CCNA2 and hepatocellular carcinoma: Obviously, the protein expression levels of FOXM1, AURKA, CCNA2, MKI67, EZH2, CDC6, CDK1, CCNB1, and TOP2A were not observed or low in normal liver tissues, but medium or high expression levels of these hub genes were detected in HCC tissues (see Fig. S2, Supplemental Digital Content, which demonstrates protein expression levels of these hub genes in HCC).