TP53 and hepatocellular carcinoma: ASS1 overexpression did not alter p53 or p21 expression in p53 wild-type HCC cells (Fa2N-4 and HepG2), as well as CHOP and phospho-histone H2AX (γ-H2AX) expression also did not change by ASS1 expression in p53 wild-type HCC cells (Fig. 6d).