Satoshi Yoshida1,2, Satoshi Yamashita1, Tohru Niwa1, Akiko Mori1, Seiji Ito3, Masao Ichinose2, Toshikazu Ushijima4. 1. Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan. 2. Second Department of Internal Medicine, Wakayama Medical University, Wakayama, Japan. 3. Department of Gastroenterological Surgery, Aichi Cancer Center Central Hospital, Nagoya, Japan. 4. Division of Epigenomics, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo, 104-0045, Japan. tushijim@ncc.go.jp.
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.
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.
Entities:
Keywords:
CpG island methylator phenotype; DNA methylation; FAT4; Gastric cancer; Helicobacter pylori
Authors: E Okochi-Takada; N Hattori; T Tsukamoto; K Miyamoto; T Ando; S Ito; Y Yamamura; M Wakabayashi; Y Nobeyama; T Ushijima Journal: Oncogene Date: 2013-05-20 Impact factor: 9.867