Epigenetic Silencing of MiR-130b in Ovarian Cancer Promotes the Development of Multidrug Resistance by Targeting Colony-stimulating Factor 1

Objective: The purpose of this study was to investigate the role of miR-130b in the development of multidrug-resistant ovarian cancer.

Methods: The expression of miR-130b was assessed in ovarian tissues and cell lines by qRT-PCR. In vitro, miR-130b level was manipulated by transfection with mimics or inhibitors. Methylation level of miR-130b was evaluated by quantitative methylation-specific PCR (qMSP). CSF-1 expression in ovarian tissues and cells was determined by qRT-PCR, immunohistochemistry and ELISA, respectively. CSF-1 regulated by miR-130b was detected using Dual Luciferase Reporter system.

Results: Down-regulation of miR-130b in ovarian cancer was associated with FIGO III-IV clinical stages and poorer histological differentiation. MiR-130b was downregulated in multidrug resistant ovarian cancer cells. Restoration of miR-130b expression could sensitize these cells to anticancer drugs. MiR-130b hypermethylation was found in ovarian cancer tissues as well as in drug resistant cell lines and the methylation level was negatively correlated with its expression. Demethylation with 5-aza-CdR led to reactivation of miR-130b expression in drug resistant ovarian cancer cell lines concomitant with increase of sensibility to cisplatin and taxol. CSF-1 expression was negatively associated with miR-130b level in ovarian tissues and cell lines. Luciferase assay validated CSF-1 is a direct target of miR-130b. Knock-down of CSF-1 sensitized ovarian cancer cells to anticancer drugs and could partially attenuate the resistance inducing effect of miR-130b inhibitors.

Conclusions: Downregulation of miR-130b promotes the development of multidrug resistant ovarian cancer partially by targeting the 3'-UTR of CSF-1, and the silencing of miR-130b may be mediated by DNA methylation.