title: Helicobacter pylori impairs DNA mismatch repair in gastric epithelial cells.
abstract: OBJECTIVE
  Helicobacter pylori infection is a major gastric cancer risk factor. H. pylori gastritis occurs more frequently in individuals with microsatellite instability-positive than those with microsatellite instability-negative gastric cancers, raising the possibility that H. pylori infection affects DNA mismatch repair (MMR). The aim of this study was to determine the effect of H. pylori on the expression of DNA MMR proteins and RNA in gastric epithelial cells.
  
  
  METHODS
  Gastric cancer cell lines were cocultured with H. pylori, bacterial extracts, and Campylobacter jejuni or Escherichia coli. MutS (hMSH2 and hMSH6) and MutL (hMLH1, hPMS2, and hPMS1) DNA MMR protein and RNA levels were determined.
  
  
  RESULTS
  All cell lines examined showed decreased levels of MutS and MutL DNA MMR proteins in a dose-dependent manner after coculture with H. pylori strains. The reduction in DNA MMR protein levels was caused by heat-sensitive H. pylori products. The levels of DNA MMR proteins were affected by C. jejuni but not by E. coli. RNA levels of hMSH2 and hMSH6 were also reduced after exposure to H. pylori.
  
  
  CONCLUSIONS
  H. pylori infection of gastric epithelial cells leads to a decrease in DNA MMR proteins that is at least in part related to an H. pylori-induced decrease in messenger RNA levels of repair genes. These data suggest that H. pylori infection might lead to a deficiency of DNA MMR in gastric epithelial cells that may increase the risk of mutation accumulation in gastric mucosa cells and the risk of gastric cancer during chronic H. pylori infection.
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jae J
authors.initials: JJ
authors.lastname: Kim
authors.forename: Hong
authors.initials: H
authors.lastname: Tao
authors.forename: Emilia
authors.initials: E
authors.lastname: Carloni
authors.forename: Wai K
authors.initials: WK
authors.lastname: Leung
authors.forename: David Y
authors.initials: DY
authors.lastname: Graham
authors.forename: Antonia R
authors.initials: AR
authors.lastname: Sepulveda
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000032:analysis; D005753:Gastric Mucosa / Q000378:metabolism*; D016480:Helicobacter pylori / Q000472:pathogenicity*; D006801:Humans; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000032:analysis; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D011518:Proto-Oncogene Proteins / Q000032:analysis; D013274:Stomach Neoplasms / Q000209:etiology; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein