MDM2 and neoplasm: Although we did not clarify the interaction of Δ40p53 with FL-p53 or MDM2, our observations that Δ40p53 increased the protein half-life of FL-p53 and augmented the FL-p53-induced anti-tumor activity suggest that Δ40p53 may positively regulate FL-p53 activity in our proposed HCC cell model.