TP53 and hepatocellular carcinoma: Mutations involving P53 are frequent and are associated with low P53 function, as evaluated by assessment of P53 transcriptional target expression; however, the low P53 target expression HCC group included also some P53-WT tumors: in these cases, the low P53 expression was ascribed to overexpression by gene amplification of MDM4, a P53 inhibitory protein.