title: Reactive oxygen species induce epigenetic instability through the formation of 8-hydroxydeoxyguanosine in human hepatocarcinogenesis.
abstract: Chronic hepatitis C (CHC) triggers oxidative stress and contributes to the emergence of hepatocellular carcinoma (HCC). We previously reported that tumor suppressor gene (TSG) methylation is a critical factor during the early stages of hepatocarcinogenesis. In this study, we clarify the association between oxidative stress and epigenetic alterations during hepatocarcinogenesis. We examined DNA oxidation and methylation profiles in 128 liver biopsy samples from CHC patients. The DNA oxidation and methylated TSG numbers were quantified using immunohistochemical analysis of 8-hydroxydeoxyguanosine (8-OHdG) and quantitative PCR for 11 TSGs, respectively. The quantitative chromatin immunoprecipitation-PCR (ChIP-qPCR) assay in HepG2 and fetal liver Hc cells treated with H2O2 was used to quantify trimethyl-H3K4, acetylated-H4K16 (an active chromatin marker), trimethyl-H3K27 (a repressive chromatin marker) and 8-OHdG. We analyzed 30 promoters of 25 different TSGs by qPCR. The high levels of 8-OHdG was the only variable that was significantly associated with the increased number of methylated TSGs in CHC (p < 0.0001). The ChIP-qPCR revealed that after H2O2 treatment of the cell lines, the 8-OHdG-bound promoters showed a modification from an active chromatin (trimethyl-H3K4 and acetylated-H4K16 dominant) to a repressive chromatin (trimethyl-H3K27 dominant) status. We conclude that oxidative stress alters the chromatin status, which leads to abnormal methylation of TSGs, and contributes to hepatocarcinogenesis in CHC patients.
authors.affiliation: Department of Gastroenterology and Hepatology, Kinki University School of Medicine, Osakasayama, Japan.
authors.forename: Naoshi
authors.initials: N
authors.lastname: Nishida
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Arizumi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takita
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kitai
authors.forename: Norihisa
authors.initials: N
authors.lastname: Yada
authors.forename: Satoru
authors.initials: S
authors.lastname: Hagiwara
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Inoue
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Minami
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Ueshima
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Sakurai
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kudo
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D063646:Carcinogenesis / Q000235:genetics* / Q000473:pathology; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D047369:Chromatin Immunoprecipitation; D043171:Chromosomal Instability / Q000187:drug effects; D004249:DNA Damage; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D044127:Epigenesis, Genetic / Q000187:drug effects; D005260:Female; D016147:Genes, Tumor Suppressor; D006657:Histones / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007150:Immunohistochemistry; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D006657:Histones; D017382:Reactive Oxygen Species; D000080242:8-Hydroxy-2'-Deoxyguanosine; D006861:Hydrogen Peroxide; D003849:Deoxyguanosine