MicorRNA-148b inhibits cell proliferation and facilitates cell apoptosis by regulating DNA Methyltransferase 1 in endometrial cancer

BACKGROUND: MicroRNA (miR)-148b has been shown to be dysregulated in a number of cancers; however, studies on the role of miR-148b in the gynaecologic malignancy endometrial cancer (EC) are rare. The purpose of this study was to explore the role of miR-148b in EC and the underlying molecular mechanism. METHODS: The expression levels of miR-148b and DNA methyltransferase 1 (DNMT1) were determined by quantitative real-time PCR (qRT-PCR) in both EC tissues and cell lines (HEC-1A and HEC-1B). These EC cell lines were then transfected with either an miR-148b inhibitor or miR-148b mimics, and cell proliferation, colony, and apoptosis and the cell cycle were measured by the cell counting kit-8, colony formation assay, and flow cytometry assays, respectively. In addition, the expression levels of p16, cyclin-dependent kinase 4 (CDK4), cyclin D1, caspase-3, B-cell lymphoma 2 (Bcl-2), and Bcl-2-associated X (Bax) were assessed by western blotting. Dual luciferase reporter and RNA pull-down assays were performed to investigate the target genes of miR-148b and validate their relationship. RESULTS: miR-148b expression was down-regulated in both EC tissues and HEC-1A and HEC-1B cells, whereas DNMT1 was highly expressed. Moreover, transfection of miR-148b mimics inhibited cell proliferation and cell cycle progression, but induced cell apoptosis. Western blotting showed that transfection of miR-148b mimics markedly increased caspase-3 and cyclin D1 expression, whereas transfection of miR-148b inhibitor dramatically decreased the expression of caspase-3 and cyclin D1. Importantly, we determined that DNMT1 is a target gene of miR-148b in EC cells, and silencing of DNMT1 reversed the effects of miR-148b inhibitor on cell proliferation, cell cycle progression, and apoptosis in EC. CONCLUSIONS: miR-148b inhibits cell proliferation and facilitates cell apoptosis in EC by regulating DNMT1.