Comprehensive analysis of tumor microenvironment landscape and potential therapeutic agents based on tumor-infiltrating immune cells in colorectal cancer

Abstract Background: Tumor-infiltrating immune cells (TIIC) are the major components of the tumor microenvironment (TME) and play vital roles in the tumorigenesis and progression of colorectal cancer (CRC). Increasing evidence has elucidated their significances in predicting prognosis and therapeutic efficacy. Nonetheless, the immune infiltrative landscape of CRC remains largely unknown. Methods: All the RNA-seq transcriptome data and full clinical annotation of 1213 colorectal cancer patients were downloaded from The Cancer Genome Atlas (TCGA) and Gene-Expression Omnibus (GEO) database. The “CIBERSORT” and “estimate” R package were applied to calculate 22 infiltrated immune cell fractions and stromal and immune score. Three TIIC patterns were determined by Unsupervised clustering methods. Through using principal-component analysis, TIIC scores were established. Data for potential agents comes from the Profiling Relative Inhibition Simultaneously in Mixtures (PRISM) and Cancer Therapeutics Response Portal database (CTRP). Results：In this study, we identified three distinct TIIC patterns characterized by distinct immunological features in 1213 CRC samples from multiple platforms. Base on the TIIC-related gene signatures from three clusters, we constructed a scoring system to quantify the immune infiltration level of individual samples in the CRC cohort and the clinical benefits of different groups. The high TIIC score group was marked by increased immune activation status and favorable prognosis. Conversely, low TIIC score group was featured with immune-desert phenotype and poor prognosis, along with the activation of transforming growth factor-β (TGF-β), WNT, ECM receptor interaction, and VEGF signaling pathways. Meanwhile, the high TIIC score group was also correlated with enhanced efficacy of immunotherapy. Additional, four chemotherapy drugs, seven CTRP-derived drug compounds and six PRISM-derived drug compounds were identified as potential drug for CRC among high and low TIIC subgroups.Conclusions: Collectively, as an effective prognostic biomarker and predictive indicator, the TIIC score plays an important role in the evaluation of CRC prognosis and the response of immunotherapy. Investigation of the TIIC patterns might provide us a promising target for improving immunotherapeutic efficacy in CRC.

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Identification of Tumor Microenvironment-related Prognostic Genes in Colorectal Cancer based on Bioinformatic Methods

10.21203/rs.3.rs-402277/v1 ◽

2021 ◽

Author(s):

Yi Liu ◽

Long Cheng ◽

Chao Li ◽

Chen Zhang ◽

Wang Lei ◽

...

Keyword(s):

Colorectal Cancer ◽

Tumor Microenvironment ◽

Immune Cell ◽

The Cancer Genome Atlas ◽

Cancer Prognosis ◽

Functional Enrichment ◽

Receptor Interaction ◽

Ppi Networks ◽

Chemokine Signaling ◽

Chemokine Signaling Pathway

Abstract Colorectal cancer (CRC) ranks fourth among the deadliest cancers globally, and the progression is highly affected by the tumor microenvironment (TME). This study explores the relationship between TME and colorectal cancer prognosis and identifies prognostic genes related to the CRC microenvironment. We collected the gene expression data from The Cancer Genome Atlas (TCGA) and calculated the scores of stromal/immune cells and their relations to clinical outcomes in colorectal cancer by the ESTIMATE algorithm. Lower immune scores were significantly related to malignant progression of CRC (stage, p=0.014; metastasis, p=0.001). We screened 292 differentially expressed genes (DEGs) by dividing CRC cases into high and low stromal/immune score groups. Functional enrichment analyses and protein-protein interaction (PPI) networks illustrated that these DEGs were closely involved in immune response, cytokine-cytokine receptor interaction, and chemokine signaling pathway. Six DEGs (FABP4, MEOX2, MMP12, ERMN, TNFAIP6, and CHST11) with prognostic value were identified by survival analysis and validated in an independent cohort (GSE17386). The six DEGs were significantly related to immune cell infiltration levels based on the Tumor Immune Estimation Resource (TIMER). The results might contribute to discovering new diagnostic and prognostic biomarkers and new treatment targets for colorectal cancer.

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Identification of tumor microenvironment-related prognostic genes in colorectal cancer based on bioinformatic methods

Scientific Reports ◽

10.1038/s41598-021-94541-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yi Liu ◽

Long Cheng ◽

Chao Li ◽

Chen Zhang ◽

Lei Wang ◽

...

