Prediction And Preliminary Verification Of Prognostic-related Genes In Gastric Adenocarcinoma

ObjectiveThis study aims to screen the differentially expressed genes of primary gastric adenocarcinoma by bioinformatics method,analyze the biological function of the selected genes,explore the correlation between their expression level and clinic pathological characteristics in patients with primary gastric adenocarcinoma,and provide a new idea for prognosis evaluation.Method1.Three RNA sequencing datasets were downloaded from GEO and TCGA databases,and the limma and edge R packages were used for differential expression analysis of these datastes to screen out the differentially expressed genes.Then the differentially expressed genes were analyzed by GO enrichment analysis and KEGG pathway analysis using David software,and String and Cytoscape were used for protein interaction network analysis of the differentially expressed genes.K-M was performed by survival analysis.2.A total of 148 patients with primary gastric adenocarcinoma who underwent radical gastrectomy in Sichuan Provincial People’s Hospital from October 2016 to February 2018 were collected.Immunohistochemistry(manual HRP-polymer method)was used to detect the expression levels of COL1A1 and COL1A2 in the tissues and adjacent tissues of primary gastric adenocarcinoma.At the same time,statistical methods were conducted to analyze the correlation between clinicopathological characteristics and the expression levels of COL1A1 and COL1A2,and evaluate the prognosis of patients.Results1.By integrating three datasets of GSE103236,GSE26899 and TCGA-STAD,63 DEGs were obtained,of which 30 were up-regulated and 33 were down-regulated.GO enrichment analysis showed that differentially expressed genes were mainly involved in the formation of extracellular tissues,extracellular matrix tissues,collagen fibrous tissues,collagen trimer complex and collagen-containing extracellular matrix,and had oxidoreductase activity(including CH-OH group containing donor,NAD or NADP as receptors).KEGG pathway analysis showed that the main enrichment pathways of DEGS were protein digestion and absorption,chemical carcinogenesis,drug metabolism-cytochrome P450,gastric acid secretion,and metabolism of cytochrome P450 to allogeneic organisms.Twenty core genes including COL1A1,COL1A2,THBS2,SPP1 and TIMP1 were screened out by String and Cytoscape.K-M analysis indicated that the expressions of 17 core genes including COL1A1 and COL1A2 were related to the prognosis of the patients.2.Immunohistochemical analysis showed that the expression levels of COL1A1 and COL1A2 in adjacent tissues were significantly lower than those in cancer tissues(both P=0.000).Univariate analysis results showed that the maximum diameter of the tumor(P= 0.039),the pathological type of the tumor(P=0.019),TNM stage(P=0.031),COL1A1 expression level(P=0.035),COL1A2 expression level(P=0.045),Ki67-positive index(P=0.041)and P53(P=0.039)were correlated with median progression-free survival after surgery.Multivariate Cox regression showed that the independent risk factors for postoperative survival of patients with primary gastric adenocarcinoma included TNM stage(primary P=0.001),COL1A1 expression level(P=0.038)and COL1A2 expression level(P=0.048).ConclusionThis study suggests that the overexpression of COL1A1 and COL1A2 is closely related to poor prognosis,COL1A1 and COL1A2 may be a reference index for prognosis evaluation of primary gastric adenocarcinoma...