Association Of Polymorphisms In AKR1C3, ERCC1, XPC With DNA Damage In Peripheral Lymphocytes Of Coke Oven Workers

Coke oven workers are exposed to polycyclic aromatic hydrocarbons (PAH). Epidemiological studies have shown an increase in cancer incidence among workers exposed to PAH, especially for the risk of developing lung cancer. In the exposure-to-disease pathogenic pathway, biomarkers that can provide information of exposure to carcinogenic agents (biomarkers of exposure) and early changes caused by the agents (biomarkers of effect) are needed in epidemiological studies of cancer risk. The albumin adducts are thought to be biologically effective-dose biomarkers of PAH. DNA damage (adducts and strand breaks) represents an early, detectable and critical step in the chemical carcinogenesis process and thus, may serve as an internal dosimeter for carcinogens. A wide variety of non-bulky base damage and single-strand breaks are formed during metabolic activation of PAH and involved in PAH carcinogenesis, and these types of DNA damage can be detected by comet assay and used as a marker of early biological effects of DNA-damaging agents in the living environments and occupational workplaces. To our knowledge, there was no reported investigation on the correlation between BPDE-Alb adduct concentrations and DNA damage in lymphocytes in coke oven workers, although these two biomarkers were individually applied in some occupational biomonitoring. Therefore, we further assessed whether occupational exposure to COEs resulted in high concentrations of BPDE-Alb adducts and DNA damage and their possible correlation in coke oven workers exposed to COEs.It became very clear that genetic predisposition may affect individual susceptibility to carcinogen-induced cancer and carcinogen-induced biomarkers of exposure and effect. Genetic susceptibility can be due to variation in genes for carcinogen metabolizing enzymes and in genes for repair enzymes. The carcinogenicity induced by PAH compounds is believed to be initiated by DNA damage. An increasing number of evidences demonstrate the involvement of reactive oxygen species (ROS) in the production of cancers by PAH. These oxygen species may lead to the formation of oxidative DNA damage. A wide variety of non-bulky base damage and single-strand breaks are formed during metabolic activation of PAH and involved in PAH carcinogenesis. Repair of DNA damage is under genetic control, and DNA repair genes may play a key role in maintaining genome integrity and preventing cancer development. Polymorphisms in DNA repair genes resulting in variation of DNA repair efficiency may therefore be associated with cancer risk. It is generally assumed that bulky DNA adducts, such as those induced by PAH, are repaired by the nucleotide excision repair pathway. XPC is essential in the initial step of damage recognition. ERCC1 in association with the XPF protein incises DNA on the 5' side of the damaged site. The present study evaluated the influence of four polymorphisms of NER genes, together with DNA damage levels detected by comet assay of coke oven workers occupationally exposed to PAH. Our aim was to find potential susceptibility factors on a genetic basis capable of modulating individual responses to PAH genotoxic exposure and the consequent risk of cancer in coke oven workers. Part I Study design and airborne carcinogenic PAH monitoringIn this study, we recruited 232 male workers exposed to COEs and 127 controls not exposed to COEs in the same steel plant in northern China. Prior to blood sampling, a questionnaire to elicit the workplace description, smoking habits, medical history, age and diet was performed for each exposed worker. Questionnaires were completed in a personal interview. The distribution of age, worktime, and smoking and drinking status was similar between coke oven workers and controls. We selected four working sites for exposed group and three working sites for control group. Quantitative chemical analysis of eight carcinogenic PAH (benzo(a)pyrene (B[a]P), benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, dibenz[a,h]anthracene, benzo[g,h,i] perylene, indeno[1,2,3-cd]pyrene) were performed by high performance liquid chromatography with fluorescence detectors according to the methods 