Hypophysectomy and injections of high doses of estrogens inhibit the growth of ovary-independent rat mammary carcinomas.

Estrogen receptor-negative, 7, 12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinoma (TF1357) grew equally well in ovariectomized females, ovariectomized females with thyroidectomy and ovariectomized females given injections of Tamoxifen (0.1 mg/day), Medroxyprogesterone acetate (8 mg/day) or CB-154 (1 mg/day). However, the growth of TF1357 was inhibited markedly by injections of a very large amount of 17 beta-estradiol (1 mg/2 days) and also by hypophysectomy. The growth of estrogen receptor-positive, DMBA-induced rat mammary carcinoma (8K2401) was also almost completely inhibited by hypophysectomy and injections of high doses of 17 beta-estradiol, while 8K2401 grew well in castrated males. Secretory changes characterized by vacuolation in cytoplasm were observed in 8K2401 cells in castrated males with injections of high doses of estrogen but these changes were not found in 8K2401 cells in castrated males with hypophysectomy or in TF1357 cells in ovariectomized females which had had hypophysectomy or injections of high doses of estrogen. These observations suggest that hypophysectomy and/or injections of high doses of estrogen may be effective treatment for breast cancer unresponsive to ovariectomy or injections of antiestrogen drugs.