Fish Oil Concentrate Increases Doxorubicin Efficacy in Animals

WASHINGTON—Adding fish oil to the diet of mice implanted with human breast cancer cells increased the efficacy of doxorubicin while reducing hematologic side effects, W. Elaine Hardman, PhD, of the University of Texas Health Science Center at San Antonio, said at the Susan G. Komen Breast Cancer Foundation grants conference.

Dr. Hardman and Ivan L. Cameron, PhD, compared diets containing two different oils. They began by inoculating mice with tumor cells and feeding them a standard diet until the tumors reached about 5 mm in diameter. Then they switched the diet to include either 5% corn oil or a 3% fish oil concentrate containing omega-3 and omega-6 fatty acids. After a further 2 weeks, they initiated chemotherapy with doxorubicin.

The oil concentrated at the tumor sites, Dr. Hardman said. Tumor levels of fatty acids were 57 times higher than before the fish oil diet, while the liver registered levels only 21 times higher.

In the mice fed corn oil, doxorubicin slowed tumor growth but also decreased red and white blood cell counts. In the mice given doxorubicin and fish oil, however, red blood cell counts were maintained and there was less reduction in white blood cell counts. Similar effects of fish oils have been observed with irino-tecan (Camptosar), she said.

Most chemotherapy drugs cause oxidative damage, which will cause cells to die if they cannot upregulate levels of protective antioxidant enzymes. This effect potentiates the chemotherapeutic action in the tumor cells but is harmful to normal cells. However, if the normal cells can be induced to upregulate protective enzymes, they will not be as damaged as the tumor cell. This, she hypothesizes, is the effect of the omega-3 and omega-6 fatty acids in the fish oil concentrate.

Fish oil alone suppressed tumor growth, and the combination of fish oil concentrate and doxorubicin caused the cells to regress significantly.

The amount of fish oil fed to the mice was the equivalent in a human diet of 8 to 10 g/day, a reasonable clinical dose, Dr. Hardman said. She hopes to begin clinical trials in humans shortly.