Carcinogenesis Advance Access originally published online on October 31, 2008
Carcinogenesis 2009 30(1):50-58; doi:10.1093/carcin/bgn249
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Published by Oxford University Press 2008.
Large-scale evaluation of candidate genes identifies associations between DNA repair and genomic maintenance and development of benzene hematotoxicity
Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
1 School of Public Health, University of California, Berkeley, CA 94720, USA
2 Environmental and Occupational Health Division, Utrecht University, Utrecht, The Netherlands
3 Institute of Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention, Beijing, China
* To whom correspondence should be addressed. Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, 6120 Executive Boulevard, Bethesda, MD 20892, USA. Tel: +1 301 435 4706; Fax: +1 301 402 1819; Email: qingl{at}mail.nih.gov
Benzene is an established human hematotoxicant and leukemogen but its mechanism of action is unclear. To investigate the role of single-nucleotide polymorphisms (SNPs) on benzene-induced hematotoxicity, we analyzed 1395 SNPs in 411 genes using an Illumina GoldenGate assay in 250 benzene-exposed workers and 140 unexposed controls. Highly significant findings clustered in five genes (BLM, TP53, RAD51, WDR79 and WRN) that play a critical role in DNA repair and genomic maintenance, and these regions were then further investigated with tagSNPs. One or more SNPs in each gene were associated with highly significant 10–20% reductions (P values ranged from 0.0011 to 0.0002) in the white blood cell (WBC) count among benzene-exposed workers but not controls, with evidence for gene–environment interactions for SNPs in BLM, WRN and RAD51. Further, among workers exposed to benzene, the genotype-associated risk of having a WBC count <4000 cells/µl increased when using individuals with progressively higher WBC counts as the comparison group, with some odds ratios >8-fold. In vitro functional studies revealed that deletion of SGS1 in yeast, equivalent to lacking BLM and WRN function in humans, caused reduced cellular growth in the presence of the toxic benzene metabolite hydroquinone, and knockdown of WRN using specific short hairpin RNA increased susceptibility of human TK6 cells to hydroquinone toxicity. Our findings suggest that SNPs involved in DNA repair and genomic maintenance, with particular clustering in the homologous DNA recombination pathway, play an important role in benzene-induced hematotoxicity.
Abbreviations: FDR, false discovery rate; HR, homologous recombination; ln, natural log; shRNA, short hairpin RNA; SNP, single-nucleotide polymorphism; WBC, white blood cell
Received September 13, 2008; revised October 26, 2008; accepted October 28, 2008.