Keyword(s):

Colorectal Cancer ◽

Tumor Microenvironment ◽

Immune Cell ◽

The Cancer Genome Atlas ◽

Cancer Prognosis ◽

Functional Enrichment ◽

Receptor Interaction ◽

Ppi Networks ◽

Chemokine Signaling ◽

Chemokine Signaling Pathway

AbstractColorectal cancer (CRC) ranks fourth among the deadliest cancers globally, and the progression is highly affected by the tumor microenvironment (TME). This study explores the relationship between TME and colorectal cancer prognosis and identifies prognostic genes related to the CRC microenvironment. We collected the gene expression data from The Cancer Genome Atlas (TCGA) and calculated the scores of stromal/immune cells and their relations to clinical outcomes in colorectal cancer by the ESTIMATE algorithm. Lower immune scores were significantly related to the malignant progression of CRC (metastasis, p = 0.001). We screened 292 differentially expressed genes (DEGs) by dividing CRC cases into high and low stromal/immune score groups. Functional enrichment analyses and protein–protein interaction (PPI) networks illustrated that these DEGs were closely involved in immune response, cytokine–cytokine receptor interaction, and chemokine signaling pathway. Six DEGs (FABP4, MEOX2, MMP12, ERMN, TNFAIP6, and CHST11) with prognostic value were identified by survival analysis and validated in two independent cohorts (GSE17538 and GSE161158). The six DEGs were significantly related to immune cell infiltration levels based on the Tumor Immune Estimation Resource (TIMER). The results might contribute to discovering new diagnostic and prognostic biomarkers and new treatment targets for colorectal cancer.

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492 Integration of high dimensional datasets in an immunocompetent mammary mouse model reveals pathways of tolerance and resistance to immune checkpoint blockade

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-sitc2020.0492 ◽

2020 ◽

Vol 8 (Suppl 3) ◽

pp. A528-A528

Author(s):

Lin Ma ◽

Jian-Hua Mao ◽

Mary Helen Barcellos-Hoff ◽

Jade Moore

Keyword(s):

Tumor Microenvironment ◽

Immune Cells ◽

Transforming Growth Factor ◽

Immune Cell ◽

Systemic Disease ◽

Ct Imaging ◽

High Dimensional ◽

Cytokine Signaling ◽

Immune Infiltrate ◽

Pet Ct

BackgroundCheckpoint inhibitors can induce robust and durable responses in a subset of patients. Extending this benefit to more patients could be facilitated by better understanding of how interacts with immune cells with the tumor microenvironment, which is a critical barrier to control both local and systemic disease. The composition and pattern of the immune infiltrate associates with the likelihood of response to immunotherapy. Inflamed tumors that exhibit a brisk immune cell infiltrate are responsive, while those in which immune cells are completely or partially excluded are not. Transforming growth factor β (TGFβ) is immunosuppressive and associated with the immune excluded phenotype.MethodsUsing an immune competent mammary tumor derived transplant (mTDT) model recently developed in our lab, exhibits inflamed, excluded or deserts immune infiltrate phenotypes based on localization of CD8 lymphocytes. Using whole transcriptome deep sequencing, cytof, and PET-CT imaging, we evaluated the tumor, microenvironment, and immune pathway activation among immune infiltrate phenotypes.ResultsThree distinct inflamed tumors phenotypes were identified: ‘classically’ inflamed characterized by pathway evidence of increased CD8+ T cells and decreased PD-L1 expression, inflamed tumors with pathways indicative of neovascularization and STAT3 signaling and reduced T cell mobilization, and an inflamed tumor with increased immunosuppressive myeloid phenotypes. Excluded tumors were characterized by TGFβ gene expression and pro-inflammatory cytokine signaling (e.g. TNFα, IL1β), associated with decreased leukocytes homing and increased immune cell death of cells. We visualized and quantified TGFβ activity using PET-CT imaging of 89Zr-fresolimumab, a TGFβ neutralizing antibody. TGFβ activity was significantly increased in excluded tumors compared to inflamed or desert tumors, which was supported by quantitative pathology (Perkin Elmer) of its canonical signaling target, phosphorylated SMAD2 (pSMAD2). pSMAD2 was positively correlated with PD-L1 expression in the stroma of excluded tumors. In contrast, in inflamed tumors, TGFβ activity positively correlated with increased F4/80 positive macrophages and negatively correlated with expression of PD-L1. CyTOF analysis of tumor and spleen immune phenotypes revealed increased trafficking of myeloid cells in mice bearing inflamed tumors compared to excluded and deserts.ConclusionsThe immunocompetent mTDT provides a model that bridges the gap between the immune landscape and tumor microenvironment. Integration of these high-dimensional data with further studies of response to immunotherapies will help to identify tumor features that favor response to treatment or the means to convert those that are unresponsive.

