Effect of pharmacological doses of estrogen on ovary-independent rat mammary carcinoma containing estrogen and progesterone receptors.
Mammary carcinoma induced in male Sprague-Dawley rats by multiple intragastric intubations of 7,12-dimethylbenz-(a)anthracene showed ovary-independent growth but contained estrogen receptors (ER) and progesterone receptors (Yoshida, Yoshida. Fukunishi, Sato, Okamoto, and Matsumoto, Cancer Res., 42: 2434-2439, 1982). Transplantable carcinoma (MT6) was obtained from dimethylbenz(a)anthracene-induced mammary carcinoma and then maintained in male rats. MT6 tumors with ER grew equally well in males, females, gonadectomized males, males given injections of bromocryptine (1 mg/day) or lisuride hydrogen maleate (50 micrograms/day), and gonadectomized males receiving smaller doses of 17 beta-estradiol (1 to 100 micrograms/2 days). However, the growth of MT6 was inhibited markedly by injection of a very large amount of 17 beta-estradiol (1 mg/2 days). Although transplanted MT6 tumors were ductal carcinoma with cribriform pattern with ER, tumors recurring after injection with 1 mg 17 beta-estradiol were found to be spindle cell carcinoma without ER, which could grow equally well in recipients treated with or without 1 mg 17 beta-estradiol. These observations suggest that the growth of ovary-independent MT6 tumors with ER and progesterone receptors is inhibited only by pharmacological doses of estrogens and that the loss of growth-inhibiting effect of pharmacological doses of estrogen of MT6 tumors occurs during high-dose estrogen treatment.
D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002277:Carcinoma / Q000473:pathology*; D002369:Castration; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*; D009368:Neoplasm Transplantation; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000032:analysis*; D011980:Receptors, Progesterone / Q000032:analysis*; D013997:Time Factors
D004967:Estrogens; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D004958:Estradiol; D015127:9,10-Dimethyl-1,2-benzanthracene