The production of plasminogen activator by the human breast cancer cell line MCF-7 was stimulated by physiological concen trations of estradiol under conditions where the growth of the cells was neither dependent on nor stimulated by estradiol. Stimulation was measurable within 8 hr after the addition of estradiol and was evident in both the level of plasminogen activator released into the culture medium and the level within the cells. The level of production varied with cell density, but production was stimulated by estradiol at all densities tested. The antiestrogen tamoxifen inhibited estrogen stimulation, and this inhibiton could be overcome by increased concentrations of estradiol. Production was also stimulated by progesterone and could be stimulated by lower levels of progesterone in cells pretreated with estradiol or tamoxifen, both of which have bee
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.