Combined effects of buserelin, estradiol and tamoxifen on the growth of MCF-7 human breast cancer cells in vitro.

The growth-stimulation of MCF-7 human breast cancer cells in vitro induced by 30 pM estradiol was inhibited both by the LHRH-agonist Buserelin and the anti-estrogen Tamoxifen used as single agents. Combined administration of both drugs was less effective in this respect. In the presence of estradiol Buserelin had no effect on the pattern of [35S]methionine labelled secretory proteins when examined with one-dimensional gel electrophoresis, whereas the estrogen-induced progesterone receptor synthesis was inhibited. Thus with estradiol concentrations comparable to plasma values in medically castrated patients, the LHRH-agonist Buserelin can directly inhibit breast cancer cell growth in vitro.