AIM:To explore the effect of DNA methyltransferase,clemethylase and methyI-CpG binding protein MeCP2 onthe expressions and methylation of hMSH2 and proto-oncogene in human gastric cancer.METHODS:Paired samples of primary gastric cancer andcorresponding para-cancerous,non-cancerous gastric mucosaewere obtained from surgically resected specimens of 28patients.Transcription levels of Dnmtl,mbd2,MeCP2,p16~(INK4A),hMSH2 and c-myc were detected by using real-time PCRor RT-PCR.Promoter methylation of p16~(NK4A),C-myC andhMSH2 genes was assayed by methylation-specific PCR(MSP)and sequencing(mapping).Their relationships wereanalyzed by Fisher’s exact test using the software SPSS.RESULTS:The average mRNA level of Dnmtl gene fromcancerous tissue was higher and that of mbd2 gene fromcancerous tissue was lower than that from non-canceroustissue,respectively,mbd2 was lower in cancerous tissuethan in non-cancerous tissue in 14(50.0%)of patients buthigher in 3 cases(10.7%)of non-cancerous gastric tissue(P<0.001).c-myc expression was up-regulated in cancertissues(P<0.05).The up-regulation of mbd2 was found inall patients with hypomethylated c-myc.The transcriptionallevels of p16~(INK4A)and MeCP2 genes did not display any differencebetween gastric cancerous and matched non-canceroustissues.There were down-regulation and hypermethylationof hMSH2 in cancer tissues,and the hypermethylation ofhMSH2 coexisted with down-regulated transcription.However,the transcription level of the above genes wasnot associated with biological behaviours of gastric cancers.CONCLUSION:The up-regulation of proto-oncogene maybe the consequence of epigenetic control of gene expressionby demethylase,and mbd2 is involved in the regulation ofhMSH2 expression in human gastric cancer. AIM: To explore the effect of DNA methyltransferase, clemethylase and methyI-CpG binding protein MeCP2 on the expressions and methylation of hMSH2 and proto-oncogene in human gastric cancer. METHODS: Paired samples of primary gastric cancer andcorresponding para-cancerous, non-cancerous gastric mucosaewere obtained from surgically resected specimens of 28patients. Transcription levels of Dnmtl, mbd2, MeCP2, p16 ~ (INK4A), hMSH2 and c-myc were detected by using real-time PCRor RT- The rumors were analyzed by Fisher’s exact test using the software SPSS. RESULTS: The average mRNA level of Dnmtl gene from cancer tissue was higher and that of mbd2 gene from cancerous tissue was lower than that from non-cancerous tissue, respectively, mbd2 was lower in cancerous tissuethan in non-cancerous tissue in 14 (50.0%) of patients buthigher in 3 cases (10.7%) of non-cancerous tissue The up-regulation of mbd2 was found in patients with hypomethylated c-myc. The transcriptionallevels of p16 ~ (INK4A) and MeCP2 genes (p <0.001) .c-myc expression was up-regulated in cancertissues did not display any difference between gastric cancerous and matched non-cancerous tissues. Where were down-regulation and hypermethylation of hMSH2 in cancer tissues, and the hypermethylation of hMSH2 coexisted with down-regulated transcription. Host, the transcription level of the above genes wasnot associated with biological behaviors of gastric cancers. CONCLUSION: The up-regulation of proto-oncogene maybe the consequence of epigenetic control of gene expression by demethylase, and mbd2 is involved in the regulation of hMSH2 expression in human gastric cancer.