Modulation of (+/-)-anti-BPDE mediated p53 accumulation by inhibitors of protein kinase C and poly(ADP-ribose) polymerase.

The rapid accumulation of the p53 gene product is considered to be an important component of the cellular response to a variety of genotoxins. In order to gain insights on the biochemical pathways leading to p53 stabilization, the effect of (+/-) 7,8-dihydroxy-anti-9, 10-epoxy-7,8,9,10-tetrahydrobenzo(a)-pyrene [(+/-)-anti-BPDE] induced DNA damage on p53 protein levels was investigated in various repair-proficient and repair-deficient human cells. Brief exposure of normal human fibroblasts to 0.05-1 microM (+/-)-anti-BPDE resulted in elevated p53 protein levels as compared to the constitutive levels of control cells. The rapid induction response, detectable within a few hours, was sustained up to a period of at least 24 h. Repair-proficient and repair-deficient (XPA) human lymphoblastoid cells showed a similar response. The poly(ADP-ribose) polymerase inhibitor, 3-aminobenzamide (3-AB), diminished the p53 induction response by concomitantly decreasing the extent of (+/-)-anti-BPDE induced DNA damage in cells pretreated with the inhibitor. However, the direct involvement of poly ADP-ribosylation was also apparent as 3-AB was able to attenuate (approximately 50%) the p53 response by post-damage inhibitor treatment of the cells. Inhibition of cellular DNA replication by hydroxyurea and AraC, in the presence or absence of DNA damage, also resulted in rapid p53 accumulation in repair-deficient cells. On the contrary, inhibition of protein kinase C (PKC) by calphostin-C led to an abrogation of (+/-)-anti-BPDE mediated p53 induction. Analysis of the downstream effects of carcinogen treatment showed that the lymphoblastoid cells undergo DNA fragmentation indicative of apoptosis while fibroblasts exhibit cell cycle arrest at the G1-S boundary.