Colorectal Cancer Microenvironment Research Articles

Colorectal Cancer-Derived Exosomes Impair CD4+ T Cell Function and Accelerate Cancer Progression via Macrophage Activation.

Background: Exosomal programmed death ligand 1 (PD-L1), an exosomal membrane protein found in many tumor types, is reckoned to help regulate the immune microenvironment. However, the functions and the mechanisms underlying the exosome-mediated regulation of the immune microenvironment in colorectal cancer (CRC) remain unknown. Methods: Western blotting was used to investigate the levels of exosomal PD-L1 in the peripheral blood of patients with CRC and healthy controls. A CRC mouse model was constructed by administering 10 mg/kg azoxymethane (AOM) and dextrane sodium sulfate (DSS) intraperitoneally. The mice were then administered the control or CRC-derived exosomes to examine the regulatory effect of the exosomes on macrophage infiltration and CRC development. In vitro studies, using a coculture system, and flow cytometry analysis were conducted to examine the relationship between the regulatory effect of CRC-derived exosomes on CD4+ T cells and tumor-associated macrophages. RNA-seq and reverse transcription-quantitative polymerase chain reaction assays were used to investigate the mechanisms underlying the regulatory effect of the CRC-derived exosomes on macrophage proliferation and the regulation of the immune microenvironment during CRC development. Results: In patients with CRC, higher levels of exosomal PD-L1 were associated with a more severe form of disease. The treatment of mice with AOM/DSS-induced CRC with CRC-derived exosomes resulted in high levels of macrophage proliferation, increased PD-L1 levels in macrophages, and accelerated CRC progression. Importantly, analysis of an in vitro coculture system and flow cytometry analysis showed that the CRC-derived exosomes transported PD-L1 into macrophages and impaired CD4+ T cell function. Preliminary data suggest that the NF-κb signaling pathway regulates the function of CRC-derived exosomal PD-L1-dependent macrophages. Conclusion: CRC-derived exosomes induce the proliferation of macrophages and increase their PD-L1 levels. They also impair CD4+ T cell function and promote CRC progression. Our findings reveal a novel exosomal PD-L1-mediated crosstalk between the CRC cells and immune cells in the CRC microenvironment.

Identification of PFKFB3 as a key factor in the development of colorectal cancer and immunotherapy resistance

Resistance to immunotherapy poses a significant challenge in the treatment of colorectal cancer (CRC), and the underlying mechanisms are not fully understood. Recent studies have implicated PFKFB3, a crucial glycolytic enzyme, in shaping the tumor microenvironment in CRC. Our study aimed to systematically study the role of PFKFB3 in CRC. Bioinformatic analysis revealed that PFKFB3 expression is notably elevated in CRC tissues compared to normal counterparts. In vivo experiments confirmed that suppressing PFKFB3 reduces the tumorigenesis of CRC. We identified multiple cancer-associated pathways positively correlated with high expression of PFKFB3, such as epithelial-mesenchymal transition (EMT), hypoxia, KRAS signaling, angiogenesis, PI3K/AKT/mTOR, Hedgehog, and Notch pathways. Additionally, PFKFB3 exhibited significant correlations with various immune-related pathways, including complement, IL-2/STAT5, IL-6/JAK/STAT3, IFN-α/IFN-γ, TGF-β, and TNF-α/NF-κB, as well as several immunosuppressive cell markers found in regulatory T cells (CCR8, TGFB1, STAT5B, FOXP3), M2 macrophages (CD163, VSIG4, MS4A4A), T cell exhaustion markers (CTLA-4, PDCD1, LAG3), and PD-L1. Intriguingly, increased PFKFB3 expression was observed in PD-L1 blockade-resistant patients and was associated with shorter overall survival. In a nutshell, PFKFB3 plays an important role in CRC tumorigenesis and resistance to immunotherapy. Targeting PFKFB3 inhibits tumor formation and enhances the efficacy of immunotherapy. Our findings underscore the functions of PFKFB3 in CRC, shedding light on both cancer-related and immunosuppressive pathways.

