Microarray expression profiles in breast cancer MCF-7 cells following exposure to benzo[a]pyrene and its diol epoxide

Abstract

Maintenance of genome integrity in mammalian cells may be compromised by the concomitant accumulation of DNA damage and loss of repair functions. Polycyclic aromatic hydrocarbons are classic DNA-damaging and tumor-promoting agents. Benzo[a]pyrene (B[a]P), a prototype PAH, induces several genotoxic responses, including cell cycle arrest, oxidative stress and DNA adduct formation. Exposure of MCF-7 cells to B[a]P (1−5 M) and the B[a]P diol epoxide (BPDE) (50−100 nM) induced transient S-phase arrest, which was followed by accumulation in G2 and M and 70% loss of cell viability. In cells treated with B[a]P and BPDE, we observed segregation of nucleolar material and a drastic reduction in the number of ribosomal fibrillar centers. To identify the expression profile in cells treated with B[a]P or BPDE, we analyzed the levels of expression of 1,152 selected genes using a GeneMAP CancerArray in control and treated cells. Changes in gene expression were evaluated twice in duplicate (n=4). Compared with the expression levels in untreated cells, transcripts that were upregulated by both B[a]P and BPDE included members of the cytochrome P450, AP-1 (Fra-1, Fra-2) and glutathione S-transferase families; PARP; and G1/S-specific cyclins. In contrast, transcript levels for BRCA-1, G2/M cyclins, bcl-2, junB and fosB were downregulated in cells treated with B[a]P or BPDE. Treatment with the metabolite BPDE tended to elicit a stronger response than treatment with B[a]P. Analysis of expression profiles by microarray may be useful to understand the interactions among overlapping pathways and assess exposure to environmental carcinogens.