PLK3 and hepatocellular carcinoma: In this study, we observed significant down-regulation in the expression levels of DNA damage response factors such as polo-like kinase 2 (Plk2) and polo-like kinase 3 (Plk3) in the RCLG/Alb-Cre transgenic mouse livers (Figure 6 and Supplementary Table 2) and human HCC tissue samples (Figure 7).