547P Artificial Intelligence-powered analysis of the tumor immune microenvironment in primary and metastatic colorectal cancer

547P Artificial Intelligence-powered analysis of the tumor immune microenvironment in primary and metastatic colorectal cancer

The current role of dendritic cells in the progression and treatment of colorectal cancer.

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related deaths worldwide. Dendritic cells (DCs) constitute a heterogeneous group of antigen-presenting cells that are important for initiating and regulating both innate and adaptive immune responses. As a crucial component of the immune system, DCs have a pivotal role in the pathogenesis and clinical treatment of CRC. DCs cross-present tumor-related antigens to activate T cells and trigger an antitumor immune response. However, the antitumor immune function of DCs is impaired and immune tolerance is promoted due to the presence of the tumor microenvironment. This review systematically elucidates the specific characteristics and functions of different DC subsets, as well as the role that DCs play in the immune response and tolerance within the CRC microenvironment. Moreover, how DCs contribute to the progression of CRC and potential therapies to enhance antitumor immunity on the basis of existing data are also discussed, which will provide new perspectives and approaches for immunotherapy in patients with CRC.

ETS1 Deficiency in Macrophages Suppresses Colorectal Cancer Progression by Reducing the F4/80+TIM4+ Macrophage Population.

Tumor-associated macrophages (TAMs) take on pivotal and complex roles in the tumor microenvironment (TME); however, their heterogeneity in the TME remains incompletely understood. ETS proto-oncogene 1 (ETS1) is a transcription factor that is mainly expressed in lymphocytes. However, its expression and immunoregulatory role in colorectal cancer (CRC)-associated macrophages remain unclear. In the study, the expression levels of ETS1 in CD68+ macrophages in the CRC microenvironment were significantly higher than those in matched para-carcinoma tissues. Importantly, ETS1 increased the levels of chemokines C-C motif chemokine ligand 2 (CCL2) and C-X-C motif chemokine ligand 10 (CXCL10) in lipopolysaccharide-stimulated THP-1 cells. It also boosted the migration and invasion of CRC cells during the in vitro co-culture. In ETS1 conditional knockout mouse model, ETS1 deficiency in macrophages ameliorated the histological changes in DSS-induced ulcerative colitis mouse models and prolonged the survival in an azomethane/dextran sodium sulfate (AOM/DSS)-induced CRC model. ETS1 deficiency in macrophages substantially inhibited tumor formation, reduced F4/80+TIM4+ macrophages in the mesenteric lymph nodes, and decreased CCL2 and CXCL10 protein levels in tumor tissues. Moreover, ETS1 deficiency in macrophages effectively prevented liver metastasis of CRC and reduced the infiltration of TAMs into the metastasis sites. Subsequent studies have indicated that ETS1 upregulated the expression of T-cell immunoglobulin mucin receptor 4 in macrophages through the signal transducer and activator of transcription 1 signaling pathway activated by the autocrine action of CCL2/CXCL10. Collectively, ETS1 deficiency in macrophages potentiates antitumor immune responses by repressing CCL2 and CXCL10 expression, shedding light on potential therapeutic strategies for CRC.

Research progress on the effect of pyroptosis on the occurrence, development, invasion and metastasis of colorectal cancer

Pyroptosis is a type of programmed cell death mediated by gasdermines (GSDMs). The N-terminal domain of GSDMs forms pores in the plasma membrane, causing cell membrane rupture and the release of cell contents, leading to an inflammatory response and mediating pyrodeath. Pyroptosis plays an important role in inflammatory diseases and malignant tumors. With the further study of pyroptosis, an increasing number of studies have shown that the pyroptosis pathway can regulate the tumor microenvironment and antitumor immunity of colorectal cancer and is closely related to the occurrence, development, treatment and prognosis of colorectal cancer. This review aimed to explore the molecular mechanism of pyroptosis and the role of pyroptosis in the occurrence, development, treatment and prognosis of colorectal cancer (CRC) and to provide ideas for the clinical diagnosis and treatment of CRC.

