PLK1 and hepatocellular carcinoma: As shown in Fig. 6B, D, F, and H, compared to the normal group, the expressions of CCNB1 (P = 3.291E-08), CDK4 (P = 5.258E-06), CDK1 (P = 3.744E-39), and PLK1 (P = 4.172E-04) proteins were upregulated in HCC patients.