title: Oxidative stress induces hypomethylation of LINE-1 and hypermethylation of the RUNX3 promoter in a bladder cancer cell line.
abstract: Increased oxidative stress and changes in DNA methylation are frequently detected in bladder cancer patients. We previously demonstrated a relationship between increased oxidative stress and hypomethylation of the transposable long-interspersed nuclear element-1 (LINE-1). Promoter hypermethylation of a tumor suppressor gene, runt-related transcription factor 3 (RUNX3), may also be associated with bladder cancer genesis. In this study, we investigated changes of DNA methylation in LINE-1 and RUNX3 promoter in a bladder cancer cell (UM-UC-3) under oxidative stress conditions, stimulated by challenge with H2O2 for 72 h. Cells were pretreated with an antioxidant, tocopheryl acetate for 1 h to attenuate oxidative stress. Methylation levels of LINE-1 and RUNX3 promoter were measured by combined bisulfite restriction analysis PCR and methylation-specific PCR, respectively. Levels of LINE-1 methylation were significantly decreased in H2O2-treated cells, and reestablished after pretreated with tocopheryl acetate. Methylation of RUNX3 promoter was significantly increased in cells exposed to H2O2. In tocopheryl acetate pretreated cells, it was markedly decreased. In conclusion, hypomethylation of LINE-1 and hypermethylation of RUNX3 promoter in bladder cancer cell line was experimentally induced by reactive oxygen species (ROS). The present findings support the hypothesis that oxidative stress promotes urothelial cell carcinogenesis through modulation of DNA methylation. Our data also imply that mechanistic pathways of ROS-induced alteration of DNA methylation in a repetitive DNA element and a gene promoter might differ.
authors.affiliation: Departments of Biochemistrym, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Wikrom
authors.initials: W
authors.lastname: Wongpaiboonwattana
authors.forename: Piyaratana
authors.initials: P
authors.lastname: Tosukhowong
authors.forename: Thasinas
authors.initials: T
authors.lastname: Dissayabutra
authors.forename: Apiwat
authors.initials: A
authors.lastname: Mutirangura
authors.forename: Chanchai
authors.initials: C
authors.lastname: Boonla
mesh_terms: D050677:Core Binding Factor Alpha 3 Subunit / Q000737:chemistry / Q000235:genetics*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D050050:Protein Carbonylation; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology
chemical_list: D050677:Core Binding Factor Alpha 3 Subunit; D004273:DNA, Neoplasm; D016877:Oxidants; D017382:Reactive Oxygen Species; C493729:Runx3 protein, human; D006861:Hydrogen Peroxide