title: Epigenetic inactivation of FAT4 contributes to gastric field cancerization.
abstract: BACKGROUND
  Gastric cancer (GC) is highly influenced by aberrant methylation, and accumulation of aberrant methylation in gastric mucosae produces an epigenetic field for cancerization. Nevertheless, the individual driver genes involved in such field cancerization are still unclear. Here, we aimed to demonstrate that FAT4, a novel tumor suppressor identified by exome sequencing of GC, is methylation-silenced and that such methylation is involved in epigenetic field cancerization for GC.
  
  
  METHODS
  A transcription start site was determined by the 5' rapid amplification of complementary DNA ends method. DNA methylation was analyzed by bisulfite sequencing with use of a next-generation sequencer or quantitative methylation-specific PCR. Gene expression was analyzed by quantitative reverse transcription PCR.
  
  
  RESULTS
  A single transcription start site was identified for FAT4 in gastric epithelial cells, and a CpG island was located in the FAT4 promoter region. FAT4 was highly methylated in two of 13 GC cell lines and was not expressed in them. Removal of FAT4 methylation by a DNA demethylating agent (5-aza-2'-deoxycytidine) restored its expression in the two cell lines. In primary GC samples, FAT4 was methylated in 12 of 82 GCs (14.6 %). FAT4 methylation was associated with the presence of the CpG island methylator phenotype but not with prognosis, tumor invasion, lymph node metastasis, or histological types. In noncancerous gastric mucosae, high FAT4 methylation levels were associated with the presence of GC and Helicobacter pylori infection.
  
  
  CONCLUSIONS
  FAT4 was methylation-silenced in GCs. Its methylation in gastric mucosae was associated with H. pylori infection and likely contributed to epigenetic field cancerization.
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan.|Second Department of Internal Medicine, Wakayama Medical University, Wakayama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Niwa
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Mori
authors.affiliation: Department of Gastroenterological Surgery, Aichi Cancer Center Central Hospital, Nagoya, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Ito
authors.affiliation: Second Department of Internal Medicine, Wakayama Medical University, Wakayama, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Ichinose
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan. tushijim@ncc.go.jp.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Ushijima
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics*; D015820:Cadherins / Q000235:genetics*; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic / Q000235:genetics*; D005753:Gastric Mucosa / Q000378:metabolism / Q000821:virology; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery / Q000821:virology; D046152:Gastrointestinal Stromal Tumors / Q000235:genetics* / Q000473:pathology / Q000601:surgery / Q000821:virology; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016481:Helicobacter Infections / Q000821:virology; D016480:Helicobacter pylori / Q000302:isolation & purification; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D009367:Neoplasm Staging; D010641:Phenotype; D011379:Prognosis; D011401:Promoter Regions, Genetic; D060888:Real-Time Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery / Q000821:virology; D015996:Survival Rate; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; D015820:Cadherins; C534294:FAT4 protein, human; D025521:Tumor Suppressor Proteins
keywords: CpG island methylator phenotype; DNA methylation; FAT4; Gastric cancer; Helicobacter pylori