miR-191 Inhibition Induces Apoptosis Through Reactivating Secreted Frizzled-Related Protein-1 in Cholangiocarcinoma

Background/Aims: Cholangiocarcinoma (CCA) is one of the most common malignant tumors of the biliary tract originating from biliary epithelial cells. Although many therapeutic strategies have been developed to treat CCA, the survival rate for CCA patients is still quite low. Thus it is urgent to elucidate the pathogenesis of CCA and to explore novel therapeutic targets. miR-191 has been shown to be associated with many human solid cancers, but the function of miR-191 in CCA is still poorly understood. Methods: We first investigated the expression level of miR-191 in human CCA tissues and cell lines with quantitative real-time PCR (qRT-PCR). The effects of miR-191 on CCA cells were determined by Cell Counting Kit-8 assay, colony formation assay and acridine orange/ethidium bromide staining. Finally, we utilized qRT-PCR, western blot and luciferase reporter assays to verify the miR-191 target gene. Results: We showed that miR-191 was up-regulated in CCA cell lines and patients. Knockdown of miR-191 by transfection of its inhibitor sequence blocked RBE cells viability and induced apoptosis of RBE cells. Both qRT-PCR and western blot analysis showed that the secreted frizzled-related protein-1 (sFRP1) level was negatively correlated with that of miR-191. Luciferase assay validated that sFRP1 was a direct target of miR-191. Moreover, knockdown of miR-191 led to suppression of Wnt/β-catenin signaling activation. Co-transfection of sFRP1 small interfering RNA (siRNA) and miR-191 inhibitor re-activated the Wnt/β-catenin signaling pathway as detected by an increased level of β-catenin and phosphorylation of GSK-3β, and restored the expression of survivin and c-myc in RBE cells. Co-transfection of sFRP1 siRNA with miR-191 inhibitor restored the colony formation ability and viability of RBE cells. Conclusion: Taken together, our results demonstrate a novel insight into miR-191 biological function in CCA. Our findings suggest that miR-191 is a potential therapeutic target of CCA treatment.