Fusobacterium nucleatum, immune responses, and metastatic organ diversity in colorectal cancer liver metastasis.

The presence of Fusobacterium nucleatum is associated with an immunosuppressive tumor immune microenvironment (TIM) in primary colorectal cancer (CRC), contributing to tumor progression. Its persistence in CRC liver metastasis tissues raises questions about its role in modulating local and systemic immune responses and influencing recurrence patterns. This retrospective cohort study of 218 patients with CRC liver metastasis investigated the association of F. nucleatum in CRC liver metastasis tissues with systemic inflammation, TIM alterations, and the number of metastatic organs involved in recurrence. Two-step polymerase chain reaction (PCR), including digital PCR, detected F. nucleatum in 42% (92/218) of fresh-frozen specimens of CRC liver metastases. Compared with the F. nucleatum-none group, the F. nucleatum-high group showed higher C-reactive protein levels (0.82 vs. 0.22 mg/dL; Ptrend = 0.02), lower numbers of CD8+ cells (33.2 vs. 65.3 cells/mm2; Ptrend = 0.04) and FOXP3+ cells (11.3 vs. 21.7 cells/mm2; Ptrend = 0.01) in the TIM, and a greater number of metastatic organs involved in recurrence (1.6 vs. 1.1; p < 0.001). The presence of F. nucleatum in CRC liver metastasis tissues was associated with increased systemic inflammation, TIM alterations, and a greater number of metastatic organs involved in recurrence. These findings suggest a potential contribution of F. nucleatum to the metastatic propensity of CRC cells and could inform future research to enhance understanding of the interaction between tumor, host, and microbes in the metastatic process.

ASIC3-activated key enzymes of de novo lipid synthesis supports lactate-driven EMT and the metastasis of colorectal cancer cells

Acidic microenvironments is a cancer progression driver, unclear core mechanism hinders the discovery of new diagnostic or therapeutic targets. ASIC3 is an extracellular proton sensor and acid-sensitive, but its role in acidic tumor microenvironment of colorectal cancer is not reported. Functional analysis data show that colorectal cancer cells respond to specific concentration of lactate to accelerate invasion and metastasis, and ASIC3 is the main actor in this process. Mechanism reveal de novo lipid synthesis is a regulatory process of ASIC3, down-regulated ASIC3 increases and interacts with ACC1 and SCD1, which are key enzymes in de novo lipid synthesis pathway, this interaction results in increased unsaturated fatty acids, which in turn induce EMT to promote metastasis, and overexpression of ASIC3 reduces acidic TME-enhanced colorectal cancer metastasis. Clinical samples of colorectal cancer also exhibit decreased ASIC3 expression, and low ASIC3 expression is associated with metastasis and stage of colorectal cancer. This study is the first to identify the role of the ASIC3-ACC1/SCD1 axis in acid-enhanced colorectal cancer metastasis. The expression pattern of ASIC3 in colorectal cancer differs significantly from that in other types of cancers, ASIC3 may serve as a novel and reliable marker for acidic microenvironmental in colorectal cancer, and potentially a therapeutic target.

Potential regulation and prognostic model of colorectal cancer with extracellular matrix genes

BackgroundThe tumor microenvironment (TME) of colorectal cancer (CRC) mainly comprises immune cells, stromal cells, tumor cells, as well as the extracellular matrix (ECM), which holds a pivotal position. The ECM affects cancer progression, but its regulatory roles and predictive potential in CRC are not fully understood. MethodsWe analyzed transcriptomes from CRC tumors and paired normal tissues to study ECM features. Up-regulated ECM components were examined through functional enrichment analysis, and single-cell sequencing identified cell types producing collagen, regulators, and secreted factors. Transcription factor analysis and cell-cell interaction studies were conducted to identify potential regulators of ECM changes. Additionally, a prognostic model was developed using TCGA-CRC cohort data, focusing on up-regulated core ECM components. ResultsBulk RNA-seq analysis revealed a unique ECM pattern in tumors, with ECM abundance and composition significantly related to patient survival. Up-regulated ECM components were linked to various cancer-related pathways. Fibroblasts and non-fibroblasts interactions were crucial in forming the TME. Key potential regulators identified included ZNF469, PRRX2, TWIST1, and AEBP1. A prognostic model based on five ECM genes (THBS3, LAMB3, ESM1, SPRX, COL9A3) demonstrated strong associations with immune suppression and tumor angiogenesis. ConclusionsThe ECM components were involved in various cell-cell interactions and correlated with tumor development and poor survival outcomes. The ECM prognostic model components could be potential targets for novel therapeutic interventions in colorectal cancer.

