USP39 and hepatocellular carcinoma: To verify the significance of the above cellular and molecular experimental findings on HCC cell proliferation in vivo and in vitro, the CCK8 assays and plate cloning assays were performed in HCC cell lines, and the resuls showed that DNAAF5 overexpression promoted the proliferation of tumor cells in vitro, whereas USP39 knockdown inhibited this effect (Figures 5E, F).