Adenovirus-mediated wild-type-p53-gene expression sensitizes TNF-resistanttumor cells to TNF-induced cytotoxicity by altering the cellular redox state

We have shown that the loss of p53 function contributed to resistance of tu mor cells to TNF-induced cytotoxicity. In the present study, we evaluated t he effect of wild-type p53 (wt-p53) expression on TNF sensitivity, by intro ducing wt-p53 into MCF7/Adr cells in which p53 was deleted, via a recombina nt adenovirus encoding p53 (Ad-p53), Our results indicate that infection wi th Ad-p53 (50-100 viral particles per cell) resulted in pronounced cytotoxi city, whereas infection with 10 viral particles per cell, which was weakly toxic for the MCF7/Adr cells, sensitized these cells to TNF-induced cell de ath. Moreover, expression of wt-p53 in MCF7/Adr cells induced the productio n of reactive oxygen intermediates (ROIs) and caused glutathione (GSH) depl etion, indicating disturbances in the cellular redox state. Additional trea tment of cells with the anti-oxidant and glutathione (GSH) precursor N-acet ylcysteine (NAC) resulted in inhibition of p53-induced ROIs production and in partial restoration of intracellular GSH levels, which was associated wi th the ability of NAC to inhibit p53-modulated TNF-induced cytotoxicity. In terestingly, Ad-p53 was able to inhibit TNF-induced MnSOD mRNA expression i n MCF7/Adr cells, which might contribute to the sensitization of cells to t he cytotoxic action of TNF, Taken together, our data strongly suggest that wt-p53 expression sensitizes TNF-resistant MCF7 cells with p53 deletion to TNF-induced cell death by a pathway that is dependent on ROIs production. ( C) 2000 Wiley-Liss, Inc.