Circ-RNF13, as an oncogene, regulates malignant progression of HBV-associated hepatocellular carcinoma cells and HBV expression and replication through circ-RNF13/miR-424-5p/TGIF2 ceRNA pathway

Abstract

The circular RNA RNF13 (circ-RNF13; ID: hsa_circ_0067717) is a novel identified abnormally upregulated circRNA in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) patients. However, its role and mechanism remain to be further annotated. The expression of circ-RNF13, microRNA (miR)-424-5p, and TGFβ-induced factor homeobox 2 (TGIF2) were detected by real-time quantitative PCR and western blotting, and their interaction was confirmed by dual-luciferase reporter assay. Functional assays were performed using MTS assay, colony formation assay, flow cytometry, enzyme-linked immunosorbent assay, transwell assay, and xenograft tumor model, along with real-time quantitative PCR. Circ-RNF13 was upregulated in HBV-infected human HCC tissues and HBV-expressing cells (Huh7-HBV and Hep3B-HBV), accompanied with TGIF2 upregulation and miR-424-5p downregulation. Blocking circ-RNF13 enhanced the apoptosis rate of Huh7-HBV and Hep3B-HBV cells but inhibited cell viability, colony formation, migration, and invasion, along with suppressed tumor growth in vivo. Besides, HBV DNA copies and levels of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) were diminished by circ-RNF13 knockdown in Huh7-HBV and Hep3B-HBV cells. Mechanistically, circ-RNF13 and TGIF2 served as competing endogenous RNAs (ceRNAs) for miR-424-5p. Overexpressing miR-424-5p mimicked and silencing miR-424-5p counteracted the effects of circ-RNF13 depletion in HBV-expressing HCC cells in vitro. Consistently, TGIF2 restoration partially abrogated the role of miR-424-5p upregulation in Huh7-HBV and Hep3B-HBV cells. The circ-RNF13 sponged miR-424-5p to suppress HBV-associated HCC cells malignant progression and HBV infection by regulating TGIF2, providing a novel insight into the occurrence and treatment of HBV-associated HCC.