[Effects of metformin on the estrogen-induced proliferation and the expression of ER in human endometrial cancer cells].
To assess the effects of metformin on estrogen-induced proliferation of human endometrial cancer cell lines and investigate whether metformin could regulate the expression of ER and estrogen-dependent proliferative genes.Human endometrial cancer cell lines Ishikawa and HEC-1A underwent treatment with metformin at various concentrations (0.5, 1, 5, 10, 15, 20, 25 and 30 mmol/L) for different durations (24, 48 and 72 hours), followed by assessment of cell proliferation by methyl thiazolyl tetrazolium (MTT) assay. Ishikawa and HEC-1A cells were exposed to 17β-estradiol (1×10(-6) mol/L) alone or in combination with metformin (5 mmol/L) for 24 hours. Cell proliferation was assessed by 5-bromo-2-deoxyuridine (BrdU) assay. Twenty-four hours after metformin treatment at the concentrations of 1, 5 and 15 mmol/L, the expression levels of estrogen-dependent proliferative genes c-fos and c-myc were determined by real-time quantitative fluorescent PCR (real-time FQ-PCR). Western blot analysis was performed to assess the effects of metformin on the expressions of estrogen receptors.As revealed by MTT assay, at different time points of metformin treatment at different concentrations, the proliferation rates of both cell lines were inhibited in a dose-dependent and time-dependent manner between metformin groups and the control group (P < 0.05). BrdU assay showed that the proliferation rate of Ishikawa and HEC-1A cells exposed to 17β-estradiol (1×10(-6) mol/L) in combination with metformin (5 mmol/L) was (62±7)% and (72±6)%, respectively, while that in 17β-estradiol groups was (124±16)% and (109±5)%, respectively, with significantly statistical differences (P < 0.01). By real-time FQ-PCR tested, the expression levels of c-fos and c-myc in both cell lines gradually declined subsequent to metformin treatment at different concentrations (1, 5 and 15 mmol/L). As compared with the control group, the c-myc and c-fos expressions in both cell lines in metformin groups had significant differences (P < 0.05) except for the c-myc expression of the concentration of 1 mmol/L in HEC-1A cell line (P = 0.074). Western blot analyses showed that with the increasing concentrations of metformin, the ERa expression was markedly down-regulated, while ERβ expression was up-regulated in the metformin group at the concentrations of 5 mmol/L and 15 mmol/L, compared to those at the control group, there were significant differences between them, respectively (all P < 0.01).Metformin could inhibit estrogen-mediated proliferation of human endometrial cancer cells, which might be correlated with its regulation of the expressions of estrogen receptors and estrogen-dependent proliferative genes.