Carcinogenesis Advance Access originally published online on October 17, 2007
Carcinogenesis 2008 29(1):202-210; doi:10.1093/carcin/bgm227
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Identification through microarray gene expression analysis of cellular responses to benzo(a)pyrene and its diol-epoxide that are dependent or independent of p53
1 Section of Molecular Carcinogenesis, The Institute of Cancer Research, Brookes Lawley Building, Cotswold Road, Sutton, Surrey SM2 5NG, UK
2 Institute of Food Technology and Food Chemistry, Technical University of Berlin, TIB 4/3-1, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany
3 Cancer Research UK DNA Microarray Facility, The Institute of Cancer Research, Cotswold Road, Sutton, Surrey SM2 5NG, UK
* To whom correspondence should be addressed. Tel: +44 208 722 4259; Fax: +44 208 722 4266;Email: sarah.hockley{at}icr.ac.uk
Human colon carcinoma cells (HCT116) differing in p53 status were exposed to benzo(a)pyrene (BaP) or anti-benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (BPDE) and their gene expression responses compared by complementary DNA microarray technology. Exposure of cells to BPDE for up to 24 h resulted in gene expression profiles more distinguishable by duration of exposure than by p53 status, although a subset of genes were identified that had significantly different expression in p53 wild-type (WT) cells relative to p53-null cells. Apoptotic signalling genes were up-regulated in p53-WT cells but not in p53-null cells and, consistent with this, reduced viability and caspase activity were also p53 dependent. BPDE modulated cell cycle and histone genes in both cell lines and, in agreement with this, both cell lines accumulated in S phase. In p53-WT cells, G2 arrest was also evident, which was associated with accumulation of CDKN1A. Regardless of p53 status, exposure to BaP for up to 48 h had subtle effects on gene transcription and had no influence on cell viability or cell cycle. Interestingly, DNA adduct formation after BaP, but not BPDE, exposure was p53 dependent with 10-fold lower levels detected in p53-null cells. Other cell lines were investigated for BaP–DNA adduct formation and in these the effect of p53 knockdown was also to reduce adduct formation. Taken together, these results give further insight into the role of p53 in the response of human cells to BaP and BPDE and suggest that loss of this tumour suppressor can influence the metabolic activation of BaP.
Abbreviations: BaP, benzo(a)pyrene; BPDE, anti-benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide; cDNA, complementary DNA; CYP, cytochrome P450; DMSO, dimethyl sulfoxide; 3-NBA, 3-nitrobenzanthrone; PAH, polycyclic aromatic hydrocarbon; RTqPCR, real-time quantitative polymerase chain reaction; siRNA, small interference RNA; TNFR, tumour necrosis factor receptor; WT, wild-type
Received April 30, 2007; revised October 3, 2007; accepted October 5, 2007.