Identification Of Key Genes Of Colorectal Cancer Expression Profiles By Integrated Analysis

Objectives:Colorectal cancer(CRC)is one of the most common malignant diseases in the world,but the involved driven-genes and signaling pathways are still unclear.This study integrated four expression profile datasets to clarify potential key genes and pathways in the development and progression of CRC.Methods:We selected four microarrays of GSE21815,GSE44076,GSE68468,and GSE74602,including 455 CRC and 144 normal mucosa.Differentially expressed genes(DGEs)were screened for gene ontology(GO)analysis and signaling pathway analysis.Protein-protein interaction(PPI)analysis was also carried out.After identifying the key genes,the relationship between the key genes and the prognosis of CRC was identified.Finally,6 CRC and para-cancerous tissues were used to verify the expression of key genes at the transcription and translation level through Quantitative Polymerase Chain Reaction(Q-PCR).Results:1.284 shared DEGs(143 up regulated and 141 down regulated)were identified from four GSE datasets;2.The DEGs were clustered based on function and signaling pathway with significant enrichment analysis.In the biological process(BP)group,the up-regulated genes are mainly enriched in the process of cell proliferation,cell motility and nuclear division,and the down-regulated genes are mainly enriched in the process of homeostasis and response to inorganic substance.In the molecular function(MF)group,the up-regulated genes are mainly enriched in endopeptidase activity,metal ion binding,protein binding etc.The down-regulated genes are mainly enriched in metal ion binding,substrate-specific channel activity,passive transmembrane transporter activity,etc.In the cellular component(CC)group,the up-regulated genes are mainly enriched in the extracellular matrix,chromosome,and microtubule cytoskeleton,and the down-regulated genes are mainly enriched in the perinuclear region of cytoplasm,extracellular region,extracellular exosome,extracellular vesicle and membrane-bounded vesicle.The signaling pathway enrichment analysis of up-regulation DEGs showed that the main enrichment pathways including progesterone-mediated oocyte maturation,p53 signaling pathway,cell cycle,focal adhesion and PI3K-Akt signaling pathway.The down-regulated genes are mainly enriched in mineral absorption,nitrogen metabolism,pancreatic secretion,steroid hormone biosynthesis,chemokines signaling pathway;3.The PPI network of DEGs included 291 nodes and 745 edges and identified 10 key candidate genes:TOP2A,CDK1,FOXM1,CCNB1,AURKA,BUB1,MAD2L1,TPX2,TTK,MYC.We found that these key candidate genes were mainly associated with cell cycle,meiosis and other signal pathways by DAVID analysis;4.We selected the 3 most significant modules from the PPI networks.The main signaling pathways involved in the 3 modules were cell cycle,oocyte meiosis,chemokine signaling pathway,TNF signaling pathway,cytokine-cytokine receptor interaction,neuroactive ligand-receptor interaction,and mineral absorption signaling pathway,etc.;5.We found that the key genes were related to the overall survival of CRC by using survival curves.6.The results of Q-PCR and Western Blot showed that the expression of 10 key candidate genes at transcriptional and translation level was consistent with the results of microarrays.Conclusions:1.Through the integrated bioinformatics analysis of multiple microarray expression profiling,we finally verified 284 differentially expressed genes.The common signaling pathways for differentially expressed genes are including cell cycle,chemokines,PI3K-Akt,P53 signaling pathways etc.;2.To screen out the 10 most significant key genes,these key genes involved in some important signal pathways such as cell cycle,meiosis and chemokines.The cell cycle-related pathway may be the focus of our later research.The key genes are associated with the prognosis of colorectal cancer and may be expected to become biological markers for the diagnosis and treatment of colorectal cancer;3.Through the experiments of Q-PCR and protein imprinting,the key genes expression of bioinformatics analysis has been verified,which not only shows the true reliability of the bioinformatics analysis results,but also validates the.relationship between these genes and the prognosis of colorectal cancer.Genes are expected to become molecular markers for the prognosis of colorectal cancer,and provide us with reliable experimental basis and theoretical basis for the subsequent study of the specific mechanisms of these key genes in the development of colorectal cancer.