title: Mutation and methylation of hMLH1 in gastric carcinomas with microsatellite instability.
abstract: OBJECTIVE
  To appraise the correlation of mutation and methylation of hMSH1 with microsatellite instability (MSI) in gastric cancers.
  
  
  METHODS
  Mutation of hMLH1 was detected by Two-dimensional electrophoresis (Two-D) and DNA sequencing; Methylation of hMLH1 promoter was measured with methylation-specific PCR; MSI was analyzed by PCR-based methods.
  
  
  RESULTS
  Sixty-eight cases of sporadic gastric carcinoma were studied for mutation and methylation of hMLH1 promoter and MSI. Three mutations were found, two of them were caused by a single bp substitution and one was caused by a 2 bp substitution, which displayed similar Two-D band pattern. Methylation of hMLH1 promoter was detected in 11(16.2 %) gastric cancer. By using five MSI markers, MSI in at least one locus was detected in 17/68(25 %) of the tumors analyzed. Three hMLH1 mutations were all detected in MSI-H (>=2 loci, n=8), but no mutation was found in MSI-L (only one locus, n=9) or MSS (tumor lacking MSI or stable, n=51). Methylation frequency of hMLH1 in MSI-H (87.5 %, 7/8) was significantly higher than that in MSI-L (11.1 %, 1/9) or MSS (5.9 %, 3/51) (P<0.01-0.001), but no difference was found between MSI-L and MSS (P>0.05).
  
  
  CONCLUSIONS
  Both mutation and methylation of hMLH1 are involved in the MSI pathway but not related to the LOH pathway in gastric carcinogenesis.
authors.affiliation: Southwest Hospital, Third Military Medical University, Chongqing 400038, China. fangdianchun@hotmail.com
authors.forename: Dian-Chun
authors.initials: DC
authors.lastname: Fang
authors.forename: Rong-Quan
authors.initials: RQ
authors.lastname: Wang
authors.forename: Shi-Ming
authors.initials: SM
authors.lastname: Yang
authors.forename: Jian-Ming
authors.initials: JM
authors.lastname: Yang
authors.forename: Hai-Feng
authors.initials: HF
authors.lastname: Liu
authors.forename: Gui-Yong
authors.initials: GY
authors.lastname: Peng
authors.forename: Tian-Li
authors.initials: TL
authors.lastname: Xiao
authors.forename: Yuan-Hui
authors.initials: YH
authors.lastname: Luo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch / Q000235:genetics; D001483:Base Sequence; D002352:Carrier Proteins; D019175:DNA Methylation; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics* / Q000302:isolation & purification; D005091:Exons; D006801:Humans; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1