PCNA and hepatocellular carcinoma: Consistently, 3 independent methods of evaluating hepatocyte proliferation—immunostaining for proliferation markers Ki67, proliferating cell nuclear antigen (PCNA), and cytokeratin-19—all showed significantly decreased numbers of proliferating cells in the livers from Stk25-/- mice as opposed to wild-type controls (Figure 3), and this difference was observed both in DEN- and CDAA-induced models of HCC.