Dietary effects of mead acid on N-methyl-N-nitrosourea-induced mammary cancers in female Sprague-Dawley rats

The effect of mead acid (MA; 5,8,11-eicosatrienoic acid) on the suppression of the development and growth of N-methyl-N-nitrosourea (MNU)-induced mammary cancer in female Sprague-Dawley rats was examined. The MA diet (2.4% MA) or control (CTR) diet (0% MA) was started at 6 weeks of age, MNU was injected intraperitoneally at 7 weeks of age, and the rats were maintained on the respective diets for the whole experimental period (until 19 weeks of age). All induced mammary tumors were luminal A subtype carcinomas (estrogen and progesterone receptor positive and HER2/neu negative). The MA diet significantly suppressed the initiation and promotion phases of mammary carcinogenesis; MA suppressed the development (incidence, 61.5 vs. 100%; multiplicity, 2.1 vs. 4.5) and the growth (final tumor weight, 427.1 vs. 1,796.3 mg) of mammary cancers by suppressing cell proliferation, but not by accelerating cell death. There were evident changes in the major fatty acid composition of n-3, n-6, and n-9 fatty acids in the serum of the MA diet group; there was a significant increase in MA and significant decreases in oleic acid (OA), linoleic acid, arachidonic acid and docosahexaenoic acid. In non-tumorous mammary tissue, there was a significant increase in MA and a significant decrease in OA in the MA diet group. The n-6/n-3 ratios in serum and mammary tissue of the MA diet group were significantly decreased. The MA diet suppressed MNU-induced luminal A mammary cancer by lowering cancer cell proliferation. Therefore, MA may be a chemopreventive and chemotherapeutic agent. In addition to hormone therapy, MA supplementation may be a beneficial chemotherapeutic agent for the luminal A subtype of breast cancer.