WASHINGTONAdding 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.