(12-12-05) Dietary fish oil curbs breast cancer progression in animal study

NEW YORK (Reuters Health) - The growth of breast cancer cells in culture and in mice is inhibited by omega-3 fatty acids, scientists report in a fast track article in the November 10th International Journal of Cancer.

According to Dr. Rafat A. Siddiqui from the Methodist Research Institute, Clarian Health Partners in Indianapolis, "Omega-3 fatty acids activate an enzyme called sphingomyelinase, which generates the release of ceramide, a compound that ultimately causes cancer cell death."
Most American and British diets are high in omega-6 fatty acids (common in beef products) and low in omega-3 fatty acids (common in fish oils), noted the researcher. In a number of human studies, diets rich in omega-3 fatty acids were associated with a lower risk of breast and colon cancers. However, the mechanisms by which these dietary fats affect development and growth of cancers has been unclear.
Dr. Siddiqui and colleagues set out to determine if dietary lipids could modulate growth of breast cancer cells in animals and to determine the cellular mechanisms by which dietary lipids alter growth of breast cancer cells.
In the animal study, mice were fed diets rich in omega-3 (fish oil) or omega-6 (corn oil) fatty acids. Three weeks after implantation of breast cancer cells, tumor volume and weight were significantly lower in the omega-3 group compared with the omega-6 group.
The omega-3-rich diet also led to a 40% increase in sphingomyelinase and increased expression of p21, which is associated with growth arrest.
Similar results were seen in cultured breast cancer cells.
"Our study shows that dietary intake of different fatty acids affects the growth of breast cancer cells," Dr. Siddiqui said.
"Dietary fatty acids," he explained, "are incorporated into cell membranes, and the type of fatty acids dictates the localization of key signaling molecules within the cell. These signaling molecules then regulate cell growth."
"Our studies indicate that sphingomyelinase, an enzyme usually present in lipid rafts located within the cell membrane, changes its localization in the cell in the presence of omega-3 fatty acids, possibly due to changes in the structure of the lipid rafts," the researcher said.
This study, Dr. Siddiqui concluded, "suggests that incorporating moderate amounts of omega-3 fatty acids into the diet may decrease breast cancer progression. Importantly, omega-3 fatty acids are already known to have beneficial cardiovascular effects in humans."

Source : Int J Cancer 2005;117:340-343.

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