Protective effects of progesterone and tamoxifen in estrogen-induced mammary carcinogenesis in ovariectomized W/Fu rats.
The protective effect of progesterone or tamoxifen, an antiestrogenic agent, was investigated in estrogen-induced mammary carcinogenesis. Multiple mammary tumors (MT) of tubular or medullary carcinoma type developed at a high rate following prolonged treatment of ovariectomized W/Fu rats with diethylstilbestrol or 17 beta-estradiol. All MTs were located adjacent to the nipple and were slow-growing. The induction rate, multiplicity and size of estrogen-induced MTs were reduced by the simultaneous administration of either progesterone or tamoxifen. The estrogen-induced pituitary tumorigenesis was effectively inhibited by tamoxifen treatment, but it was not affected by progesterone. The results indicated that the inhibitory effect of progesterone or tamoxifen in estrogen-induced carcinogenesis is attributable to interference with the binding of estrogen to the estrogen receptors on the target cells.
D000236:Adenoma / Q000139:chemically induced / Q000473:pathology; D000818:Animals; D002277:Carcinoma / Q000032:analysis / Q000139:chemically induced* / Q000473:pathology; D004054:Diethylstilbestrol; D004958:Estradiol; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D008321:Mammary Glands, Animal / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000032:analysis / Q000139:chemically induced* / Q000473:pathology; D010052:Ovariectomy; D010911:Pituitary Neoplasms / Q000139:chemically induced / Q000473:pathology; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011920:Rats, Inbred WF; D011960:Receptors, Estrogen / Q000032:analysis; D013629:Tamoxifen / Q000494:pharmacology*
D004967:Estrogens; D011960:Receptors, Estrogen; D013629:Tamoxifen; D011374:Progesterone; D004958:Estradiol; D004054:Diethylstilbestrol