Profiles of immune cell infiltration and immune-related genes in the tumor microenvironment of colorectal cancer

Purpose: tumor-infiltrating immune cells are highly relevant to the progression and prognosis of colorectal cancer (CRC). The aim of this study is to explore the immune cells and immune-related gene expression in tumor microenvironment of CRC. Methods: CIBERSORT, a deconvolution algorithm, was used to analyze the infiltration of 22 immune cell types in the tumor microenvironment and immune-related gene expression in 404 CRC and 40 adjacent non-tumorous tissues. Results: a wide heterogeneity of immune cells among different paired tissues and in tumor stages was uncovered. M0 macrophages, M1 macrophages and CD4 memory activated T cells were infiltrated significantly more in CRC compared with normal tissues in both TCGA and GEO cohorts. CRC with T1-2 tumor stage showed increased CD4 memory activated T cells compared with T3-4 tumors. M0 macrophages were the highest in stage N1 tumors. Significant immune-related genes were identified to build prognostic models by Cox regression analysis. The concordance index of the prognostic model for TNM stage I-II was 0.69, and 0.71 for stage III-IV. The AUC values for 1-, 3-, and 5-year survivals were 0.674, 0.773, 0.812 for TNM stage I-II, respectively, and 0.764, 0.782, 0.803 for stage III-IV respectively. Conclusion: these results could assist clinicians in selecting targets for immunotherapies and individualize treatment strategies for patients with CRC.