title: Effect of medroxyprogesterone acetate (MPA) and serum factors on cell proliferation in primary cultures of an MPA-induced mammary adenocarcinoma.
abstract: The effect of progesterone (Pg), medroxyprogesterone acetate (MPA), estradiol (E2), dihydrotestosterone (DHT) and dexamethasone (DEXA) was studied on the in vitro growth rate of a progestin-dependent (PD), estrogen-sensitive mammary tumor line originated in an MPA-treated BALB/c mouse (C4-HD), and on its estrogen-resistant variant (C4-HDR). The specificity of hormone action was further investigated using the anti-hormones RU-486 and hydroxyflutamide (FLU). Cell growth was evaluated in epithelial and fibroblast-enriched cultures using 3H-thymidine and/or autoradiography and immunocytochemistry. The results indicate that cell growth is directly stimulated by MPA and Pg at concentrations ranging from 10(-11) to 10(-7) M. RU486 prevented MPA-induced stimulation in concentrations 10 to 100 fold lower than those of MPA. When used alone, it inhibited cell proliferation only in concentrations higher than 10(-11) M. At nM concentrations, neither DEXA nor DHT stimulated 3H-thymidine uptake except DEXA at 100 nM. MPA-induced stimulation was not reverted by micromolar concentrations of FLU. As for E2 (10(-7)-10(-9) M) it prevented MPA stimulation only in cultures of estrogen-sensitive tumors. Progesterone receptors (PR) (475 +/- 115 fmoles/10(5) cells, n = 5) and estrogen receptors (ER) (ND-115 fmoles/10(5) cells, n = 5) were detected only in epithelial-enriched cultures. Serum from 7 day-MPA-treated mice induced a significant increase of 3H-thymidine uptake; an increase was also obtained with serum from untreated ovariectomized animals to which 1 nM-100 nM concentrations of MPA had been added. The stimulatory effect of the exogenous MPA was much lower than that of the serum obtained from MPA-treated animals. It is concluded that MPA stimulates cell growth of primary cultures of MPA-induced PD tumors via PR. The results provide support for a direct effect of MPA which may be mediated or potentiated by serum factors.
authors.affiliation: División Medicina Experimental, Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina, Buenos Aires, Argentina.
authors.forename: G
authors.initials: G
authors.lastname: Dran
authors.forename: I A
authors.initials: IA
authors.lastname: Luthy
authors.forename: A A
authors.initials: AA
authors.lastname: Molinolo
authors.forename: F
authors.initials: F
authors.lastname: Montecchia
authors.forename: E H
authors.initials: EH
authors.lastname: Charreau
authors.forename: C D
authors.initials: CD
authors.lastname: Pasqualini
authors.forename: C
authors.initials: C
authors.lastname: Lanari
mesh_terms: D000230:Adenocarcinoma / Q000097:blood / Q000139:chemically induced / Q000473:pathology*; D000726:Androgen Antagonists / Q000494:pharmacology; D000818:Animals; D001790:Blood Physiological Phenomena; D002455:Cell Division / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005485:Flutamide / Q000031:analogs & derivatives / Q000494:pharmacology; D008325:Mammary Neoplasms, Experimental / Q000097:blood / Q000473:pathology*; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D015735:Mifepristone / Q000494:pharmacology; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000726:Androgen Antagonists; D013196:Dihydrotestosterone; C014290:hydroxyflutamide; D015735:Mifepristone; D011374:Progesterone; D004958:Estradiol; D005485:Flutamide; D003907:Dexamethasone; D017258:Medroxyprogesterone Acetate