Abstract
Global hypomethylation, gene-specific methylation, and genome instability are common events in tumorigenesis. To date, few studies have examined the aberrant DNA methylation patterns in coke oven workers, who are highly at risk of lung cancer by occupational exposure to polycyclic aromatic hydrocarbons (PAHs). We recruited 82 PAH-exposed workers and 62 unexposed controls, assessed exposure levels by urinary 1-hydroxypyrene, and measured genetic damages by comet assay, bleomycin sensitivity, and micronucleus assay. The PAHs in coke oven emissions (COE) were estimated based on toxic equivalency factors. We used bisulfite-PCR pyrosequencing to quantitate DNA methylation in long interspersed nuclear element-1 (LINE-1) and O6-methylguanine-DNA methyltransferase (MGMT). Further, the methylation alteration was also investigated in COE-treated human bronchial epithelial (16HBE) cells. We found there are higher levels of PAHs in COE. Among PAH-exposed workers, LINE-1 and MGMT methylation levels (with CpG site specificity) were significantly lowered. LINE-1, MGMT, and its hot CpG site-specific methylation were negatively correlated with urinary 1-hydroxypyrene levels (r = −0.329, p < 0.001; r = −0.164, p = 0.049 and r = −0.176, p = 0.034, respectively). In addition, LINE-1 methylation was inversely associated with comet tail moment and micronucleus frequency, and a significant increase of micronucleus in low MGMT methylation group. In vitro study revealed that treatment of COE in 16HBE cells resulted in higher production of BPDE-DNA adducts, LINE-1 hypomethylation, hypomethylation, and suppression of MGMT expression. These findings suggest hypomethylation of LINE-1 and MGMT promoter could be used as markers for PAHs exposure and merit further investigation.
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Acknowledgments
This research was supported by the National Natural Science Foundation of China (NSFC 81172642, 81130050, 30700659, 81072284), a Key Program of Scientific Research of Public Welfare Project of the Ministry of Health of China (No.200902006), a Distinguished Young Scholar of NSFC (30925029), a National High-Tech Research and Development Program of China (2012AA062804), and partly financed by the State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences (KF2010-02).
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Huawei Duan, Zhini He, and Junxiang Ma contributed equally to this work.
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Duan, H., He, Z., Ma, J. et al. Global and MGMT promoter hypomethylation independently associated with genomic instability of lymphocytes in subjects exposed to high-dose polycyclic aromatic hydrocarbon. Arch Toxicol 87, 2013–2022 (2013). https://doi.org/10.1007/s00204-013-1046-0
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DOI: https://doi.org/10.1007/s00204-013-1046-0