MiR-222-3p induced by hepatitis B virus promotes the proliferation and inhibits apoptosis in hepatocellular carcinoma by upregulating THBS1

This study aimed to explore the role of miR-222-3p in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). MiR-222-3p expression in tumor tissues of HBV (+) or HBV (-) HCC patients and corresponding cell lines was detected by quantitative reverse transcription PCR (qRT-PCR). Cell proliferation was assessed by cell counting kit-8 (CCK-8) and colony formation assays. Cell apoptosis was evaluated by flow cytometry. The potential targets of miR-222-3p were predicted by Targetscan, and the binding relationship between miR-222-3p and thrombospondin-1 (THBS1) was determined by luciferase reporter assay and RNA immunoprecipitation (RIP) assay. MiR-222-3p was significantly upregulated in HCC tissues and cell lines and further elevated by HBV infection. MiR-222-3p downregulation effectively inhibited the proliferation and induced the apoptosis of HBV (-) HepG2 cells, HBV (+) HepG2.2.15 cells, Huh7-V cells, and Huh7-HBV cells. In addition, miR-222-3p overexpression enhanced the proliferation of these cell lines but exhibited no obvious effect on their apoptosis. Mechanistically, miR-222-3p was directly bound to the 3'-UTR of THBS1 and acted as its competing endogenous RNA (ceRNA). Interestingly, THBS1 silencing attenuated the inhibitory effect of miR-222-3p downregulation on the proliferation of these cell lines in vitro. Our results revealed that HBV infection further increased miR-222-3p expression and promoted HCC progression via miR-222-3p-mediated THBS1 downregulation. Our findings suggest that miR-222-3p might be a potential diagnostic and therapeutic target for HCC and HBV-related HCC.