title: Global analysis of DNA methylation in early-stage liver fibrosis.
abstract: BACKGROUND
  Liver fibrosis is caused by chemicals or viral infection. The progression of liver fibrosis results in hepatocellular carcinogenesis in later stages. Recent studies have revealed the importance of DNA hypermethylation in the progression of liver fibrosis to hepatocellular carcinoma (HCC). However, the importance of DNA methylation in the early-stage liver fibrosis remains unclear.
  
  
  METHODS
  To address this issue, we used a pathological mouse model of early-stage liver fibrosis that was induced by treatment with carbon tetrachloride (CCl4) for 2 weeks and performed a genome-wide analysis of DNA methylation status. This global analysis of DNA methylation was performed using a combination of methyl-binding protein (MBP)-based high throughput sequencing (MBP-seq) and bioinformatic tools, IPA and Oncomine. To confirm functional aspect of MBP-seq data, we complementary used biochemical methods, such as bisulfite modification and in-vitro-methylation assays.
  
  
  RESULTS
  The genome-wide analysis revealed that DNA methylation status was reduced throughout the genome because of CCl4 treatment in the early-stage liver fibrosis. Bioinformatic and biochemical analyses revealed that a gene associated with fibrosis, secreted phosphoprotein 1 (Spp1), which induces inflammation, was hypomethylated and its expression was up-regulated. These results suggest that DNA hypomethylation of the genes responsible for fibrosis may precede the onset of liver fibrosis. Moreover, Spp1 is also known to enhance tumor development. Using the web-based database, we revealed that Spp1 expression is increased in HCC.
  
  
  CONCLUSIONS
  Our study suggests that hypomethylation is crucial for the onset of and in the progression of liver fibrosis to HCC. The elucidation of this change in methylation status from the onset of fibrosis and subsequent progression to HCC may lead to a new clinical diagnosis.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba Science City, Ibaraki 305-8572, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Komatsu
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Waku
authors.forename: Naoya
authors.initials: N
authors.lastname: Iwasaki
authors.forename: Wakana
authors.initials: W
authors.lastname: Ono
authors.forename: Chie
authors.initials: C
authors.lastname: Yamaguchi
authors.forename: Junn
authors.initials: J
authors.lastname: Yanagisawa
mesh_terms: D000818:Animals; D002251:Carbon Tetrachloride / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D033481:Chromosomes, Mammalian / Q000235:genetics; D019295:Computational Biology; D019175:DNA Methylation / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D018450:Disease Progression; D044127:Epigenesis, Genetic / Q000235:genetics; D023281:Genomics; D059014:High-Throughput Nucleotide Sequencing; D008103:Liver Cirrhosis / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D058977:Molecular Sequence Annotation; D053495:Osteopontin / Q000235:genetics; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D004268:DNA-Binding Proteins; C506895:SPP1 protein, human; D053495:Osteopontin; D002251:Carbon Tetrachloride