Biomarker-based Study Of Immune-Associated Biomarker For Colorectal Cancer

PART1 IDENTIFICATION OF A TWO-GENE PROGNOSTIC MODEL ASSOCIATED WITH CYTOLYTIC ACTIVITY FOR COLON CANCERBackground: Increasing evidence has shown that cytolytic activity(CYT)is a new immunotherapy biomarker that characterises the antitumour immune activity of cytotoxic T cells and macrophages.In this study,we established a prognostic model associated with CYT.Methods: A prognostic model based on CYT-related genes was developed.Furthermore,aberrant expression of genes of the model in colon cancer(CC)was identified by reverse transcription-quantitative polymerase chain reaction(RT-q PCR)and immunohistochemistry(IHC)assays.Next,the correlation between the model and T-cell infiltration in the CC microenvironment was analysed.The Tumour Immune Dysfunction and Exclusion(TIDE)algorithm and subclass mapping were used to predict clinical responses to immune checkpoint inhibitors.Results: In total,280 of the 1418 genes were differentially expressed based on CYT.A prognostic model(including HOXC8 and MS4A2)was developed based on CYT-related genes.The model was validated using the testing set,the whole set and a Gene Expression Omnibus(GEO)cohort(GSE41258).Gene set enrichment analysis(GSEA)and other analyses showed that the levels of immune infiltration and antitumour immune activation in low-risk-score tumours were greater than those in high-risk-score tumours.CC patients with a low-risk-score showed more promise in the response to anti-immune checkpoint therapy.Conclusions: Overall,our model may precisely predict the overall survival of CC and reflect the strength of antitumour immune activity in the CC microenvironment.Furthermore,the model may be a predictive factor for the response to immunotherapy.PART2 MULTI-DATABASE ANALYSIS OF THE EXPRESSION AND CLINICAL SIGNIFICANCE OF ARHGAP44 IN COLORECTAL CANCERObjective: To investigate the expression of Rho GTPase activating protein 44(ARHGAP44)in colorectal tissue and its relationship with the clinicopathological characteristics and prognosis of colorectal cancer in multiple data sets.Methods: With the use of the gene expression omnibus(GEO)and the cancer genome atlas(TCGA)cohorts,we summarized the expression of ARHGAP44 and its relationship with clinicopathological characteristics of colorectal cancer,evaluated the prognostic value by the Cox regression model and Kaplan-Meier curve.The m RNA expression of ARHGAP44 was validated in clinical samples by RT-q PCR.And gene set enrichment analysis(GSEA)was used to predict the pathway.Using the ss GSEA(single-sample gene-set enrichment analysis)algorithm,the association between ARHGAP44 and immune cell infiltration was calculated.Results: In TCGA,GEO datasets and clinical samples,the ARHGAP44 expressions were reduced in tumor tissues(P<0.001),and related to T stage,N stage,TNM stage(P<0.05).The low expression of ARHGAP44 showed an independent risk factor for OS(overall survival)of colorectal cancer patients(HR=0.44,P=0.02).GSEA results showed that the high expression samples of ARHGAP44 were rich in colorectal cancer pathway,Notch pathway,T cell receptor pathway,B cell receptor pathway and other gene sets.The expression of ARHGAP44 was negatively correlated with the infiltration levels of macrophages,T helper cells,TIL(tumor-infiltrating lymphocytes)and type ? IFN response(cor=-0.35,-0.37,-0.33,-0.35,-0.23 and-0.32,P=0.008,0.006,0.027,0.021,0.041 and 0.021).Conclusion: The expression of ARHGAP44 is down-regulated in colorectal cancer,which can be used as an independent prognostic biomarker for survival,and has a potential role in tumor immunology.