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Effect of medroxyprogesterone acetate (MPA) and serum factors on cell proliferation in primary cultures of an MPA-induced mammary adenocarcinoma
Authors:Graciela Dran  Isabel A Luthy  Alfredo A Molinolo  Fernanda Montecchia  Eduardo H Charreau  Christiane Dosne Pasqualini  Claudia Lanari
Institution:(1) División Medicina Experimental, Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina & Instituto de Biología y Medicina Experimental, Pacheco de Melo 3081, 1425 Buenos Aires, Argentina
Abstract:Summary The effect of progesterone (Pg), medroxyprogesterone acetate (MPA), estradiol (E2), dihydrotestosterone (DHT) and dexamethasone (DEXA) was studied on thein 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 fibroblastenriched cultures using3H-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 stimulated3H-thyrnidine 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/105 cells, n = 5) and estrogen receptors (ER) (ND-115 fmoles/105 cells, n = 5) were detected only in epithelial-enriched cultures. Serum from 7 day-MPA-treated mice induced a significant increase of3H-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.
Keywords:cell proliferation  mammary tumors  medroxyprogesterone acetate  primary cultures  progestins  serum factors
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