CCNE2 and hepatocellular carcinoma: In addition, expression analysis of those key genes in HCC tissues compared to normal tissues demonstrated that EXO1, PARP1, H2AX, BRCA1, RAD51, CCNB1, CDK1, CDC25C, and CCNE2 were overexpressed in HCC tissues, further supporting the role of these genes in HCC progression (Figure 2E).