Hypermethylation of the hMLH1 gene promoter in solitary and multiple gastric cancers with microsatellite instability.
Human cancers with a high frequency microsatellite instability phenotype develop due to defects in DNA mismatch repair genes. Silencing of a DNA mismatch repair gene, hMLH1 gene, by promoter hypermethylation is a frequent cause of the microsatellite instability-H phenotype. Using methylation specific PCR we investigated the methylation status of the hMLH1 gene promoter in 17 solitary gastric cancers (12 microsatellite instability-H and five microsatellite stable tumours from 17 patients), and 13 multiple gastric cancers (eight microsatellite instability-H, one low frequency microsatellite instability-L and four microsatellite stable tumours from five patients) and also examined non-cancerous gastric mucosa both adjacent to and distant from each tumour. Expression of hMLH1 protein was evaluated by immunohistochemistry. All microsatellite instability-H tumours (20 out of 20) had evidence of methylation of hMLH1 promoter, whereas only one out of 10 microsatellite instability-L and microsatellite stable tumours did (P<0.0000005), and the methylation status correlated with hMLH1 protein expression (P<0.000003). Furthermore, methylation of the hMLH1 promoter was detected in 50% (6 out of 12) and 63% (5 out of 8) of non-cancerous gastric mucosa samples adjacent to, and in 33% (4 out of 12) and 40% (2 out of 5) of those obtained from distant portion of, solitary and multiple cancers with microsatellite instability-H. Thus both solitary and multiple gastric cancers with microsatellite instability-H have evidence of similar high levels of hMLH1 promoter hypermethylation in the surrounding non-cancerous tissue. Hypermethylation of the hMLH1 promoter occurs in non-cancerous gastric mucosa of microsatellite instability-H tumours and may increase the risk of subsequent neoplasia.
Sakata
K
K
Department of Pathology, Yamagata University School of Medicine, Iida-nishi 2-2-2, Yamagata 990-9585, Japan.
Tamura
G
G
Endoh
Y
Y
Ohmura
K
K
Ogata
S
S
Motoyama
T
T
D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000145:classification / Q000235:genetics* / Q000473:pathology; D000368:Aged; D000369:Aged, 80 and over; D020137:Base Pair Mismatch / Q000235:genetics; D002352:Carrier Proteins; D019175:DNA Methylation; D004260:DNA Repair / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D020868:Gene Silencing; D006801:Humans; D007124:Immunoenzyme Techniques; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction / Q000379:methods; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000145:classification / Q000235:genetics* / Q000473:pathology; D014158:Transcription, Genetic
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1