The Role of Adipocytes Recruited as Part of Tumor Microenvironment in Promoting Colorectal Cancer Metastases.

Adipose tissue dysfunction, which is associated with an increased risk of colorectal cancer (CRC), is a significant factor in the pathophysiology of obesity. Obesity-related inflammation and extracellular matrix (ECM) remodeling promote colorectal cancer metastasis (CRCM) by shaping the tumor microenvironment (TME). When CRC occurs, the metabolic symbiosis of tumor cells recruits adjacent adipocytes into the TME to supply energy. Meanwhile, abundant immune cells, from adipose tissue and blood, are recruited into the TME, which is stimulated by pro-inflammatory factors and triggers a chronic local pro-inflammatory TME. Dysregulated ECM proteins and cell surface adhesion molecules enhance ECM remodeling and further increase contractibility between tumor and stromal cells, which promotes epithelial-mesenchymal transition (EMT). EMT increases tumor migration and invasion into surrounding tissues or vessels and accelerates CRCM. Colorectal symbiotic microbiota also plays an important role in the promotion of CRCM. In this review, we provide adipose tissue and its contributions to CRC, with a special emphasis on the role of adipocytes, macrophages, neutrophils, T cells, ECM, and symbiotic gut microbiota in the progression of CRC and their contributions to the CRC microenvironment. We highlight the interactions between adipocytes and tumor cells, and potential therapeutic approaches to target these interactions.

Myeloid‑derived suppressor cells: Key immunosuppressive regulators and therapeutic targets in colorectal cancer (Review).

Globally, colorectal cancer (CRC) is the third most common type of cancer. CRC has no apparent symptoms in the early stages of disease, and most patients receive a confirmed diagnosis in the middle or late disease stages. The incidence of CRC continues to increase, and the affected population tends to be younger. Therefore, determining how to achieve an early CRC diagnosis and treatment has become a top priority for prolonging patient survival. Myeloid‑derived suppressor cells (MDSCs) are a group of bone marrow‑derived immuno‑negative regulatory cells that are divided into two subpopulations, polymorphonuclear‑MDSCs and monocytic‑MDSCs, based on their phenotypic similarities to neutrophils and monocytes, respectively. These cells can inhibit the immune response and promote cancer cell metastasis in the tumour microenvironment (TME). A large aggregation of MDSCs in the TME is often a marker of cancer and a poor prognosis in inflammatory diseases of the intestine (such as colonic adenoma and ulcerative colitis). In the present review, the phenotypic classification of MDSCs in the CRC microenvironment are first discussed. Then, the amplification, role and metastatic mechanism of MDSCs in the CRC TME are described, focusing on genes, gene modifications, proteins and the intestinal microenvironment. Finally, the progress in CRC‑targeted therapies that aim to modulate the quantity, function and structure of MDSCs are summarized in the hope of identifying potential screening markers for CRC and improving CRC prognosis and therapeutic options.

Ubiquitin-Specific Protease 52 as a Prognostic Biomarker Correlates with Tumor Microenvironment and Therapy Response in Colorectal Cancer.

