Study On The MSI And HMSH2 Expression In Gastric Cancer And Precancerous Lesions

PURPOSE: To analyse the mechanism of gastric tumorigenesis induced by MSI and the gene mechanism leading to MSI in gastric carcinoma by studying the frequency of MSI and the hMSH2 expression in gastric carcinoma and precancerous lesions.MATERIALS AND METHODS: 57 biopsy specimens and 51 pathological specimens were collected randomly. The normal control samples of gastritis were mouth mucous membrane's cells falling during gargling and those of gastric carcinomas were the gastric mucous membrane, which were at least 5cm away from the cancer region. The specimens were divided into two groups and reserved in -80 癈. One group was used to extract DNA for MSI analysis; another group was used to detect hMSH2 by immunohistochemistry. The process of detecting the MSI is (1) using the phenol-chloroform-isopentanol method to extract the DNA; (2) PCR amplified; (3) denatured polyacrylamide gel electrophoresis; (4) silver stained for observing the result. The expression of hMSH2 gene was dectected by SABC immunohistochemistry.RESULTS:1. In gastritis, the frequency of MSI was 28.07% (12/57), and that of MSI-H was 5.26% (3/57). The frequency of MSI was 7.69%(1/14) in chronic superficial gastritis; 15%(3/20) in chronic atrophic gastritis; 33.33%(4/12) in chronic atrophic gastritis with intestinal metaplasia; 28.57%(2/7) in chronic atrophicgastritis with atypical hyperplasia; 50%(2/4) in chronic atrophic gastritis with intestinal metaplasia and atypical hyperplasia.2. In gastric carcinoma specimens, the frequency of MSI was 64.71%(33/51), and that of MSI-H was 17.65%(9/51). The positive rate of MSI in intestinal type gastric carcinomas was 79.17%( 19/24), while that of MSI-H was 33.33%(8/24). The positive rate of MSI in diffuse type gastric carcinomas was 50%( 11/22), while that of MSI-H was 4.55%(l/22). The frequency of MSI in intestinal type gastric carcinomas was significantly higher than that in diffuse type. And the frequency of MSI in papillary type adenocarcinoma was higher than that in the other pathology types. There wasn't significant difference of MSI frequency among age, gender in gastric carcinoma.3. In the specimens, there was only one hMSH2 expression absent sample(l/108) was detected. The pathological type was well-differentiated papillary adenocarcinoma.CONCLUSION: These results suggested that MSI maybe an early important incident in gastric tumorigenesis. The abnormal expression ol" mismatch repair gene hMSH2 maybe have no major responsibility for MSI.