title: Synergistic tumor promoter effects of estrone and progesterone in methylnitrosourea-induced rat mammary cancer.
abstract: Tumor promoter effects of steroid hormones were tested in ovariectomized rats treated with the tumor initiator, methylnitrosourea. Continuous treatment with low doses of estrone induced tumor in 55% of experimental animals while intact control animals had a 96-100% incidence. Although progesterone alone produced no tumors in ovariectomized, methylnitrosourea-treated animals, estrone and progesterone acted synergistically, inducing tumorigenesis in 88% of treated rats. These results point to an important interaction between estrogens and progestins in promoting mammary tumorigenesis.
authors.affiliation: Department of Obstetrics and Gynecology, Indiana University School of Medicine, 975 West Walnut Street (IB360), Indianapolis, IN 46202, USA. rbigsby@iupui.edu
authors.forename: Robert M
authors.initials: RM
authors.lastname: Bigsby
mesh_terms: D000477:Alkylating Agents / Q000633:toxicity*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004357:Drug Synergism; D004970:Estrone / Q000494:pharmacology*; D005260:Female; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000473:pathology*; D008770:Methylnitrosourea / Q000633:toxicity*; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects / Q000254:growth & development; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014599:Uterus / Q000187:drug effects / Q000254:growth & development
chemical_list: D000477:Alkylating Agents; D004970:Estrone; D011374:Progesterone; D008770:Methylnitrosourea