Relationship of dibenzo[a,l]pyrene-DNA binding to the induction of p53, p21(WAF1) and cell cycle arrest in human cells in culture

The tumor suppressor protein p53 plays an important role in recognition of DNA damage and induction of subsequent cell cycle arrest. One of its target genes encodes the p21(WAF1) protein which is involved in the mediation of growth arrest after DNA damage has occured. The exceptionally potent carcin o-genic polycyclic aromatic hydrocarbon (PAH) dibenzo[a,l]pyrene (DB[a,l]P) and its ultimate metabolites, the fjord region (+)-syn- and (-)-anti-11,12 -diol 13,14-epoxides (DB[a,l]PDE), were used in order to investigate DNA da mage via adduct formation, subsequent induction of p53 and p21(WAF1), and c ell growth behavior in human mammary carcinoma MCF-7 cells. Exposure of MCF -7 cells to 0.005 mu M DB[a,l]P caused a total DNA binding of 25 pmol adduc ts/mg DNA (48 hrs after treatment) and a significant increase in the level of p53 (12-72 hrs after treatment). 48 hrs after exposure an increased amou nt of the p21(WAF1) protein was detected and its level remained elevated fo r the time measured (168 hrs). Treatment of the cells with (+)-syn- and (-) -anti-DB[a,l]PDE also increased p53 levels. However, the concentration need ed and the binding level observed were in the range of 0.02-0.03 mu M [9-14 pmol (+)-syn-DB[a,l]PDE-DNA adducts/mg] and 0.01 mu M [21 pmol (-)-anti-DB [a,l]PDE-DNA adducts/mg], respectively. Cell cycle studies after exposure t o the parent PAH indicate an arrest of the DNA-damaged cells with accumulat ion in G2.