title: Oxidative stress indicated by elevated expression of Nrf2 and 8-OHdG promotes hepatocellular carcinoma progression.
abstract: Reactive oxygen species (ROS) is excessively generated in tumors creating an oxidative stress in tumor microenvironment. We investigated hepatic expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and 8-hydroxydeoxyguanosine (8-OHdG) in hepatocellular carcinoma (HCC) patients, and asked if ROS epigenetically upregulated Nrf2 and enhanced aggressiveness in HCC cells. Expression of Nrf2 (n = 100) and 8-OHdG (n = 53) was remarkably increased in HCC tissues compared with the noncancerous hepatic tissues. Elevated expression of 8-OHdG was associated with poor survival in HCC patients. H2O2, as ROS representative, provoked oxidative stress in HepG2 cells, indicated by increased protein carbonyl content and decreased total antioxidant capacity. Nrf2 expression and 8-OHdG formation were markedly increased in the H2O2-treated cells compared with the untreated control. Co-treatment with antioxidants, tocopheryl acetate (TA) and S-adenosylmethionine (SAM) effectively attenuated expression of Nrf2 and 8-OHdG in H2O2-treated cells. HepG2 cells treated with H2O2had significantly higher migration and invasion capabilities than the untreated control cells, and this aggressiveness was significantly inhibited by TA and SAM. Bisulfite sequencing revealed that CpG dinucleotides in Nrf2 promoter were unmethylated in the H2O2-treated cells similar to the untreated control. In conclusion, robust histological evidence of increased antioxidative response and oxidative DNA damage in human HCC tissues was demonstrated. Elevated oxidative DNA lesion 8-OHdG was associated with shorter survival. Experimentally, ROS enhanced Nrf2 expression, 8-OHdG formation and tumor progression in HCC cells. These effects were inhibited by antioxidants. Therefore, oxidative stress-reducing regimens might be beneficial to diminish the ROS-induced HCC progression.
authors.affiliation: Departments of Biochemistry, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Bangkok, 10300, Thailand.
authors.forename: Chakriwong
authors.initials: C
authors.lastname: Ma-On
authors.affiliation: Departments of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Anapat
authors.initials: A
authors.lastname: Sanpavat
authors.affiliation: Departments of Biochemistry, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Bangkok, 10300, Thailand.
authors.forename: Patcharawalai
authors.initials: P
authors.lastname: Whongsiri
authors.affiliation: Departments of Biochemistry, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Bangkok, 10300, Thailand.
authors.forename: Surasit
authors.initials: S
authors.lastname: Suwannasin
authors.affiliation: Center of Excellence in Immunology and Immune-mediated Diseases, Departments of Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Nattiya
authors.initials: N
authors.lastname: Hirankarn
authors.affiliation: Departments of Biochemistry, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Bangkok, 10300, Thailand.
authors.forename: Pisit
authors.initials: P
authors.lastname: Tangkijvanich
authors.affiliation: Departments of Biochemistry, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Bangkok, 10300, Thailand. chanchai.b@chula.ac.th.
authors.forename: Chanchai
authors.identifier: http://orcid.org/0000-0002-6515-4321
authors.initials: C
authors.lastname: Boonla
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D018450:Disease Progression; D005260:Female; D056945:Hep G2 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D051267:NF-E2-Related Factor 2 / Q000096:biosynthesis* / Q000235:genetics; D018384:Oxidative Stress / Q000502:physiology*; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D017382:Reactive Oxygen Species; D000080242:8-Hydroxy-2'-Deoxyguanosine; D006861:Hydrogen Peroxide; D003849:Deoxyguanosine
keywords: 8-OHdG; Cancer progression; Epigenetic; HCC; Nrf2; ROS