| Background and Objective: The carcinogenesis of gastric carcinoma is related to many factors. Helicobacter pylori (Hp) infection is one of factors causing gastric carcinoma being verified, and its infection rate is very high in the world. Dalian is a gastric carcinoma prevalent city with high Hp infection rate, so there may be some relationship between them. The exact molecular mechanism of Hp infection causing carcinoma is not known though many study has been done. AMSH2 and /zMLHi are two types gene of mismatch repair system(MMR) which can repair the mutated genes and keep the stability of genome and the accuracy of DNA replication. The abnormal expression of MMR will lead gene mutation accumulate, manifested as over-expression of oncogene and deletion of tumor suppression gene. Some study reported that Hp infection could cause abnormal expression of tumor suppression gene, so we presumethere may be some abnormities in its upper-stream gene--the MMR. The reportsabout the relationship between Hp infection and MMR expression in gastric carcinoma are very rare. This study is designed to determine the relationship between Hp infection and MMR (hMSH2,hMLH1 ) expression in gastric carcinoma and discuss the possible mechanism of Hp infection causing carcinoma.Material and method: Gastric endoscopic biopsy specimens of 76 gastric carcinoma with their surrouding mucusa were got from the first affiliated hospital of Dalian medical university from 2002 to 2003. Guick -ureolytase method was used to detecte Hp infection. Immunohistochemical staining was used to examine the expression of hMSH2 and AMLH1 in tumor cells and their surrounding mucosa. Chi-square is used for statistic analysis.Results: Hp infection was detected in 44 cases, not detected in the other 32 cases. The infection rate was 57.9% (44/76).In carcinoma cells, the positive rate ofhMSH2 expression being 67.1% (51/76) was significantly higher than that of surrouding mucosa being 35.5% (27/76), (P<0.05): The positive rate of hMSH2 expression in low differentiated group being 87.1% (30/37) was significantly higher than that of high-middle differentiated group 54.5% (12/22), (P<0.05); The positive rate in mucous adenoma was 52.9% (9/17) and the common type was 71.1% (42/59) , it has no significant difference (P>0.05) .In carcinoma cells, the positive rate of hMLH1 expression was 81.6% (62/76) and the surrounding mucosa was 90.8% (69/76), it has no significant difference (P>0.05); The positive rate in low differentiated group was 97.2% (36/37) and 81.8% (18/22) in high-middle differentiated group, it has no significant difference (P>0.05) ; The positive rate in mucous adenocarcinoma being 47.1% (8/17) was significantly lower than that of common type being 88.1% (52/59), (P<0.05) .In carcinoma cells, the positive rate of hMSH2 expression of Hp(+)group being 56.8% (25/44) was significantly lower than that of Hp(-) group being 81.3% (26/32),(P<0.05); In surrouding mucosa, the positive rate of hMSH2 expression of Hp(+)group was 29.5% (13/44) and 43.7% (14/32) in Hp(-) group, it has no significant difference(P>0.05) ; In carcinoma cells, the positive rate of hMLH1 expression in Hp(+) group was 77.2% (34/44) and 87.5% (28/32) in Hp(-) group, it has no significant difference(P>0.05) ; In surrounding mucosa, the positive rate of hMLH1 expression in Hp(+) group was 86.4% (38/44) and 96.9% (31/32) in Hp(-)group, it has no significant difference (P>0.05) . Conclusions:1. The positive rate of hMSH2 expression in carcinoma cells was significantly higher than that of surrouding mucosa, and related to tumor differentiation.2. There is no significance between carcinoma and its surrouding mucosa in the positive rate of hMLH1 expression ; but the positive rate in mucous adenocaicinoma was significantly lower than that of commom type.3. Hp infection can not only suppress the expression of hMSH2 in carcinoma tissue,but also the normal mucosa .5. The abnormal expression of hMSH2 may be one mechanism of Hp causing carcinoma. Detection of...
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