The Study Of Molecular Mechanisms Involved In The Pathogenesis Of Gastric Carcinoma And Precancerous Lesion

Aims:To explore the molecular marker for early diagnosis of gastric carcinoma and further study the molecular mechanisms involved in the pathogenesis of gastric carcinoma and pre-cancerous lesions.Methods:1. A tissue microarray derived from gastric carcinoma and precancerous lesions was constructed. Immunohistochemistry was used to detected the expression of oncogenes, suppressor genes, apoptosis associated genes, cell cycle proteins, adherin molecules and mismatch repair gene in all the samples of tissue microarry.2. The microsatellite instability (MSI) was detected in gastric carcinoma and precancerous lesions by tissue laser capture microdissection, polymerase chain reaction and denaturing high performance liquid chromatogragh (DHPLC).3 . The mitochondrial mutation and MSI from tumor and paired normal DNA was examined after laser capture microdissection.Results:1. A tissue microarray including 48 cases of gastric carcinoma, 33 cases of gastric hyperplasia, 19 cases of intestinal metaplasia and 17 cases of normal gastric mucosa tissues was constructed. Histological appearance was well preserved in most dots of the micorarry section.2. The expression patterns of most carcinoma-related genes were well related with the biological behavior of normal tissues, precancerous tissue and gastric cancerous tissues. Some of them showed certain tendency from normal to cancerous tissues (P<0. 05) .3. MSI were found in 10.5% intestinal metaplasia, 21.12% gastric hyperplasia and 43.75% gastric carcinoma respectively which displayed accumulation and alteration from normal to cancerous tissues.4. The mitochondrial genetic mutation was detected in D-loop region, ND1 and ND5 genes which belong to electron respiratory chain complex I. The mutation frequencies among them were 50.8%, 39.3% and 21.3% respectively while the control group of paired normal tissues found no mitochondrial genetic mutation. The mitochondrial microsatellite instability (mtMSI) was detected in 18/61(29.5%) gastric carcinomas at D-loop (CA)n region and there existed 8/18(44.4%) nuclear microsatellite instability(nMSI-H) simultaneous.Conclusions:1. Tissue microarray technology has the advantages of highthroughput,economic and accurate screening of clinical tissue specimens on a large scale.2. The multiple genetic alteration and accumulation may play an important role in the oncogenesis and progression of gastric carcinoma. It can provide evidence for understanding the occurrence and progression of gastric carcinoma.3. Pure samples were obtained after tissue laser capture microdissection. It successfully resolved the heteroplasmy of tissue.4. DHPLC is a high sensitive, fast and semiautomated method for identifying MSI and mutation.5. Our experiments showed an increasing tendency of MSI incidence from precancerous lesion to gastric carcinoma, it provided the evidence that MSI may be involved in the whole process of gastric carcinoma occurrence. MSI is an early issue in gastric carcinoma and could be used as a marker to predicate the occurrence of gastric carcinoma.6. A considerable proportion of mitochondrial DNA mutation was found in gastric carcinoma, it suggested that mitochondrial DNA mutation may be one of important reasons for tumorgenesis of gastric carcinoma. Further study showed that many gastric carcinomas coexisted the mitochondrial and nuclear DNA instability which indicated that they together take part in the progression of gastric carcinoma.