Analysis Of Mismatch Repair Defect/Microsatellite Instability-related Colorectal Cancer Gene Mutations Based On High-throughput Sequencing

Objective:In recent years,there are many new advances in diagnosis and molecular pathogenesis of mismatch repair defects and microsatellite instability colorectal cancer.But the systematic analysis of gene expression profiles of different disease stages,the effect of mutated genes on disease progression and prognosis of PD-1/PD-L1 treatment are still lacking.The purpose of this thesis is as follows: 1.Describing the gene expression differences in patients with different pathological stages;2.Exploring the molecular mechanism of disease progression in patients with Lynch syndrome colorectal cancer;3.Discussing the molecular basis of mutation gene differences on the prognosis of PD-1/PD-L1 treatment.Method:Using Next-Generation Sequencing(high-throughput sequencing)as the main research method,this study performed sequencing analysis on patients with gastrointestinal tumors with early stage and advanced stage mismatch gene deletion or high microsatellite instability.Based on the comparison of gene mutation differences,signal transduction differences and diversion or enrichment of metabolic pathways between different patient groups,we will obtain the gene profiles or signal pathways expressions with significantly different.According to the catalytic mechanisms or structural changes caused by specific mutation sites,the molecular mechanisms of tumorigenesis and disease progression are analyzed.Results:1.A total of 47 patients diagnosed with dMMR/MSI-H colorectal cancer were included for genetic analysis.The age ranges from 26 to 80 years,with an average age of 48.6 years and a median age of 48 years.2.Microsatellite instability relatedMLH1,MSH2,MSH6,and PMS2 genes have somatic mutations,and there is no significant difference in the frequency of mutations in patients with early and advanced stages,while germline mutations are apparent in patients with early and advanced stages.3.Among the 378 mutant target genes,63 genes are unique to the early stage clinical case.There are 35 genes that are unique to advanced stage clinical cases through KEGG enrichment analysis.Mutated genes mainly affect the following related metabolic pathways and signaling pathways.4.Chi-square test was used to analyze the difference between somatic gene mutations related to early stage and advanced stage colorectal cancer,and it was determined that the frequency of five key mutation genes in early stage patients was significantly higher than that in advanced stage patients(P <0.05).At the same time,it was determined that the frequency of five key mutation genes in advanced stage patients was significantly higher than that in patients in early stage(P <0.05).Conclusion:1.After a systematic comparison of the mutation genes in the early stage patients and the advanced stage patients,it was found that among the mutational hotspots of advanced stage patients,the effector proteins TSC2,SMAD3,FGFR1,and PTPN13 all participate in the cell’s main signaling pathways.Mutations in related genes are more likely to cause cell division,proliferation,and migration disorders,causing disease progression.It may be one of the reasons for poor prognosis of advanced dMMR/MSI-H colorectal cancer.2.In patients with advanced stage,specific genes related to the PI3K-Akt signaling pathway and are Ras-Raf-MEK-ERK signaling pathway abnormal.The inhibitory effect of these signaling pathways can affect PD-1/PD-L1 expression.This study preliminarily explored the effective mechanism of immunotherapy in patients with dmmr / MSI-H colorectal cancer.