TP53 and hepatocellular carcinoma: The role of p53 in the activation of Siah-1 expression by HBx and H2O2 in human hepatoma cells was confirmed by both p53 knockdown and p53 overexpression, which resulted in a decrease in Siah-1 levels in HepG2 cells and an increase in Siah-1 levels in Hep3B cells, respectively (Figure 4c,d).