reduced by the matrix enzyme. However, in cardiac mitochondria, doxorubicin, which can penetrate the outer membrane and enter the mitochondrial cytosol, is reduced by the cytosolic NADH dehydrogenase to its semiquinone. Intramolecular rearrangement results in formation of the lipophilic deoxyaglycone of doxorubicin that penetrates the inner membrane where it then inhibits coenzyme Q10-dependent enzymes, accounting for disruption of mitochondrial energetics and resulting in the development of acute cardiotoxicity (arrhythmias and reduced ejection fraction). The deoxyaglycone also competes with coenzyme Q10 (both structurally are quinones) as an electron acceptor, diverting electrons to molecular oxygen with the formation of superoxide radicals, and displaces coenzyme Q10 from the electron transport chain, resulting in elevated plasma levels of coenzyme Q10 (10). These effects explain the generation of elevated levels of ROS in cardiac cells that lasts for several weeks following administration of doxorubicin and the high levels of mitochondrial DNA adducts that form in heart mitochondria and result in suppression of mitochondrial gene expression for critical components of the electron transport system (11), such as coenzyme Q10 (12). These long-lasting effects most likely explain mitochondrial disruption, the first cytological evidence of chronic cardiotoxicity (13,14), which leads to myocyte degeneration and cardiac failure. Preclinical and a limited number of clinical studies suggest that, whereas antioxidants in general do not prevent doxorubicin cardiotoxicity, administration of coenzyme Q10 does prevent the development of both acute and chronic cardiotoxicity without interfering with the drug’s anticancer efficacy (1). This is another area that warrants further investigation.

Oxidative stress induced by low levels of hydrogen peroxide has been shown to elevate the LD50 of several types of antineoplastic agents and to block drug-induced apoptosis in neoplastic cells, causing cells to undergo necrosis instead of apoptosis (15,16). These effects of hydrogen peroxide are prevented by the addition of certain antioxidants. The reduced cytotoxicity of anticancer agents in the presence of hydrogen peroxide, an effect that also might occur during chemotherapy-induced oxidative stress, may result from the effects of the cellular products generated by ROS.

Free radicals generated during oxidative stress have many cellular targets, but one of the primary targets is cellular lipids. Lipid peroxidation of PUFA results in formation of alkoxyl and peroxyl radicals (primary products) that are highly reactive and relatively short-lived. Secondary products of lipid peroxidation include numerous aldehydes, including malondialdehyde, the 4-hydroxyalkenals, and acrolein (17). These electrophilic compounds are more stable than the primary products, and they can diffuse throughout the cell where they can damage cellular components and interfere with cellular functions. The aldehydes are potent enzyme inhibitors because they bind to nucleophilic groups of amino acids, such as cysteine, lysine, histidine, serine, and tyrosine, that are critical components of enzyme active sites or necessary for maintaining the tertiary structure of enzymes.

Oxidative stress, possibly through aldehyde-mediated enzyme inhibition of cyclin-dependent kinases, inhibits transition of cells from the G0 phase (quiescent phase) of the cell cycle to the G1 phase, blocks progression through the restriction point, and causes arrest of the cell cycle at the G1, S, G2, and M phase checkpoints (18). For antineoplastic agents that exhibit cell cycle phase-specific activity, e.g., those that interfere with DNA synthesis or block the mitotic process, interference with cell cycle progression may diminish their cytotoxicity. Even platinum coordination complexes and alkylating agents, which are not considered to be phase-specific agents, require cells to progress through the S phase and G2 phase for apoptosis to occur. Checkpoint arrest also may allow for DNA repair of damage caused by platinum coordination complexes and alkylating agents, and checkpoint abrogation (the opposite of what happens during oxidative stress) has been shown to enhance the cytotoxicity of several types of antineoplastic agents. By reducing aldehyde generation, antioxidants may counteract the effects of chemotherapy-induced oxidative stress on cell cycle progression and enhance the cytotoxicity of antineoplastic agents.

Aldehydes also may directly interfere with the major pathways of chemotherapy-induced apoptosis, namely, the CD95/CD95 ligand (Fas/Apo1) death receptor pathway and the pathway initiated by cytochrome c release from mitochondria (5). The CD95 death receptor has a cysteine-rich extracellular domain, making it a potential target for binding by strong electrophiles such as the aldehydes. Binding of aldehydes to death receptors may mimic the effect of death receptor antibodies that interfere with ligand binding and block drug-induced apoptosis.

Whereas oxidative stress can act as a trigger for cytochrome c release and initiate apoptosis, excessive oxidative stress is an effective inhibitor of caspases (and procaspase activation) (19,20), the enzymes that carry out the apoptotic process. Caspases are cysteine proteases, possessing a cysteine moiety at their active sites, and require a reducing environment for optimal activity. Caspase inhibition, such as that caused by the cowpox virus CrmA protein when it is overexpressed in leukemic cells, confers resistance to a variety of antineoplastic agents (21). Electrophilic aldehydes, such as acetyl-tetrapeptide (22), also bind to the active site of caspases and inhibit their activity. Thus, aldehyde generation, resulting in caspase inhibition, may account for the reduced efficacy of antineoplastic agents during oxidative stress. If so, antioxidants may enhance the anticancer activity of cancer chemotherapeutic agents by reducing aldehyde generation that is caused by chemotherapy-induced oxidative stress.

Future research needs to address many unanswered questions regarding the impact of oxidative stress on the therapeutic efficacy of cancer chemotherapy, the role that oxidative stress plays in the development of chemotherapy-induced side effects, and the effect of antioxidants on anticancer activity and the development of therapy-induced adverse effects. Fundamental studies that elucidate the impact of oxidative stress, and specifically ROS-generated aldehydes, on cell cycle progression and apoptotic pathways may guide us to interventions that could enhance chemotherapeutic efficacy. Further investigation of GSH for preventing cisplatin toxicity and coenzyme Q10 for preventing doxorubicin cardiotoxicity appears to be indicated based upon existing studies. Finally, clinical studies must be conducted to determine both the short-term and long-term impact of antioxidants, singly and in combination, upon the efficacy of cancer chemotherapy and the development of chemotherapy-induced side effects.

 

FOOTNOTES

1 Presented as part of the conference “Free Radicals: The Pros and Cons of Antioxidants,” held June 26–27 in Bethesda, MD. This conference was sponsored by the Division of Cancer Prevention (DCP) and the Division of Cancer Treatment and Diagnosis, National Cancer Institute, NIH, Department of Health and Human Services (DHHS); the National Center for Complementary and Alternative Medicine (NCCAM), NIH, DHHS; the Office of Dietary Supplements (ODS), NIH, DHHS; the American Society for Nutritional Science; and the American Institute for Cancer Research and supported by the DCP, NCCAM, and ODS. Guest editors for the supplement publication were Harold E. Seifried, National Cancer Institute, NIH; Barbara Sorkin, NCCAM, NIH; and Rebecca Costello, ODS, NIH. Back

3 Abbreviations used: GGT, γ-glutamyl transpeptidase; GSH, glutathione; NAC, N-acetyl cysteine; ROS, reactive oxygen species. Back

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Antioxidants and other nutrients do not interfere with Chemotherapy or Radiation Therapy and can increase Kill and increase Survival

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Posted 09 Jun 2011 — by James Street
Category antioxidants, antioxidants, Chemotherapy, Radiation

Antioxidants and other nutrients do not interfere with Chemotherapy or Radiation Therapy and can increase Kill and increase Survival Part I

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