Regression of "hormone-independent" DMBA-induced mammary carcinomas in response to GP 48989 and its effects on hormone receptors.

GP 48 989 causes regression of DMBA-induced mammary carcinomas of spayed ("hormone-independent"), non spayed (approximately 5% "hormone-dependent") rats and of tumors which had become refractory to estradiol treatment. Since no binding to the cytoplasmic estradiol receptor after prolonged intramuscular treatment was found, the compound does not act as a classical anti-estrogen.