Identification Of Differentially Expressed Genes In Rectal Cancer By Integrated Bioinformatics Analysis

Background and objective: Colorectal cancer is the third most common malignant tumor in the world.In China,the incidence of rectal cancer accounts for about 60% of colorectal cancer,and its clinical prognosis is poor.This study identified differentially expressed genes in rectal cancer by bioinformatics analysis to provide new therapeutic targets for rectal cancer.Materials and methods: The data sets of GSE20842,GSE136735 and GSE139814 gene chips were downloaded from GEO database,and the differentially expressed genes in rectal cancer were obtained by GEO2 R.The GO(Gene Ontology)analysis and KEGG(Kyoto Encyclopediaof Geneand Genomes)pathway analysis of the selected differentially expressed genes were performed by R-packet cluster Profiler and used to explain the enrichment of differentially expressed genes.The protein-protein interaction network was constructed by STRING database.The core network genes in protein-protein interaction network were screened by Cytoscape software,and their differentially expressed genes were verified in TCGA database.Results: A total of 379 differentially expressed genes were found in this experiment,with the same expression trend of 376 genes,including 179 up-regulated genes and 197 down-regulated genes(adjusted p <0.05 and | log2 FC |> 2).Through GO enrichment analysis(p <0.05),they found that they were mainly involved in biological processes such as collagen catabolism,inflammatory response,chemotaxis of neutrophils,bicarbonate transport,and one-carbon metabolism.The molecular functions mainly include chemokine receptor binding,serine-type endopeptidase activity,chemokine activity and other functions;after analysis of cell composition,these differential genes are mainly concentrated in the extracellular matrix.KEGG pathway enrichment analysis(p <0.05)showed that the main signalling pathways include signalling processes such as cytokine-cytokine receptor interactions,protein digestion and absorption,and nitrogen metabolism.Cytohubba(Software in Cytoscape)analysis revealed TIMP metallopeptidase inhibitor 1(TIMP1),keratin 20(KRT20),recombinant human secretin-2(SCG2),matrix metalloproteinase-3(MMP3),CXC motif chemokine ligand 2(CX-Cmotifchemokineligand2,CXCL2),snail family transcription repressor 1(SNAI1),matrix metalloproteinase-7(matrixmetallopeptidase7,MMP7),chromogranin A,CHGA),Peptide YY(peptide YY,PYY),thrombospondin 2(THBS2),chromogranin B(CHGB),somatostatin(SST),glucagon(GCG),Aggrecan(ACAN),serum amyloid A1(serumamyloid A1,SAA1).These 15 genes may be key genes for inducing the development of rectal cancer(p <0.05).These 15 genes were further verified by the TCGA database,and the key genes of MMP3,CXCL2,ACAN,and TIMP1 were further screened,and these 4 genes were highly expressed in rectal cancer(p <0.05).Conclusion: This study shows that the differentially expressed genes of rectal cancer and normal intestinal tissue can be effectively analyzed by bioinformatics analysis.A total of 4 differentially expressed genes were screened out in this study,namely MMP3,CXCL2,ACAN,and TIMP1,indicating that they may be new biomarkers for the pathogenesis of rectal cancer.