Circ_HIPK3 Knockdown Inhibits Cell Proliferation, Migration and Invasion of Cholangiocarcinoma Partly via Mediating the miR-148a-3p/ULK1 Pathway

BACKGROUND: The incidence of cholangiocarcinoma (CCA) is on the rise in recent years, and its pathogenesis may be associated with the deregulation of circular RNAs (circRNAs). Hence, we aimed to investigate the role of circRNA homeodomain interacting protein kinase 3 (circ_HIPK3) in CCA. METHODS: The expression of circ_HIPK3, miR-148a-3p and unc-51 like kinase 3 (ULK1) mRNA was detected using quantitative real-time polymerase chain reaction (qPCR). The role of circ_HIPK3 in cell proliferation was detected by 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide (MTT) assay and colony formation assay. Cell apoptosis and cell cycle progression were investigated using flow cytometry assay. Cell migration and invasion were detected by transwell assay. The protein levels of ULK1 and migration/invasion-associated markers were measured using Western blot. The putative relationship between miR-148a-3p and circ_HIPK3 or ULK1 was validated by dual-luciferase reporter assay. The role of circ_HIPK3 was also investigated in vivo. RESULTS: Circ_HIPK3 was overexpressed in CCA tissues and cells. In function, circ_HIPK3 knockdown inhibited CCA cell proliferation, migration and invasion and induced apoptosis and cycle arrest. It was confirmed that miR-148a-3p was a target of circ_HIPK3, and ULK1 was a target of miR-148a-3p. Circ_HIPK3 regulated ULK1 expression by targeting miR-148a-3p. Rescue experiments showed that miR-148a-3p inhibition reversed the effects of circ_HIPK3 knockdown. Besides, miR-148a-3p enrichment-blocked cell proliferation, migration and invasion were recovered by ULK1 overexpression. In vivo, circ_HIPK3 knockdown inhibited solid tumor growth. CONCLUSION: Circ_HIPK3 knockdown blocked CCA malignant development partly via regulating the miR-148a-3p/ULK1 pathway.