As the primary members of the deubiquitinase family, ubiquitin-specific proteases can regulate the efficacy of immunotherapy and mediate immune evasion. However, further research is needed to explore the influence of USP52 on the prognosis of colorectal cancer (CRC), the tumor immune microenvironment, and therapeutic response. The differential expression of USP52 between CRC and normal tissues was analyzed using multiple public databases. The relationship between USP52 with the prognosis and clinicopathological characteristics of CRC patients was evaluated, and a nomogram was constructed to predict patient survival based on USP52 expression. Subsequently, gene set variation analysis (GSVA) was used to explore the potential biological functions of USP52 in CRC. The impact of USP52 on the tumor microenvironment (TME) was estimated. Moreover, the effect of USP52 on the response to immunotherapy and chemotherapeutic drugs in CRC was investigated. Finally, the correlation between tumor mutation burden (TMB)/microsatellite instability (MSI) status and USP52 was explored. The expression of USP52 was markedly upregulated in CRC, correlating with a poor prognosis in patients. GSVA uncovered a strong association between high USP52 and immune suppression. Furthermore, high USP52 was found to be correlated with a non-inflamed TME, resulting in reduced immune cell infiltration levels. Additionally, it was observed that patients with high USP52 exhibited low sensitivity to both immunotherapy and chemotherapeutic drugs. Lastly, high USP52 was negatively associated with high TMB and MSI. This study revealed the significance of USP52 in TME, efficacy of therapy, and clinical prognosis in CRC, offering novel insights for the therapeutic advancements in CRC.

High-confidence calling of normal epithelial cells allows identification of a novel stem-like cell state in the colorectal cancer microenvironment.

Single-cell analyses can be confounded by assigning unrelated groups of cells to common developmental trajectories. For instance, cancer cells and admixed normal epithelial cells could adopt similar cell states thus complicating analyses of their developmental potential. Here, we develop and benchmark CCISM (for Cancer Cell Identification using Somatic Mutations) to exploit genomic single nucleotide variants for the disambiguation of cancer cells from genomically normal non-cancer cells in single-cell data. We find that our method and others based on gene expression or allelic imbalances identify overlapping sets of colorectal cancer versus normal colon epithelial cells, depending on molecular characteristics of individual cancers. Further, we define consensus cell identities of normal and cancer epithelial cells with higher transcriptome cluster homogeneity than those derived using existing tools. Using the consensus identities, we identify significant shifts of cell state distributions in genomically normal epithelial cells developing in the cancer microenvironment, with immature states increased at the expense of terminal differentiation throughout the colon, and a novel stem-like cell state arising in the left colon. Trajectory analyses show that the new cell state extends the pseudo-time range of normal colon stem-like cells in a cancer context. We identify cancer-associated fibroblasts as sources of WNT and BMP ligands potentially contributing to increased plasticity of stem cells in the cancer microenvironment. Our analyses advocate careful interpretation of cell heterogeneity and plasticity in the cancer context and the consideration of genomic information in addition to gene expression data when possible.

Systematic Analysis of Human Colorectal Cancer scRNA-seq Revealed Limited Pro-tumoral IL-17 Production Potential in Gamma Delta T Cells.

Gamma delta (γδ) T cells play a crucial role in anti-tumor immunity due to their cytotoxic properties. However, the role and extent of γδ T cells in production of pro-tumorigenic interleukin- 17 (IL-17) within the tumor microenvironment (TME) of colorectal cancer (CRC) remains controversial. In this study, we re-analyzed nine published human CRC whole-tissue single-cell RNA sequencing (scRNA-seq) datasets, identifying 18,483 γδ T cells out of 951,785 total cells, in the neoplastic or adjacent normal tissue of 165 human CRC patients. Our results confirm that tumor-infiltrating γδ T cells exhibit high cytotoxicity-related transcription in both tumor and adjacent normal tissues, but critically, none of the γδ T cell clusters showed IL-17 production potential. We also identified various γδ T cell subsets, including Teff, TRM, Tpex, and Tex, and noted an increased expression of cytotoxic molecules in tumor-infiltrating γδ T cells compared to their normal area counterparts. Our work demonstrates that γδ T cells in CRC primarily function as cytotoxic effector cells rather than IL-17 producers, mitigating the concerns about their potential pro-tumorigenic roles in CRC, highlighting the importance of accurately characterizing these cells for cancer immunotherapy research and the unneglectable cross-species discrepancy between the mouse and human immune system in the study of cancer immunology.

