摘要
AIM: To investigate CpG methylation and single nucleotidepolymorphism (SNP) of a specific promoter region of hMLH11in primary gastric carcinoma.METHODS: Primary gastric carcinomas (7＝80), theircorresponding normal mucosal samples, and gastric mucosalbiopsies from normal/gastritis control patients (n＝54) wereused. Hypermethylation at -253 nt and -251 nt in relationwith the translational start site and SNP of a silencing specificregion (-339 nt-46 nt) in the hMLH-1 promoter were analyzedby BstUI-combined bisulfite assay (COBRA), denaturing highperformance liquid chromatogram (DHPLC), and sequencing.RESULTS: (A) The specific methylation at -253 nt and -251nt was observed in 2 of 60 primary gastric carcinomas, butneither in all of the corresponding mucosa nor in normal/gastritis samples, by Bst UI-COBRA and DHPLC. (B) ThehMLH1 promoter was methylated homogeneously in thexenograft of the primary gastric carcinoma with themethylated and unmethylated hMLH11. (C) The pattern ofSNP at -93 nt of the hMLH11 promoter in 54 Chinese patientswith gastric carcinoma was the same as that in the controlpatients: 51% was A/G heteroalleles, 34 % and 15 % wereA/A and G/G homoalleles, respectively.CONCLUSION: Biallelic inactivation of hMLH1 by epigeneticsilencing existed in human primary gastric carcinomahomogeneously. Hypermethylation of hMLH11 may play arole in the early stage of development of a few gastriccarcinomas. The SNP at -93 nt is not related to thesusceptibility of gastric carcinomas.
AIM:To investigate CpG methylation and single nucleotide polymorphism(SNP)of a specific promoter region of hMLH1 in primary gastric carcinoma. METHODS:Primary gastric carcinomas(n=80),their corresponding normal mucosal samples,and gastric mucosal biopsies from normal/gastritis control patients(n=54)were used.Hypermethylation at-253 nt and-251 nt in relation with the translational start site and SNP of a silencing specific region(-339 nt-46 nt)in the hMLH1 promoter were analyzed by BstUI-combined bisulfite assay(COBRA),denaturing high performance liquid chromatogram(DHPLC),and sequencing. RESULTS:(A)The specific methylation at-253 nt and-251 nt was observed in 2 of 60 primary gastric carcinomas,but neither in all of the corresponding mucosa nor in normal/ gastritis samples,by Bst UI-COBRA and DHPLC.(B)The hMLH1 promoter was methylated homogeneously in the xenograft of the primary gastric carcinoma with the methylated and unmethylated hMLH1.(C)The pattern of SNP at-93 nt of the hMLH1 promoter in 54 Chinese patients with gastric carcinoma was the same as that in the control patients:51% was A/G heteroalleles,34% and 15% were A/A and G/G homoalleles,respectively. CONCLUSION:Biallelic inactivation of hMLH1 by epigenetic silencing existed in human primary gastric carcinoma homogeneously.Hypermethylation of hMLH1 may play a role in the early stage of development of a few gastric carcinomas.The SNP at-93 nt is not related to the susceptibility of gastric carcinomas.
基金
grant(2000-A-29)from Peking University Center for Human Disease Genomics
grant(0106)from Peking University Cancer Research Center
grant(3171045)from National Natural Science Foundation of China,and by NIH Grant CA67900
