Experimental combined hormone therapy on human breast carcinomas serially transplanted into nude mice.

Experimental combined hormone therapy with tamoxifen, aminoglutethimide and medroxyprogesterone acetate was investigated using three hormone-dependent human breast carcinomas serially transplanted into nude mice. The antitumor effect of combined tamoxifen and aminoglutethimide was better than that of either tamoxifen or aminoglutethimide alone. Since aminoglutethimide significantly reduced the level of estrogen and the uterine weight in normal female mice, the antitumor effect of combined tamoxifen and aminoglutethimide was assumed to be a result of the low estrogen level produced by aminoglutethimide, favoring the competition of tamoxifen with estrogen receptors. There was no additive antitumor effect of the combination of tamoxifen and medroxyprogesterone acetate, although serum medroxyprogesterone acetate levels in nude mice were almost equivalent to those of humans. These results indicate that combination hormone therapy, especially with and aminoglutethimide, might be a promising method for clinical application.