Exploring lidocaine’s cytostatic effects and modulation of the tumour microenvironment in colorectal cancer

Exploring lidocaine’s cytostatic effects and modulation of the tumour microenvironment in colorectal cancer

MiRNAs: possible regulators of toll like receptors and inflammatory tumor microenvironment in colorectal cancer

BackgroundColorectal cancer (CRC) is ranked as the third most commonly diagnosed cancer and the third cause of cancer related deaths. CRC is greatly attributed to genetic and epigenetic mutations and immune dysregulation. Tumor aberrant expression of Toll-like Receptors (TLRs) can contribute to tumorigenesis. Recent studies suggested that microRNAs act as direct ligands of TLRs altering their expression and signaling pathways.AimTo prove our concept that specific miRNA mimics may act as antagonists of their specific toll like receptors inhibiting their expression that could limit the release of pro-inflammatory and pro-tumorigenic cytokines leading to apoptosis of tumor cells.MethodsFrom public microarray databases, we retrieved TLRs and miRNAs related to CRC followed by in silico docking of the selected miRNA ligands into the TLRs. Clinical validation after co-immunoprecipitation of TLRs and their interacting miRNA ligands was done. Expression of TLRs 1, 7,8 was determined by ELISA while miRNAs was measured by RT-qPCR. In addition, microRNA mimics of the down regulated miRNAs were transfected into human CRC cell lines.ResultsOur data demonstrate that TLRs 1, 7, 8 are up regulated in CRC compared to controls. Further, three miRNAs (-122, -29b and -15b) are relatively downregulated, while 4 miRNAs (-202, miRNA-98, -21 and -let7i) are upregulated in CRC patients compared to those with benign tumor and healthy controls. Transfection of down regulated miRNA mimics into CRC cell lines resulted in a significant reduction of the number and viability of cells as well as down regulating the expression of TLRs 1, 7 and 8 with ultimate reduction of downstream effector IL6 protein, suggesting that these miRNAs are negative regulators of carcinogenesis.ConclusionMicroRNAs could act as antagonistic ligands of TLRs limiting the inflammatory tumor microenvironment.

Single-cell immune escape correlation analysis: unraveling the prognostic influence of intercellular communication in the tumor microenvironment of colorectal cancer

Single-cell immune escape correlation analysis: unraveling the prognostic influence of intercellular communication in the tumor microenvironment of colorectal cancer

Multifunctional Nanodrug‐Mediated Immunotherapy in Microsatellite Stable Colorectal Cancer via Promoting m6A Modification and M1‐Like Tumor‐Associated Macrophages Polarization

Immunotherapy has made great progress in various solid tumors. However, the “cold” tumor immune microenvironment of microsatellite stable subtype colorectal cancer (MSS‐CRC) hinders the effectiveness of immunotherapy. Therefore, reshaping the immunosuppressive microenvironment and initiating efficient antitumor immune responses are critical for immunotherapy of MSS‐CRC. According to the analysis of clinical samples, it is found that the levels of fat mass and obesity‐associated protein (FTO) and M2‐like tumor‐associated macrophages (TAMs) infiltration are significantly elevated in CRC tissue, which has driven one to construct a targeted cationic liposome to simultaneously enhance the RNA methylation and inhibit the CD47 immune checkpoint expression of tumor cells in the hope of promoting the M1‐like TAMs polarization and phagocytosis. By upregulating the m6A modification of tumor cells, the lactate secretion is decreased to promote the TAMs repolarized into M1‐like. Meanwhile, CD47 siRNA codelivered by the cationic liposomes downregulates the expression of immune checkpoint CD47 on the cancer cell surface, which enhances the phagocytic ability of the M1‐like TAMs. The combination treatment scheme is expected to provide a new option for treating MSS‐CRC, which may also be extended for treating other immunologically “cold” tumors.

