Effects of estrogens and antiestrogens on androgen-dependent growth of Shionogi carcinoma 115: Role of estrogen receptor

Experiments were performed to observe the role of estrogen receptor in the proliferation of androgen-dependent mouse tumor, Shionogi carcinoma 115. Estradiol and diethylstilbestrol inhibited tumor growth as well as the weight gain of seminal vesicles and prostate glands in intact male mice. Tamoxifen decreased the tumor weight in intact males. Both nitromifene given to intact mice and tamoxifen given to castrated androgenized mice decreased the weight of seminal vesicles, but increased tumor weight. Estradiol was bound to the androgen receptor of the tumor cytosol with relatively high affinity, whereas diethylstilbestrol, tamoxifen and nitromifene were not. These were effective competitors in the estrogen receptor present in the tumor cytosol. These results suggest that the estrogen receptor system in Shionogi carcinoma 115 inhibits the proliferation of tumor cells.