Inhibition of cell death in human mammary epithelial cells by the cooked meat-derived carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mammary bland c arcinogen present in the human diet in cooked meat. To examine if PhIP and its reactive metabolite N-hydroxy-PhIP inhibit apoptosis in human mammary e pithelial MCF-10A cells, confluent cultures deprived of serum and growth fa ctors were incubated for 24 h with either compound. The percentages of dead cells (mean +/- SEM n = 3) as measured by trypan blue exclusion were 5.7 /- 0.6, 3.4 +/- 0.3, 2.7 +/- 0.3, and 0.2 +/- 0.003%, in control, 1 mu M N- hydroxy-PhIP-, 5 mu M N-hydroxy-PhIP-, and 100 mu M PhIP-treated dishes, re spectively. The expression of Bcl-2 and Bcl-x(L) as quantitated by Western blotting was 1.2- to 1.9-fold higher in the treated groups. PhIP-DNA adduct s induced by N-hydroxy-PhIP in MCF-10A cells measured by the P-32-postlabel ing assay were low (<1 x 10(7), relative adduct labeling). No adducts were detected after incubation with PhIP. Western blot analysis indicated that P hIP increased ERK2 phosphorylation concomitant with Bcl-2. The results sugg est that the inhibition of cell death in mammary epithelial cells by PhIP o ccurs independently of PhIP-DNA adducts and may involve enhanced signaling through the MAP kinase pathways. (C) 1999 Academic Press.