title: Genetic variation and antioxidant response gene expression in the bronchial airway epithelium of smokers at risk for lung cancer.
abstract: Prior microarray studies of smokers at high risk for lung cancer have demonstrated that heterogeneity in bronchial airway epithelial cell gene expression response to smoking can serve as an early diagnostic biomarker for lung cancer. As a first step in applying functional genomic analysis to population studies, we have examined the relationship between gene expression variation and genetic variation in a central molecular pathway (NRF2-mediated antioxidant response) associated with smoking exposure and lung cancer. We assessed global gene expression in histologically normal airway epithelial cells obtained at bronchoscopy from smokers who developed lung cancer (SC, n = 20), smokers without lung cancer (SNC, n = 24), and never smokers (NS, n = 8). Functional enrichment analysis showed that the NRF2-mediated, antioxidant response element (ARE)-regulated genes, were significantly lower in SC, when compared with expression levels in SNC. Importantly, we found that the expression of MAFG (a binding partner of NRF2) was correlated with the expression of ARE genes, suggesting MAFG levels may limit target gene induction. Bioinformatically we identified single nucleotide polymorphisms (SNPs) in putative ARE genes and to test the impact of genetic variation, we genotyped these putative regulatory SNPs and other tag SNPs in selected NRF2 pathway genes. Sequencing MAFG locus, we identified 30 novel SNPs and two were associated with either gene expression or lung cancer status among smokers. This work demonstrates an analysis approach that integrates bioinformatics pathway and transcription factor binding site analysis with genotype, gene expression and disease status to identify SNPs that may be associated with individual differences in gene expression and/or cancer status in smokers. These polymorphisms might ultimately contribute to lung cancer risk via their effect on the airway gene expression response to tobacco-smoke exposure.
authors.affiliation: Environmental Genomics Section, Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States of America.
authors.forename: Xuting
authors.initials: X
authors.lastname: Wang
authors.forename: Brian N
authors.initials: BN
authors.lastname: Chorley
authors.forename: Gary S
authors.initials: GS
authors.lastname: Pittman
authors.forename: Steven R
authors.initials: SR
authors.lastname: Kleeberger
authors.forename: John
authors.initials: J
authors.lastname: Brothers
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.forename: Avrum
authors.initials: A
authors.lastname: Spira
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Bell
mesh_terms: D000328:Adult; D000368:Aged; D000975:Antioxidants / Q000378:metabolism*; D001665:Binding Sites; D001980:Bronchi / Q000473:pathology*; D045744:Cell Line, Tumor; D020869:Gene Expression Profiling; D056426:Genetic Loci / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D051259:MafG Transcription Factor / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D012097:Repressor Proteins / Q000378:metabolism; D020545:Respiratory Mucosa / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D017422:Sequence Analysis, DNA; D012907:Smoking / Q000235:genetics* / Q000473:pathology
chemical_list: D000975:Antioxidants; C103944:MAFG protein, human; D051259:MafG Transcription Factor; D051267:NF-E2-Related Factor 2; D012097:Repressor Proteins