Enzymes of the fatty acid synthesis pathway are highly expressed in in situ breast carcinoma.

Expression of high levels of fatty acid synthase (FAS), an important enzyme in fatty acid synthesis, has been identified in a wide variety of human carcinomas. In breast and prostate carcinoma, FAS expression appears to be associated with aggressive disease. Recent biochemical studies have demonstrated that FAS expression in cancer cells connotes activation of the entire fatty acid synthesis pathway leading to the production of palmitic acid. Here, we explore the immunohistochemical expression of FAS and human acetyl-CoA carboxylase (HACC), the rate-limiting enzyme in fatty acid synthesis, in breast cancer progression from histologically normal breast through the development of in situ duct and lobular carcinoma to infiltrating carcinoma. Both FAS and the Mr 275,000 isoform of HACC are expressed in a small subset of cells in normal breast lobules and terminal ducts. Upon development of either in situ duct or lobular carcinoma, FAS and both isoforms of HACC are expressed at higher levels and in a majority of the cells. These findings suggest that expression of the enzymes of fatty acid synthesis are frequently altered early in the progression of human breast carcinoma.