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Association of TGF-β expression with intratumoral infiltration of cytotoxic T lymphocytes in patients with microsatellite-stable colorectal cancer.

Journal of Clinical Oncology ◽

10.1200/jco.2019.37.15_suppl.3577 ◽

2019 ◽

Vol 37 (15_suppl) ◽

pp. 3577-3577

Author(s):

Amir Mehrvarz Sarshekeh ◽

Riham Katkhuda ◽

Anuj Verma ◽

Shailesh M Advani ◽

Michael J. Overman ◽

...

Keyword(s):

Colorectal Cancer ◽

Tumor Microenvironment ◽

T Lymphocytes ◽

Cytotoxic T Lymphocytes ◽

Immune Cells ◽

Transforming Growth Factor ◽

Molecular Subtype ◽

Rna Expression ◽

Continuous Variables ◽

Expression Levels

3577 Background: Transforming growth factor- β pathway (TGF-β) has an established role in promoting growth, invasion, metastasis as well as epithelial to mesenchymal (EMT) transition. Among 4 different described molecular subtypes of colorectal cancer (CRC), consensus molecular subtype 4 (CMS4) comprises up to 25% of CRC pts, distinguished by activation of this pathway, and is associated with higher relapse rate and poor prognosis. Recently, it has also been proposed that TGF-β activation drives immune evasion in murine models, but these findings have not been clinically validated. Methods: Using multi-gene RNA expression profiling, fresh-frozen paraffin-embedded samples of 35 patients with CRC were analyzed to determine TGF-β and EMT expression levels. Multiplexed IHC staining was performed on FFPE tumor blocks by using the Opal 7-Color fIHC Kit and the stained slides were scanned by a Vectra multispectral microscope (PerkinElmer) to measure infiltration of immune cells (i.e., T lymphocytes, cytotoxic T lymphocytes (CTL), T cell antigen-experienced, macrophages, etc.) in the tumor, stroma, and both components. TGF-β and EMT expression levels – as continuous variables - were compared with the infiltration of various immune cells using Spearman’s rank correlation analysis. Results: Among 35 pts, 28 pts had non-CMS1/MSS CRC. TGF-β RNA expression in the tumor microenvironment of these samples was inversely associated with the infiltration of CTL into the tumor (r=-0.43, p= 0.022). In contrast, there was no association of TGF-β with non-cytotoxic T-cells or macrophage infiltration. The tumor and stromal CTL infiltration differed substantially by CMS ( p=0.04, p=0.02, respectively) with tumor infiltration lowest in CMS4 (n=7). Consistent with this, EMT gene signature, which includes TGF-β expression, showed a similar inverse correlation with CTL infiltration (r=-0.48, p=0.009). Conclusions: TGF-β and EMT gene signatures have important roles in the exclusion of CTL in the tumor microenvironment of CRC pts. Inhibiting TGF-β pathway can potentially increase the intratumoral infiltration of CTL, which is a necessary (but not sufficient) step for immunotherapy response in MSS CRC. Clinical trials evaluating this hypothesis are currently ongoing (NCT03436563).

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SERPINE1 associated with remodeling of the tumor microenvironment in colon cancer progression: a novel therapeutic target

BMC Cancer ◽

10.1186/s12885-021-08536-7 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Shaokun Wang ◽

Li Pang ◽

Zuolong Liu ◽

Xiangwei Meng

Keyword(s):