5506 published by the National Institute for Occupational Safety and Health. The results of airborne monitoring showed that the median value of the sum of eight carcinogenic PAH in the air of the work places was significantly higher than the control group (P<0.01). The airborne median level of B[a]P alone was significantly higher than the control group (P<0.05).Part II Association between plasma BPDE-Alb adduct concentrations and DNA damage of peripheral blood lymphocytes among coke oven workersCoke oven emissions containing PAH can induce both protein and DNA adducts, such as benzo[a]pyrene-r-7, t-8, t-9,c-10-tetrahydotetrol-albumin (BPDE-Alb) adducts and BPDE-DNA adducts. However, the relationship between these biomarkers for early biological effects is not well documented in coke oven workers. We measured BPDE-Alb adduct concentrations in plasma with reverse-phase high-performance liquid chromatography and DNA damage in peripheral blood lymphocytes with alkaline comet assay. Our results showed that the levels of BPDE-Alb adducts and the Olive tail moment (Olive TM) in exposed group were significantly higher than that in control group (P<0.05). Multivariate logistic regression analysis revealed that the odds ratio (OR) for BPDE-Alb adduct and Olive TM associated with the exposure were 1.72 and 1.96, respectively. Our results showed that there were significant correlations between the concentrations of BPDE-Alb adduct and Olive TM levels in exposed group (r_s=0.235, P<0.01) but not in control group (r_s=0.093, P>0.05). In conclusions, the relationships between biomarkers of biological effective and early biological effects were significantly among coke oven workers..Part III Association of AKR1C3 polymorphisms and DNA damage in peripheral lymphocytes of coke oven workersAKR1C3 is a member of the aldo-keto reductases (AKRs) superfamily, and has been shown experimentally to produce PAH metabolites that form DNA adducts or reactive oxygen species (ROS) leading to oxidative DNA damage. AKR1C3 is a particularly important enzyme in metabolizing potent trana-dihydrodiols containing more than two rings. SNPs in the AKR1C3 gene itself have not yet been examined for their influence on levels of DNA damage in an epidemiology study. We suggested that SNPs in the oxidative stress related-genes AKR1C3 may play a role in the repair of oxidative damage in coke oven workers. DNA damage was detected by alkaline comet assay. The polymorphism of AKR1C3 was analyzed using the ABI Prism 7900 sequence detection system. Data were analyzed using Allelic Discrimination Program. Our results showed that the DNA damage levels of AKR1C3-His/His+His/Gln genotype were higher than the AKR1C3-Gln/Gln genotype among coke oven workers.Part IV Association of ERCC1 and XPC polymorphisms and DNA damage in peripheral lymphocytes of coke oven workersTo investigate the association of polymorphisms of DNA repair enzyme genes and DNA damage in peripheral lymphocytes in coke oven workers, DNA damage was detected using alkaline comet assay and the polymorphisms were analyzed using the ABI Prism 7900 sequence detector. Data were analyzed using Allelic Discrimination Program. Our results showed that the coke oven workers with ERCC1-rs2298881 C/C genotype had higher levels of DNA damage levels compared with ERCC1-rs2298881 A/A+ A/C genotype carriers (P<0.05). ERCC1-rs3212948, XPC-rs2607775 and XPC-rs3729587 polymorphisms were not associated with DNA damage levels (P>0.05). Our results suggest that the coke oven workers with ERCC1-rs2298881 C/C genotype may be susceptible to DNA damage.We further analyzed the correlations of DNA damage levels in peripheral lymphocytes to the hapolotypes of two ERCC1 SNPs. Results showed that the DNA damage levels in workers with ERCC1-CC/GC and CA/CA haplotype pairs was higher than those with ERCC1-CC/GA haplotype pairs(P<0.05) only in coke oven workers, however, there were no significant associations of the DNA damage levels and haplotype pairs (P>0.05) in coke oven workers and controls. The results suggested that there was difference of the DNA damage levels in the coke oven workers with some genotypes or haplotypes in ERCC1 gene, however, these relationships among these genotypes, haplotypes, DNA damage and repair warrant further investigation.