Induction of apoptosis in p53-deficient human hepatoma cell line by wild-type p53 gene transduction: Inhibition by antioxidant

We investigated the role of wild-type (wt)-p53 as an inducer of apoptotic c ell death in human hepatoma cell lines. Following the retrovirus-mediated t ransduction of the wt-p53 gene, Hep3B cells lacking the endogenous p53 expr ession began to die through apoptosis in 4 h. They showed a maximal apoptot ic death at 12 h, whereas HepG2 cells expressing endogenous p53 did not. Ho wever, the transduction of the wt-p53 gene elicited growth suppression of b oth Hep3B and HepG2 cells. P21(WAF1/CIP1), a p53-inducible cell cycle inhib itor, was induced, not only in Hep3B cells undergoing apoptosis, but also i n HepG2 cells. The kinetics of the p21(WAF1/CIP1) induction, DNA fragmentat ion, and growth suppression of the Hep3B cells showed that DNA fragmentatio n and growth suppression progressed rapidly following p21(WAF1/CIP1) accumu lation. N-acetylcysteine or glutathione, potent antioxidants, strongly inhi bited the DNA fragmentation, but did not reduce the elevated level of p21(W AF1/CIP1). These findings suggested that p21(WAF1/CIP1) was not a critical mediator for the execution of p53-mediated apoptosis, although it contribut ed to the growth inhibition of cells undergoing apoptosis. Furthermore, p53 -mediated apoptosis could be repressed by antioxidants.