Colorectal Cancer ◽

Colon Cancer ◽

Immune Cells ◽

Immune Cell ◽

Cox Regression ◽

Gene Set Enrichment Analysis ◽

The Cancer Genome Atlas ◽

Cell Infiltration ◽

Immune Cell Infiltration ◽

The Relationship

Abstract Background The change of immune cell infiltration essentially influences the process of colorectal cancer development. The infiltration of immune cells can be regulated by a variety of genes. Thus, modeling the immune microenvironment of colorectal cancer by analyzing the genes involved can be more conducive to the in-depth understanding of carcinogenesis and the progression thereof. Methods In this study, the number of stromal and immune cells in malignant tumor tissues were first estimated by using expression data (ESTIMATE) and cell-type identification with relative subsets of known RNA transcripts (CIBERSORT) to calculate the proportion of infiltrating immune cell and stromal components of colon cancer samples from the Cancer Genome Atlas database. Then the relationship between the TMN Classification and prognosis of malignant tumors was evaluated. Results By investigating differentially expressed genes using COX regression and protein-protein interaction network (PPI), the candidate hub gene serine protease inhibitor family E member 1 (SERPINE1) was found to be associated with immune cell infiltration. Gene Set Enrichment Analysis (GSEA) further projected the potential pathways with elevated SERPINE1 expression to carcinogenesis and immunity. CIBERSORT was subsequently utilized to investigate the relationship between the expression differences of SERPINE1 and immune cell infiltration and to identify eight immune cells associated with SERPINE1 expression. Conclusion We found that SERPINE1 plays a role in the remodeling of the colon cancer microenvironment and the infiltration of immune cells.

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A Novel Signature Constructed by Immune-Related LncRNA Predicts the Immune Landscape of Colorectal Cancer

Frontiers in Genetics ◽

10.3389/fgene.2021.695130 ◽

2021 ◽

Vol 12 ◽

Author(s):

Mengyu Sun ◽

Tongyue Zhang ◽

Yijun Wang ◽

Wenjie Huang ◽

Limin Xia

Keyword(s):

Colorectal Cancer ◽

High Risk ◽

Immune Cell ◽

Cox Regression ◽

Risk Group ◽

Univariate Analysis ◽

The Cancer Genome Atlas ◽

High Morbidity ◽

Cox Regression Analysis ◽

Chemotherapy Drugs

Colorectal cancer (CRC) has the characteristics of high morbidity and mortality. LncRNA not only participates in the progression of CRC through genes and transcription levels, but also regulates the tumor microenvironment and leads to the malignant phenotype of tumors. Therefore, we identified immune-related LncRNAs for the construction of clinical prognostic model. We searched The Cancer Genome Atlas (TCGA) database for original data. Then we identified differentially expressed irlncRNA (DEirlncRNA), which was paired and verified subsequently. Next, univariate analysis, Lasso and Cox regression analysis were performed on the DEirlncRNA pair. The ROC curve of the signature was drawn, and the optimal cut-off value was found. Then the cohort was divided into a high-risk and a low-risk group. Finally, we re-evaluated the signature from different perspectives. A total of 16 pairs of DEirlncRNA were included in the construction of the model. After regrouping according to the cut-off value of 1.275, the high-risk group showed adverse survival outcomes, progressive clinicopathological features, specific immune cell infiltration status, and high sensitivity to some chemotherapy drugs. In conclusion, we constructed a signature composed of immune-related LncRNA pair with no requirement of the specific expression level of genes, which shows promising clinical predictive value in CRC patients.

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Effects of Hypoxia in Intestinal Tumors on Immune Cell Behavior in the Tumor Microenvironment

10.21203/rs.3.rs-131685/v1 ◽

2020 ◽

Author(s):

Luping Zhang ◽

Shaokun Wang ◽

Yachen Wang ◽

Weidan Zhao ◽

Yingli Zhang ◽

...

Keyword(s):

