RNF13 and hepatocellular carcinoma: In vitro cells, circ-RNF13 expression level was higher in HBV-negative HCC cells (Huh7 and Hep3B) than normal THLE-2 cells, and more increased in HBV-expressing HCC cells (Huh7-HBV and Hep3B-HBV) (Figure 1B).