| Coke oven emission has been classified as class 1 carcinogens by International Agency for Research on Cancer, that is estabbolished human carcinogens. A lines of epidemiological evidences have shown the etiologic link between carcinogenic PAH exposure and increased risk of lung cancer in coke oven workers. In China, lung cancer of coke oven workers has been classified as one of eight prescribed occupational cancers. Studies showed that genomic instability was the key biological event from PAH exposure to lung cancer development. There are significantly higher levels of chromosome damage in PAH exposed workers than non-PAH exposed workers. The facts that the levels of chromosome damage were different among the similar PAH exposures suggest that individual genetic variation may influence the susceptibility to PAH-induced mutagenesis.In this study, we investigated the relationships between polymorphisms of ataxia-telangiectasia mutated gene (ATM) and the susceptibility of chromosome damage induced by PAH exposure and related molecular mechanism of susceptible difference. The main results are as follows:1. The relationship between polymorphisms of ATM gene and chromosome damage in peripheral blood lymphocytes was detected by cytokinesis-block micronucleus (CBMN) assay among 140 PAH exposed workers and 66 non-PAH exposed workers. Multivariate analysis of covariance with adjustment for urinary 1-OHP, age, sex, smoking status revealed that among coke oven workers, the ATM rs600931 AG genotype carriers exhibited significantly higher CBMN frequency (11.14±6.91%) than did the GG (7.66±5.69‰, P=0.015); AG+AA genotype carriers had significantly higher CBMN frequency than did the GG genotype carriers (P=0.038). For the rs189037 G>A polymorphism, the GA and GA+AA genotype carriers exhibited significantly higher CBMN frequency (10.99±6.90‰and 10.51±6.76‰, respectively) than did the GG genotype carriers (7.72±5.82‰, P=0.018 and 0.035, respectively). For the rs624366 G>C polymorphism, the GC and GC+CC genotype carriers exhibited significantly higher CBMN frequency (11.34±6.74‰and 10.73±6.62‰, respectively) than did the GG genotype carriers (7.61±6.07‰, P=0.001 and 0.003, respectively). The ATM rs227092 GT genotype carriers exhibited significantly higher CBMN frequency (10.78±6.60‰) than did the GG genotype carriers (7.91±6.30‰, P=0.025). The haplotype pairs GGGGTGC/AAACATT exhibited significantly higher CBMN frequency (12.05±7.40%) than did the GGGGTGC/GGGGTGC (7.51±6.19%, P=0.007).2. The difference of chromosome damage induced by B(a)P between siATM cells and control vector (siGFP) cells was investigated by cytokinesis-block micronucleus assay. The results showed that the frequencies of CBMN increased in a dose-dependent tendency in siATM cells and siGFP cells, and the frequencies of CBMN were significantly higher in siATM cells than siGFP cells at 4μM and 8μM B(a)P treatment.The difference of DNA repair capacity (DRC) induced by bleomycin between siATM cells and siGFP cells was assessed by single cell gel electrophoresis assay. The results showed that the DRC was significantly lower in 16HBE-siATM cells (56.66±0.78%) than that in 16HBE-siGFP cells (70.13±3.82%) at 10μg/ml bleolymcin treatment, and HEK-siATM cells had lower DRC (63.86±2.17%) than did HEK-siGFP cells (73.90±1.67%) as well.3. Flow cytometry was used to analyze the changes of cell cycle induced by B(a)P in siATM cells and siGFP cells. The results showed that a decreased G1 phase and an increased G2 phase were observed in 16HBE-siATM cells treated with 4μM B(a)P for 48h, compared with 16HBE-siGFP cells. We also observed a decreased G1 phase and G2 phase in HEK-siATM cells, and along with an increased S phase at 4μM B(a)P treatment for 48h, compared with HEK-siGFP cells. Western-blotting was used to detect the expression of ATM, P53, NBS1 and rH2AX induced by B(a)P for 24h. The results indicated that there were not marked changes of ATM protein expression induced by 8μM B(a)P for 24h in 16HBE-siGFP cells and HEK-siGFP cells, compared with corresponding solvent control group, repectively. Increased expressions of P53, NBS1 and rH2AX were observed in both siATM cells and siGFP cells induced by 8μM B(a)P for 24h, compared with corresponding solvent control group, repectively.4. The difference of reporter gene expression was detected in ATM gene 5'untranslated region (rs189037G>A) variant and 3'untranslated region (rs227092G>T) variant by dual-luciferase reporter gene assay. The results showed that the expression of luciferase was not different between rs189037G and rs189037A in three cell lines including 16HBE, CCC-HPF-1 and MRC-5, and the difference of luciferase expression was not found between rs227092G and rs227092T in these three cell lines, too.In summary, the findings of this study suggested that ATM gene polymorphism might be one of the susceptible factors of chromosome damage induced by polycyclic aromatic hydrocarbons exposure. Additionally, this study confirmed that ATM played an important role in repair of chromosome damage and cell cycle control induced by B(a)P.
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