Enhancement of DMBA-induced mammary cancer in Wistar rats by unsaturated fat and cholestyramine.

Promotion of 7,12-dimethylbenzantracene (DMBA)-induced mammary cancer in Wistar rats, by diets containing unsaturated fat (USF) and unsaturated fat plus 4% cholestyramine (USF+ CHST) was compared to that in rats fed saturated fat (SF). The diets were fed for 100 or 200 days. Histologic examination of grossly normal mammary tissue, as well as of any tumor mass, showed a significant increase in the incidence and size of mammary tumors in USF and USF + CHST groups when compared to SF group. Moreover, in the USF + CHST group one tumor developed in one rat as early as 100 days. The serum total lipids, triglycerides and cholesterol esters decreased significantly at 200 days in USF and USF + CHST groups. These results suggest that a diet high in unsaturated fat alone, or in combination with 4% cholestyramine, promotes DMBA-induced mammary cancer in Wistar rats.