Aberrant DNA methylation is widely observed in various types of cancer, and expression of microRNAs (miRNAs/miRs) is suppressed by DNA methylation. The present study explored tumor suppressor miRNAs downregulated by DNA methylation in endometrial cancer cells, as the basis of a novel therapeutic approach for endometrial cancer. Among 821 candidate miRNAs, miR‑34b was identified as an upregulated miRNA after demethylation treatment in all four endometrial cancer cell lines (HEC‑108, SNG‑II, Ishikawa and HHUA) examined. miR‑34b expression with or without demethylation treatment in cancer cells was confirmed by TaqMan quantitative PCR. MYC and MET, the predicted target genes of miR‑34b, were downregulated at both the RNA and protein levels following miR‑34b overexpression. Following miR‑34b treatment, inhibition of cell growth and invasion, and cell cycle arrest were observed in HEC‑108 cells. Sensitivity to paclitaxel was increased in cancer cells with miR‑34b overexpression, compared with untreated cancer cells, but this difference was not identified for cisplatin or doxorubicin. In vivo, combination treatment with miR‑34b and paclitaxel markedly reduced tumor growth compared with treatment with negative control miRNA and paclitaxel. These data suggest that miR‑34b enhances paclitaxel sensitivity in endometrial cancer cells, and that miR‑34b and MET are key targets for treatment of endometrial cancer. The present results may contribute to the development of combination treatment with a demethylation agent, miR‑34b mimic or MET inhibitor and an anticancer drug.
Keywords: endometrial cancer; microRNA; microRNA-34b; chemosensitivity; paclitaxel.