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Fish oil appears to make chemotherapy more effective, study finds (8-6-99)

New studies in press with the British Journal of Cancer suggest that, in mice at least, consumption of a diet enhanced with fish oil helped a chemotherapy drug to work more effectively against cancer cells, and also reduced intestinal damage caused by the drug.

The researchers, W. Elaine Hardman, Ph.D., Mary Pat Moyer, Ph.D., and Ivan Cameron, Ph.D., of The University of Texas Health Science Center at San Antonio, noted significantly increased tumor regression in mice receiving fish oil-enhanced diets. The findings are so promising, Dr. Hardman said, that the researchers have proposed a clinical trial in humans to the National Cancer Institute. The chemotherapy drug in the study was CPT-11 (irinotecan).

Dr. Hardman, research assistant professor in the Department of Cellular and Structural Biology, and Dr. Cameron, professor of cellular and structural biology, compared groups of mice on normal diets and fish oil-added diets. The fish oil-supplemented group of mice received a low dose of specially processed omega-3 fatty acids (fish oil), equivalent to a human consumption of 10 to 12 grams of fish oil per day.

"While the chemotherapy stopped growth of the implanted breast cancers in mice eating a normal diet, in those mice eating a fish oil-added diet the tumors were significantly reduced and the intestinal damage caused by CPT-11 was ameliorated," Dr. Hardman said. "We therefore know that the chemotherapy worked better with the fish oil diet. We've also tried this with two other chemotherapy drugs, doxorubicin and edelfosine, and have shown that the fish oil diet enhanced the efficacy of those drugs. We are studying several hypotheses to explain these effects."

Salmon, striped bass, swordfish and tuna are rich sources of omega-3 fatty acids, and scientists previously have shown these fatty acids slow or prevent tumor growth. The new study is one of the first to show the impact of fish oil on the effectiveness of cancer chemotherapy, however.

Walnuts, soybeans, canola oil and flaxseed are other less-concentrated sources of omega-3 fatty acids. Dr. Hardman emphasized that the tumor regression findings were based on use of specially processed and formulated omega-3 fatty acids, and cannot be extrapolated to consumption of currently available fish oil products.

Hundreds of thousands of U.S. cancer patients receive cancer chemotherapy each year. Although it results in cancer remission in many cases, side effects such as intestinal problems cause therapy to be stopped in other patients.

Omega-3 fatty acids may make it easier for chemotherapy drugs to damage a cancer cell's membrane. "Studies suggest that the more of the omega-3 fatty acids that cancer cells incorporate, the more sensitive they become to damage by certain chemotherapeutic drugs," Dr. Hardman said. "Left unchecked, this damage can initiate a chain reaction that ultimately kills the cancer cell."

The research is funded by the American Institute for Cancer Research, the Susan G. Komen Breast Cancer Foundation and a small business technology transfer grant from the National Cancer Institute in collaboration with INCELL Corp.

INCELL is a San Antonio biotechnology company headed by Dr. Moyer, CEO of INCELL and part-time professor at the Health Science Center. The fish oil formulation used in the study will soon be marketed by INCELL as a nutritional supplement only, pending clinical studies to validate its use in humans. The product will be called INCELL-AFFA™.

Contact: Will Sansom