Significance Of The Relationship Between Microsatellite Instability (MSI) And Clinicopathological Features In Gastric Cancer

Objective: We detected the expression pattern of MMR major proteins(MLH1,MSH2,MSH6 and PMS2)in 120 Chinese gastric cancers by using immunohistochemistry,and downloaded the results of microsatellite instability(MSI)in 432 cases with gastric cancer from the public database of The Cancer Genome Atlas(TCGA).This study aims to evaluate the significance of the relationship between microsatellite instability(MSI)and clinicopathological features in gastric cancer.Methods: Immunohistochemistry was used to detect the expression of MMR major proteins in 120 gastric cancer tissues,and the relationship between d MMR and clinicalpathological features had been explored.The clinical pathological data and microsatellite instability status of 432 patients with gastric cancer was downloaded from The Cancer Genome Atlas(TCGA,https://cancergenome.nih.gov/)public database.The relationship between d MMR/MSI-H and clinicopathological features was analyzed by chi-square test,sometimes using Fisher test.Survival analysis was performed by the Kaplan-Meier method.The Log-Rank test showed whether there was difference in the survival curve.P < 0.05 was considered statistically significant.Results: Of the 120 patients with gastric cancer,106 cases(88.3%)had normal expression of MMR,14 cases(11.7%)had deletion of MMR,including 2 cases(1.7%)MLH1 deletion,13 cases(10.8%)PMS2 deletion,2 cases(1.7%)combined MLH1 and PMS2 deletion,and 1 case(0.8%)combined MSH2 and MSH6 deletion.Statistical analysis showed that d MMR was only associated with lymph node metastasis of gastric cancer(P=0.022),but was not related to other clinicopathological factors.Statistical analysis about 432 cases of gastric cancer from TCGA database showed that MSI-H was significantly associated with age(P=0.001),gender(P=0.000),gastric cancer position(P=0.000),Lauren type(P=0.011),T stage(P=0.024),and lymph node metastasis(P=0.008).Kaplan-Meier analysis showed that the MSI-H gastric cancer had a better prognosis(P=0.070).Conclusion: In our study,we found that the proportion of MSI/d MMR in 120 gastric cancer patients was 11.7%,and d MMR was related to lymph node metastasis.Gastric cancer data from TCGA database suggested that MSI-H gastric cancer patients had the characteristics of distal location of the stomach,lower T stage and Non-lymph node metastasis.Survival analysis of TCGA gastric cancer data showed that MSI-H gastric cancer had a better prognosis.The relationships between MSI status and gastric cancer prognosis and chemotherapy need further research and validation from large sample data in future.