CDK1 and hepatocellular carcinoma: Based on the data from TCGA project, correlation analysis revealed that PCNA expression was positively associated with the expression of CDC25C (R = 0.68), CDK1 (R = 0.73), CCNB1 (R = 0.67), CCNE2 (R = 0.66), CDC25A (R = 0.62), and CDK2 (R = 0.75) in HCC tissues (Figure 4K; Supplementary Figure 2B).