Estradiol activated microrna 23a directly or synergistically with p53 implicated in sex difference in hepatocellular carcinoma development

Abstract

BACKGROUND: Estrogen (E2) exerts a protective role against hepatocellular carcinoma (HCC) development. We sought to determine the effects of E2 on apoptotic miRNAs expression and explore the possible mechanism underlying apoptosis in HCC. METHODS: Microarray was performed to analyze alteration of apoptotic miRNAs in E2-treated liver cell-line. Expression profiles of selected miRNAs were verified using qRT-PCR. qRT-PCR and Western-blot were used to analyze the alteration of mRNA and protein levels of genes such as p53, ERa, XIAP and caspase-3/7. Activity of caspase3/7 was measured using a luminescent assay. RESULTS: After E2 treatment, more than twofold alteration was observed in 25 upregulated and 10 downregulated miRNAs. Expression of miR-23a in p53-mutated male cell-lines was significantly lower than cell-lines with functional p53 (all P\0.001), but not in female cells. p53 activation increased miR-23a expression in p53 +/+ HepG2 cells (P\0.0001 at 12 h. P\0.01 at 24 h), but not in p53-/-Hep3B cells. E2 via ERa could significantly activated miR- 23a (P\0.001) and p53 (P\0.01) expression, and thus replenished p53-deficiency SNU387 cells in activation of miR-23a. Moreover, miR-23a mimic and E2 significantly activated miR-23a (P\0.001) and suppressed the expression of its target XIAP (P\0.0001 and P\0.01). Decreasing of XIAP contributes to activation of caspase-3 activity and cell apoptosis. Caspase-3 mRNA was significantly upregulated with E2 and miR-23a mimic treatment (P\0.0001 for E2, and P\0.01 for miR-23a mimic). Treatment of cells with anitmiR- 23a increased XIAP expression (P\0.001), and abolished caspase-3 activation (P\0.001). CONCLUSIONS: This study revealed a novel E2-signaling mechanism in regulating miRNAs expression and apoptosis that may contribute to sex difference in HCC development.