title: AHR- and DNA-damage-mediated gene expression responses induced by benzo(a)pyrene in human cell lines.
abstract: Carcinogens induce complex transcriptional responses in cells that may hold key mechanistic information. Benzo(a)pyrene (BaP) modulation of transcription may occur through the activation of the aryl hydrocarbon receptor (AHR) or through responses to DNA damage. To characterize further the expression profiles induced by BaP in HepG2 and MCF-7 cells obtained in our previous study, they were compared to those induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which activates AHR but does not bind to DNA, and anti-benzo(a)pyrene- trans-7,8-dihydrodiol-9,10-epoxide (BPDE), which binds directly to DNA but does not activate AHR. A total of 22 genes had altered expression in MCF-7 cells after both BaP and TCDD exposure, and a total of 29 genes had altered expression in HepG2 cells. In both cell lines, xenobiotic metabolism was upregulated through induction of NQO1, MGST1, and CYP1B1. A total of 78 expression changes were induced by both BaP and BPDE in MCF-7 cells, and a total of 29 expression changes were induced by both BaP and BPDE in HepG2 cells. These genes were predominantly involved in cell cycle regulation, apoptosis, and DNA repair. BaP and BPDE caused the repression of histone genes in both cell lines, suggesting that regulation of these genes is an important component of the DNA damage response. Interestingly, overlap of the BPDE and TCDD gene expression profiles was also observed. Furthermore, some genes were modulated by BaP but not by TCDD or BPDE, including induction of CRY1 and MAK, which may represent novel signaling pathways that are independent of both AHR activation and DNA damage. Promoter analysis identified candidate genes for direct transcriptional regulation by either AHR or p53. These analyses have further dissected and characterized the complex cellular response to BaP.
authors.affiliation: Section of Molecular Carcinogenesis, The Institute of Cancer Research, Surrey, UK. sarah.hockley@icr.ac.uk
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Hockley
authors.forename: Volker M
authors.initials: VM
authors.lastname: Arlt
authors.forename: Daniel
authors.initials: D
authors.lastname: Brewer
authors.forename: Robert
authors.initials: R
authors.lastname: Te Poele
authors.forename: Paul
authors.initials: P
authors.lastname: Workman
authors.forename: Ian
authors.initials: I
authors.lastname: Giddings
authors.forename: David H
authors.initials: DH
authors.lastname: Phillips
mesh_terms: D001564:Benzo(a)pyrene / Q000378:metabolism / Q000633:toxicity*; D001665:Binding Sites; D002274:Carcinogens, Environmental / Q000378:metabolism / Q000633:toxicity*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D018736:DNA Adducts / Q000378:metabolism*; D004249:DNA Damage; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D002274:Carcinogens, Environmental; D018736:DNA Adducts; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D016159:Tumor Suppressor Protein p53; D001564:Benzo(a)pyrene; D019363:Cytochrome P-450 CYP1A1