title: [Hypermethylation of O(6)-methylguanine-DNA methyltransferase in human bronchial epithelial cell induced by organic extracts of coke oven emissions].
abstract: OBJECTIVE
  To elucidate the mechanism of carcinogenesis induced by coke oven emissions by investigating the cell genetic damage index and the methylation of O⁶-methylguanine-DNA methyltransferase (MGMT).
  
  
  METHODS
  The human bronchial epithelial cell 16HBE was treated by 1 µmol/L B(a)P for 48 h, and then was exposed continuously to either 1‰ dimethyl sulfoxide (DMSO) or organic extracts of coke oven emission (OE-COE) for five days at the concentrations of 0, 2.5, 5.0, 10.0 and 20.0 µg/ml. The methylation-specific PCR (MSP-PCR), RT-PCR and immunoblotting were applied to detect the methylation status, changes of mRNA and protein of MGMT, respectively. Single cell gel electrophoresis was used to detect DNA damage induced by OE-COE.
  
  
  RESULTS
  Compared with the control group (DMSO), there was a significant hypermethylation in all study groups, along with the suppression of mRNA and protein in a dose-dependent manner, and the gradation ratio of them was 1.0, 0.96, 0.96, 0.85, 0.32 and 1.0, 1.0, 1.1, 0.41, 0.52, separately. There was a significant DNA damage with a dose-effect relationship in all study groups (F = 41.22, P < 0.05), and the comet Olive tail moment was (2.98 ± 1.43), (4.76 ± 1.79), (10.09 ± 1.75), (11.38 ± 1.77), (11.67 ± 1.88). The further study found that the index of DNA damage was negatively correlated to the expression of MGMT mRNA and its protein.
  
  
  CONCLUSIONS
  The DNA damage induced by COE might be associated with the suppression of MGMT caused by its hypermethylation.
authors.affiliation: Key Lab of Chemical Safety and Health, National Institute of Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention, Beijing 100050, China.
authors.forename: Jun-xiang
authors.initials: JX
authors.lastname: Ma
authors.forename: Hua-wei
authors.initials: HW
authors.lastname: Duan
authors.forename: Chuan-feng
authors.initials: CF
authors.lastname: Huang
authors.forename: Hai-jun
authors.initials: HJ
authors.lastname: Yang
authors.forename: Yu-fei
authors.initials: YF
authors.lastname: Dai
authors.forename: Yong
authors.initials: Y
authors.lastname: Niu
authors.forename: Ping
authors.initials: P
authors.lastname: Bin
authors.forename: Qing
authors.initials: Q
authors.lastname: Liu
authors.forename: Yu-xin
authors.initials: YX
authors.lastname: Zheng
mesh_terms: D001980:Bronchi / Q000166:cytology; D002460:Cell Line; D003077:Coke / Q000009:adverse effects*; D020552:Comet Assay; D004249:DNA Damage; D019175:DNA Methylation; D004260:DNA Repair; D004847:Epithelial Cells / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics / Q000378:metabolism*
chemical_list: D003077:Coke; D019853:O(6)-Methylguanine-DNA Methyltransferase