Progesterone-specific stimulation of triglyceride biosynthesis in a breast cancer cell line (T-47D).

The purpose of this study was to examine the lactogenic response of human mammary cancer cell lines to hormones in vitro. Progesterone was found to stimulate the incorporation of 14C from [14C]acetate into triglycerides (TG) and to promote accumulation of TG with a fatty acid composition similar to that of human milk fat in T-47D cells. Lipid droplets were observed in larger numbers without concomitant accumulation of casein granules in cells incubated with progesterone, but secretion of lipid into the medium did not occur. An effect of progesterone on TG accumulation was detectable after 12 hr and was maximal at 72 hr. Increasing doses of progesterone (10(-9) to 10(-5) M) caused a progressive increase in TG accumulation. The presence of cortisol and/or prolactin did not alter TG formation nor the dose response of the cells to progesterone. The growth rate of T-47D cells was not altered by the presence of progesterone in the medium. Neither of the human mammary cancer cell lines, MCF-7 and HBL-100, nor the human fibroblast cell lines, 28 and 857, responded to progesterone. The data indicate that, while the normally lactogenic hormones do not stimulate milk product biosynthesis in the cell lines tested, progesterone specifically stimulated synthesis and accumulation of TG in the T-47D cells.