RRM2 and hepatocellular carcinoma: The survival analysis using univariate Cox analysis was performed for five potential hub genes (TOP2A, RRM2, NEK2, CDK1, and CCNB1) obtained from gene co-expression and PPI networks, and three other genes of the top ten genes with the highest intramodular connectivity (RFC4, PRIM1, and KIF14) in HCC.