Down-regulation of USP39 impairs cell cycle progression of SMMC-7721 cells. (A) Representative graphs of flow cytometry analysis of SMMC-7721 cell cycle using PI staining. (B) Statistic analysis of percentages of SMMC-7721 cells at different cell cycle stages (G0/G1, S and G2/M). (C) Statistic analysis of percentages of sub-G1 SMMC-7721 cells. ***, P < 0.001.