Inhibitory effects of progesterone on plasma membrane fluidity and tumorigenic potential of ovarian epithelial cancer cells.

The lethality of common (surface) epithelial ovarian cancer is contingent on its metastatic capacity. Dissemination of the neoplasia throughout the abdominal cavity has been associated with secretion of proteolytic enzymes from vesicles shed by ovarian cancer cells. We report that the lipophilic steroid hormone progesterone decreases the fluid dynamics of plasma membranes of human SKOV-3 adenocarcinoma cells. The decrease in membrane fluidity was related to an inhibition in vitro of exocytotic vesicle release, cellular invasiveness into Matrigel, and colony formation in three-dimensional collagen matrix. Tumorigenesis was suppressed by progesterone in immunocompromised nude mice inoculated intraperitoneally with SKOV-3 cells. Progestins could therefore be of benefit in the prevention and(or) treatment of early-stage ovarian carcinomatosis.