Dual inhibitors of DNMT and HDAC remodels the immune microenvironment of colorectal cancer and enhances the efficacy of anti-PD-L1 therapy

Colorectal cancer is the second most prevalent and deadly cancer worldwide. The emergence of immune checkpoint therapy has provided a revolutionary strategy for the treatment of solid tumors. However, less than 5 % of colorectal cancer patients respond to immune checkpoint therapy. Thus, it is of great scientific significance to develop “potentiators” for immune checkpoint therapy. In this study, we found that knocking down different DNMT and HDAC isoforms could increase the expression of IFNs in colorectal cancer cells, which can enhance the effectiveness of immune checkpoint therapy. Therefore, the combined inhibition of DNMT and HDAC cloud synergistically enhance the effect of immunotherapy. We found that dual DNMT and HDAC inhibitors C02S could inhibit tumor growth in immunocompetent mice but not in immunocompromised nude mice, which indicates that C02S exerts its antitumor effects through the immune system. Mechanistically, C02S could increase the expression of ERVs, which generated the intracellular levels of dsRNA in tumor cells, and then promotes the expression of IFNs through the RIG-I/MDA5-MAVS signaling pathway. Moreover, C02S increased the immune infiltration of DCs and T cells in microenvironment, and enhanced the efficacy of anti-PD-L1 therapy in MC38 and CT26 mice model. These results confirmed that C02S can activate IFNs through the RIG-I/MDA5-MAVS signaling pathway, remodel the tumor immune microenvironment and enhance the efficacy of immune checkpoint therapy, which provides new evidence and solutions for the development of “potentiator” for colorectal cancer immunotherapy.

Action of circulating and infiltrating B cells in the immune microenvironment of colorectal cancer by single-cell sequencing analysis.

The complexity of the immune microenvironment has an impact on the treatment of colorectal cancer (CRC), one of the most prevalent malignancies worldwide. In this study, multi-omics and single-cell sequencing techniques were used to investigate the mechanism of action of circulating and infiltrating B cells in CRC. By revealing the heterogeneity and functional differences of B cells in cancer immunity, we aim to deepen our understanding of immune regulation and provide a scientific basis for the development of more effective cancer treatment strategies. To explore the role of circulating and infiltrating B cell subsets in the immune microenvironment of CRC, explore the potential driving mechanism of B cell development, analyze the interaction between B cells and other immune cells in the immune microenvironment and the functions of communication molecules, and search for possible regulatory pathways to promote the anti-tumor effects of B cells. A total of 69 paracancer (normal), tumor and peripheral blood samples were collected from 23 patients with CRC from The Cancer Genome Atlas database (https://portal.gdc.cancer.gov/). After the immune cells were sorted by multicolor flow cytometry, the single cell transcriptome and B cell receptor group library were sequenced using the 10X Genomics platform, and the data were analyzed using bioinformatics tools such as Seurat. The differences in the number and function of B cell infiltration between tumor and normal tissue, the interaction between B cell subsets and T cells and myeloid cell subsets, and the transcription factor regulatory network of B cell subsets were explored and analyzed. Compared with normal tissue, the infiltrating number of CD20+B cell subsets in tumor tissue increased significantly. Among them, germinal center B cells (GCB) played the most prominent role, with positive clone expansion and heavy chain mutation level increasing, and the trend of differentiation into memory B cells increased. However, the number of plasma cells in the tumor microenvironment decreased significantly, and the plasma cells secreting IgA antibodies decreased most obviously. In addition, compared with the immune microenvironment of normal tissues, GCB cells in tumor tissues became more closely connected with other immune cells such as T cells, and communication molecules that positively regulate immune function were significantly enriched. The role of GCB in CRC tumor microenvironment is greatly enhanced, and its affinity to tumor antigen is enhanced by its significantly increased heavy chain mutation level. Meanwhile, GCB has enhanced its association with immune cells in the microenvironment, which plays a positive anti-tumor effect.