E2F1 and hepatocellular carcinoma: P53 inactivation is abundant in HCC even in the absence of TP53 mutations, leading to overexpression of genes normally repressed by p53 such as EZH2, a histone-methyltransferase that epigenetically regulates stem cell maintenance, and CCNB1, E2F1 and FOXM1, all present in our list of strongest prognostic markers [17].