Colorectal Cancer ◽

Tumor Microenvironment ◽

Risk Score ◽

Immune Cell ◽

Risk Groups ◽

Low Risk ◽

Computational Method ◽

Gene Set Enrichment Analysis ◽

The Cancer Genome Atlas ◽

Cell Behavior

Abstract Background: Imbalanced nutritional supply and demand in the tumor microenvironment often leads to hypoxia. The subtle interaction between hypoxia and immune cell behavior plays an important role in tumor occurrence and development. However, the functional relationship between hypoxia and the tumor microenvironment remains unclear. Therefore, we aimed to investigate the effect of hypoxia on the intestinal tumor microenvironment.Method: We extracted the names of hypoxia-related genes from the Gene Set Enrichment Analysis (GSEA) database and screened them for those associated with the prognosis of colorectal cancer, with the final list including ALDOB, GPC1, ALDOC, and SLC2A3. Using the sum of the expression levels of these four genes, provided by The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, and the expression coefficients, we developed a hypoxia risk score model. Using the median risk score value, we divided the patients in the two databases into high- and low-risk groups.GSEA was used to compare the enrichment differences between the two groups.We used the CIBERSORT computational method to analyze immune cell infiltration.Finally,the correlation between these five genes and hypoxia was analyzed. Result: The prognosis of the two groups differed significantly, with a higher survival rate in the low-risk group than in the high-risk group.We found that the different risk groups were enriched by immune-related and inflammatory pathways. We identified activated CD4 memory T cells and M0 macrophages in TCGA and GEO databases and found that CCL2/4/5, CSF1, and CX3CL1 contributed toward the increased infiltration rate of these immune cell types. Finally, we observed a positive correlation between the five candidate genes’ expression and the risk of hypoxia, with significant differences in the level of expression of each of these genes between patient risk groups.Conclusion: Overall, our data suggest that hypoxia is associated with the prognosis and rate of immune system infiltration in patients with colorectal cancer. This finding may improve immunotherapy for colorectal cancer.

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INHBB Is a Novel Prognostic Biomarker Associated with Cancer-Promoting Pathways in Colorectal Cancer

BioMed Research International ◽

10.1155/2020/6909672 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Jinpeng Yuan ◽

Aosi Xie ◽

Qiangjian Cao ◽

Xinxin Li ◽

Juntian Chen

Keyword(s):

Colorectal Cancer ◽

Signaling Pathways ◽

Signaling Pathway ◽

Transforming Growth Factor ◽

Cox Regression ◽

Prognostic Biomarker ◽

Disease Free Survival ◽

Gene Set Enrichment Analysis ◽

The Cancer Genome Atlas ◽

Receptor Interaction

Background. Inhibin subunit beta B (INHBB) is a protein-coding gene that participated in the synthesis of the transforming growth factor-β (TGF-β) family members. The study is aimed at exploring the clinical significance of INHBB in patients with colorectal cancer (CRC) by bioinformatics analysis. Methods. Real-time PCR and analyses of Oncomine, Gene Expression Omnibus (GEO), and The Cancer Genome Atlas (TCGA) databases were utilized to evaluate the INHBB gene transcription level of colorectal cancer (CRC) tissue. We evaluated the INHBB methylation level and the relationship between expression and methylation levels of CpG islands in CRC tissue. The corresponding clinical data were obtained to further explore the association of INHBB with clinical and survival features. In addition, Gene Set Enrichment Analysis (GSEA) was performed to explore the gene ontology and signaling pathways of INHBB involved. Results. INHBB expression was elevated in CRC tissue. Although the promoter of INHBB was hypermethylated in CRC, methylation did not ultimately correlate with the expression of INHBB. Overexpression of INHBB was significantly and positively associated with invasion depth, distant metastasis, and TNM stage. Cox regression analyses and Kaplan-Meier survival analysis indicated that high expression of INHBB was correlated with worse overall survival (OS) and disease-free survival (DFS). GSEA showed that INHBB was closely correlated with 5 cancer-promoting signaling pathways including the Hedgehog signaling pathway, ECM receptor interaction, TGF-β signaling pathway, focal adhesion, and pathway in cancer. INHBB expression significantly promoted macrophage infiltration and inhibited memory T cell, mast cell, and dendritic cell infiltration. INHBB expression was positively correlated with stromal and immune scores of CRC samples. Conclusion. INHBB might be a potential prognostic biomarker and a novel therapeutic target for CRC.

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The possible role of SRMS in colorectal cancer by bioinformatics analysis

World Journal of Surgical Oncology ◽

10.1186/s12957-021-02431-y ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Jie Zhang ◽

Weidong Liu ◽

Sisi Feng ◽

Baiyun Zhong

Keyword(s):

