Growth stimulatory activity of unsaturated fatty acids for normal and neoplastic breast epithelium

Studies with experimental animals first showed that dietary lipids in excess have a very large stimulatory effect on the development of breast tumors either induced by carcinogens or occurring spontaneously. These observations took on added significance when epidemiologists found a strong positive correlation between breast cancer incidence and the level of dietary fat. Although not unequivocably established, the total observations concerning this phenomenon suggest a cause and effect relationship between high dietary lipids and breast cancer development. In an attempt to understand how the lipids might be acting, we have begun to assess the effects of various fatty acids on the growth and function of breast epithelium from both normal and neoplastic tissue. The results to date suggest that the unsaturated fatty acids are needed for mammary cell division and that they may play roles in this process by serving as substrates for prostaglandin synthesis, as membrane structural elements or possibly as activators of C kinase when they are in the form of diglycerides. Whatever the mechanism of growth stimulation, it appears that the fatty acids are rate limiting for growth and that physiologic mechanisms for recruiting fatty acids from proximal fat cells exist within the mammary gland. It thus appears that the fat cell serves as a physiologic buffer and that exceeding this buffer such as by consuming excessive lipids may override this buffering capacity and thus favor the division of normal or neoplastic breast cells.