The Study Of Correlation Between Microsatellite Instability And Esophageal Cancerization

Objective: As mutations of the human mismatch repair (MMR) gene can lead to the activation of oncogenes or inactivation of cancer suppressor gene which intiate the process of cell cancerization. In this paper, we analyzed the microsatellite instability in sporadic squamous cell carcinoma (SCC) and Barrett's adenocarcinoma (BA) to investigate the percentage of MSI and the relation of tumorgenesis. In MSI positive samples, we analyzed the RIZ gene in order to find the target gene in the esophageal cancerization. It can provide more effective basis for earlier diagnosis and therapy of esophageal cancer.Methods: All resected samples for the experiment was obtained from the patients with sporadic esophageal cancer of the department of chest surgery in Hebei Medical University No. 4 Hospital. Resected tumor and its edge as well as normal tissue(apart from tumor tissue at least 5centimetre) were collected and stored at -80℃ refrigeratory quickly. Tumor and normal tissue DNA were obtained from eighty patients with sporadic esophageal cancer using standard extraction techniques. Microsatellite sequences at BAT-26 was amplified by polymerase chain reaction (PCR)reaction. Amplified products were analyzed by 7% acrylamide gels electrophoresis for microsatellite analysis. Microsatellite instability was scored as present when an abnormal band occurred in the tumor sample when compared to the corresponding normal DNA sample. In addition, we studied RIZ mutations in sporadic esophageal cancer with microsatellite instability. We studied the mutation in the two coding polyadenosine tracks of RIZ by PCR-SSCP silver stain in order to identify the correlation of the suppressor gene and the esophageal cancerization. Results: 1.Genetic DNA was obtained from eighty patients of sporadic esophageal cancer and was amplified with microsatellite marker BAT-26. Amplified products were analyzed by 7% denaturing acrylamide gels electrophoresis. Fifteen of eighty cancers were detected as unstable. Microsatellite instability (MSI) is observed in 18.75% of esophageal cancer. 2. The relationship between MSI and histological type: MSI was identified in seven of fifty-two sporadic squamous cell carcinoma (SCC) patients (15.4%), while MSI was observed in two of twenty-three sporadic Barrett's adenocarcinoma (BA) patients(8.7%). Five small-cell carcinoma patients were all found MSI (100%). The results analyzed by using SAS software showed that the relationship between MSI and histological type is statistically significant (p<0.05, χ2 test), that is to say, the incidence of small-cell carcinoma is significantly higher than patients ofsquamous cell carcinoma (SCC) and Barrett's adenocarcinoma (BA). 3. The relationship between MSI and patients' sex, age and tumor metastasis: MSI was observed in ten of fifty-one male esophageal cancer patients (19.6%), while MSI was identified in five of twenty-nine female patients (17.2%). The presence of MSI did not correlate with patient sex by using SAS software (p>0.05, χ2 test). MSI was found in four of twenty-eight patients less than fifty-five years old (14.2%), while MSI was observed in eleven of fifty-two patients more than fifty-five years old (21.1%). With the analysis of SAS, there is no association with the patient age (p>0.05). MSI was identified in eight of forty-three patients with no lymph node metastasis (18.6), while MSI was observed in seven of thirty-seven patients with lymph node metastasis (18.9%). The incidence of MSI did not correlate with the tumor progress (p>0.05); 4. We studied the RIZ mutation in fifteen MSI patients. Mutations in the two coding polyadenosine tracks of RIZ were found in six of fifteen MSI patients by SSCP silver stain(40%) with abnormal bands. Therefore, mutations of RIZ were a close association with the presence of MSI. The result suggested that RIZ gene was possible a target gene of esophageal cancerization with impairment of the PR domain-mediated function through either frameshift mutation or genomic deletion.Conclusions: 1. We detected...