17 beta-Estradiol-mediated growth inhibition of MDA-MB-468 cells stably transfected with the estrogen receptor: cell cycle effects.
Estrogen receptor (ER)-negative MDA-MB-468 human breast cancer cells were stably transfected with wild-type human ER and utilized as a model for investigating estrogen- and aryl hydrocarbon (Ah)-responsiveness. Treatment of the stably transfected cells with 10 nM 17 beta-estradiol (E2) resulted in a significant inhibition (> 60%) of cell proliferation and DNA synthesis, which was blocked by 10(-7) M ICI 182 780. Analysis by flow cytometry indicated that treatment with E2 increased the percentage of cells in G0/G1 (from 68.8 to 89.4) and decreased cells in S (from 18.4 to 3.4) and G2/M (from 12.8 to 7.2) phases of the cell cycle. The effects of E2 on the major cyclins, cyclin-dependent kinases and cyclin-dependent kinase inhibitors, retinoblastoma protein (RB), E2F-1, and cyclin-dependent kinase activities were also investigated in the stably transfected MDA-MB-468 cells. The results demonstrated that the growth inhibitory effects of 10(-8) M E2 in ER stably transfected MDA-MB-468 cells were associated with modulation of several factors required for cell cycle progression and DNA synthesis, including significant induction of the cyclin-dependent kinase inhibitor p21cip-1 ( > 4-fold increase after 12 h) and decreased E2F1 and PCNA protein levels. These results show that the growth-inhibitory effects of E2 in the stably transfected cells were due to multiple factors which result in growth arrest in G0/G1 and inhibition of DNA synthesis.
Wang
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Department of Veterinary Physiology, Texas A&M University, College Station 77843-4466, USA.
Smith
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Burghardt
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Safe
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D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics*; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology*; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D011960:Receptors, Estrogen / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D006131:Growth Inhibitors; D011960:Receptors, Estrogen; D004958:Estradiol