Colorectal Cancer ◽

Immune Cell ◽

Enrichment Analysis ◽

The Cancer Genome Atlas ◽

Receptor Interaction ◽

Marker Genes ◽

Cell Marker ◽

Translational Initiation ◽

Expression Levels

Abstract Background Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites (SRMS) is a non-receptor tyrosine kinase that has been found to be overexpressed in various tumors. However, the role of SRMS in colorectal cancer (CRC) has not been well established. Methods We evaluated the expression levels of SRMS in CRC using GEPIA, Oncomine, and HPA datasets. Survival information and gene expression data of CRC were obtained from The Cancer Genome Atlas (TCGA). Then, the association between SRMS and clinicopathological features was analyzed using UALCAN dataset. LinkedOmics was used to determine co-expression and functional networks associated with SRMS. Besides, we used TISIDB to assess the correlation between SRMS and immune signatures, including tumor-infiltrating immune cells and immunomodulators. Lastly, protein-protein interaction network (PPI) was established and the function enrichment analysis of the SRMS-associated immunomodulators and immune cell marker genes were performed using the STRING portal. Results Compared to normal colorectal tissues, SRMS was found to be overexpressed in CRC tissues, which was correlated with a poor prognosis. In colon adenocarcinoma (COAD), the expression levels of SRMS are significantly correlated with pathological stages and nodal metastasis status. Functional network analysis suggested that SRMS regulates intermediate filament-based processes, protein autophosphorylation, translational initiation, and elongation signaling through pathways involving ribosomes, proteasomes, oxidative phosphorylation, and DNA replication. In addition, SRMS expression was correlated with infiltrating levels of CD4+ T cells, CD56dim, MEM B, Neutrophils, Th2, Th17, and Act DC. The gene ontology (GO) analysis of SRMS-associated immunomodulators and immune cell marker genes showed that they were mainly enriched in the immune microenvironment molecule-related signals. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of these genes indicated that they are involved in multiple cancer-related pathways. Conclusions SRMS is a promising prognostic biomarker and potential therapeutic target for CRC patients. In particular, SRMS regulates CRC progression by modulating cytokine-cytokine receptor interaction, chemokines, IL-17, and intestinal immune networks for IgA production signaling pathways among others. However, more studies are needed to validate these findings.

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Crosstalk between the MSI status and tumor microenvironment in colorectal cancer.

Journal of Clinical Oncology ◽

10.1200/jco.2020.38.15_suppl.e15236 ◽

2020 ◽

Vol 38 (15_suppl) ◽

pp. e15236-e15236

Author(s):

Peng Luo ◽

Anqi Lin ◽

Jian Zhang

Keyword(s):

Colorectal Cancer ◽

Tumor Microenvironment ◽

Microsatellite Instability ◽

Immune Cell ◽

The Cancer Genome Atlas ◽

Cell Infiltration ◽

Immune Cell Infiltration ◽

Immune Microenvironment ◽

Mutation Data ◽

Immune Related Genes

e15236 Background: In recent years, cancer immunotherapy has been extensively studied, and colorectal cancer (CRC) patients have also derived clinical benefits from immunotherapy, especially CRC patients with mismatch repair deficiency (dMMR)/microsatellite instability-high (MSI-H), whose sensitivity to immune checkpoint inhibitors (ICIs) is significantly higher than that of patients with microsatellite-stable (MSS)/microsatellite instability-low (MSI-L) disease. This study suggests that patients with MSI-H CRC have a higher mutational burden and more immune cell infiltration than those with MSS/MSI-L disease. However, most studies have not systematically evaluated the immune characteristics and immune microenvironments of MSI-H and MSS/MSI-L CRC. Methods: A published CRC cohort with mutation and immunotherapy-related prognostic data was collected. We analyzed the relationship between the MSI status and prognosis of ICI treatment in an immunotherapy cohort. We then further used mutation data for the immunotherapy and The Cancer Genome Atlas (TCGA)-CRC (colon adenocarcinoma (COAD) + rectum adenocarcinoma (READ) cohorts. For mRNA expression, mutation data analysis of the immune microenvironment and immunogenicity under different MSI status was performed. Results: Compared with MSS/MSI-L CRC patients, patients with MSI-H CRC significantly benefited from ICI treatment. We found that MSI-H CRC had more immune cell infiltration, higher expression of immune-related genes and higher immunogenicity than MSS/MSI-L disease. The MANTIS score used to predict the MSI status was positively correlated with immune cells, immune-related genes, and immunogenicity. In addition, subtype analysis showed that COAD and READ might have different tumor immune microenvironments. Conclusions: MSI-H CRC may have an inflammatory tumor microenvironment and increased sensitivity to ICIs. Unlike those of MSI-H READ, the immune characteristics of MSI-H COAD may be consistent with those of MSI-H CRC. Furthermore, the possible mechanism underlying the prognostic differences among CRC patients receiving ICIs in relation to the immune microenvironment were elucidated to provide theoretical guidance for further improving the curative effect of ICIs treatment on MSI-H CRC patients in the future and solve the problems underlying why MSS/MSI-L CRC patients do not benefit from ICIs treatment.

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