PCNA and hepatocellular carcinoma: Forced expression of ISX in hepatoma cells (SK-Hep1 and PLC5) significantly increased the expression of proliferation markers (e.g., Cyclin D1, c-Myc, Cdc25A, and PCNA), anti-apoptosis markers (p65 signal related proteins, Bcl-2, and Mcl-1), cell cycle markers like E2F1, and phospho-E2F1 (p-E2F1; serine 332) but not DP1 protein (Figures 3D, 3E and S1A).