Molecular Signatures of Human Regulatory T Cells in Colorectal Cancer and Polyps

How the Tumor Micromilieu Modulates the Recruitment and Activation of Colorectal Cancer-Infiltrating Lymphocytes

The successful treatment of advanced colorectal cancer disease still represents an insufficiently solved clinical challenge, which is further complicated by the fact that the majority of malignant colon tumors show only relatively low immunogenicity and therefore have only limited responsiveness to immunotherapeutic approaches, such as, for instance, the use of checkpoint inhibitors. As it has been well established over the past two decades that the local tumor microenvironment and, in particular, the quantity, quality, and activation status of intratumoral immune cells critically influence the clinical prognosis of patients diagnosed with colorectal cancer and their individual benefits from immunotherapy, the enhancement of the intratumoral accumulation of cytolytic effector T lymphocytes and other cellular mediators of the antitumor immune response has emerged as a targeted objective. For the future identification and clinical validation of novel therapeutic target structures, it will thus be essential to further decipher the molecular mechanisms and cellular interactions in the intestinal tumor microenvironment, which are crucially involved in immune cell recruitment and activation. In this context, our review article aims at providing an overview of the key chemokines and cytokines whose presence in the tumor micromilieu relevantly modulates the numeric composition and antitumor capacity of tumor-infiltrating lymphocytes.

An analysis of sexual dimorphism in the tumor microenvironment of colorectal cancer

Women with colorectal cancer (CRC) have survival advantages over men, yet the underlying mechanisms are unclear. T cell infiltration within the CRC tumor microenvironment (TME) correlates strongly with survival. We hypothesized that women with CRC have increased T cell infiltration and differential gene expression in the TME compared to men. Tissue microarrays comprising primary tumor, tumor infiltrated lymph nodes, and uninvolved colon were created from CRC patients. Proportions of CD4 positive (CD4+) and CD8 positive (CD8+) T cells were identified using immunohistochemistry. TME immune- and cancer-related genetic expression from primary and metastatic CRC tumor were also evaluated via the NanoStringIO360 panel and The Cancer Genome Atlas Project database. CD4+ was higher in tumor samples from women compared to men (22.04% vs. 10.26%, p=0.002) and also in lymph node samples (39.54% vs. 8.56%, p=0.001). CD8+ was increased in uninvolved colon from women compared to men (59.40% vs. 43.61%, p=0.015), and in stage I/II tumors compared to III/IV in all patients (37.01% vs. 23.91%, p=0.009). Top CD8+ tertile patients survived longer compared to the bottom (43.9 months vs. 25.3 months, p=0.007). Differential gene expression was observed in pathways related to Treg function, T cell activity, and T cell exhaustion, amongst several others, in women compared to men. Thus, significant sexual dimorphism exists in the TME that could contribute to survival advantages observed in female patients with CRC.

Joint Analysis of Microbial and Immune Cell Abundance in Liver Cancer Tissue Using a Gene Expression Profile Deconvolution Algorithm Combined With Foreign Read Remapping

Recent transcriptomics and metagenomics studies showed that tissue-infiltrating immune cells and bacteria interact with cancer cells to shape oncogenesis. This interaction and its effects remain to be elucidated. However, it is technically difficult to co-quantify immune cells and bacteria in their respective microenvironments. To address this challenge, we herein report the development of a complete a bioinformatics pipeline, which accurately estimates the number of infiltrating immune cells using a novel Particle Swarming Optimized Support Vector Regression (PSO-SVR) algorithm, and the number of infiltrating bacterial using foreign read remapping and the GRAMMy algorithm. It also performs systematic differential abundance analyses between tumor-normal pairs. We applied the pipeline to a collection of paired liver cancer tumor and normal samples, and we identified bacteria and immune cell species that were significantly different between tissues in terms of health status. Our analysis showed that this dual model of microbial and immune cell abundance had a better differentiation (84%) between healthy and diseased tissue. Caldatribacterium sp., Acidaminococcaceae sp., Planctopirus sp., Desulfobulbaceae sp.,Nocardia farcinica as well as regulatory T cells (Tregs), resting mast cells, monocytes, M2 macrophases, neutrophils were identified as significantly different (Mann Whitney Test, FDR< 0.05). Our open-source software is freely available from GitHub at https://github.com/gutmicrobes/PSO-SVR.git.

Genomic, Microbial and Immunological Microenvironment of Colorectal Polyps

Simple Summary

Colorectal cancers (CRC) initiate from small cell clusters known as polyps. Colonoscopic surveillance and removal of polyps is an important strategy to prevent CRC progression. Recent advances in sequencing technologies have highlighted genetic mutations in polyps that potentially contribute to CRC development. However, CRC might be considered more than a genetic disease, as emerging evidence describes early changes to immune surveillance and gut microbiota in people with polyps. Here, we review the molecular landscape of colorectal polyps, considering their genomic, microbial and immunological features, and discuss the potential clinical utility of these data.

Abstract

Colorectal cancer (CRC) develops from pre-cancerous cellular lesions in the gut epithelium, known as polyps. Polyps themselves arise through the accumulation of mutations that disrupt the function of key tumour suppressor genes, activate proto-oncogenes and allow proliferation in an environment where immune control has been compromised. Consequently, colonoscopic surveillance and polypectomy are central pillars of cancer control strategies. Recent advances in genomic sequencing technologies have enhanced our knowledge of key driver mutations in polyp lesions that likely contribute to CRC. In accordance with the prognostic significance of Immunoscores for CRC survival, there is also a likely role for early immunological changes in polyps, including an increase in regulatory T cells and a decrease in mature dendritic cell numbers. Gut microbiotas are under increasing research interest for their potential contribution to CRC evolution, and changes in the gut microbiome have been reported from analyses of adenomas. Given that early changes to molecular components of bowel polyps may have a direct impact on cancer development and/or act as indicators of early disease, we review the molecular landscape of colorectal polyps, with an emphasis on immunological and microbial alterations occurring in the gut and propose the potential clinical utility of these data.

IL-33 Signaling Alters Regulatory T Cell Diversity in Support of Tumor Development

Regulatory T cells (T_regs) can impair anti-tumor immune responses and are associated with poor prognosis in multiple cancer types. T_regs in human tumors span diverse transcriptional states distinct from those of peripheral T_regs, but their contribution to tumor development remains unknown. Here, we use single-cell RNA sequencing (RNA-seq) to longitudinally profile dynamic shifts in the distribution of T_regs in a genetically engineered mouse model of lung adenocarcinoma. In this model, interferon-responsive T_regs are more prevalent early in tumor development, whereas a specialized effector phenotype characterized by enhanced expression of the interleukin-33 receptor ST2 is predominant in advanced disease. T_reg-specific deletion of ST2 alters the evolution of effector T_reg diversity, increases infiltration of CD8⁺ T cells into tumors, and decreases tumor burden. Our study shows that ST2 plays a critical role in T_reg-mediated immunosuppression in cancer, highlighting potential paths for therapeutic intervention.

Ovarian Cancer Cells Promote Glycolysis Metabolism and TLR8-Mediated Metabolic Control of Human CD4+ T Cells

An immunosuppressive microenvironment is a major obstacle for successful tumor immunotherapy. Elucidating the regulatory mechanisms of energy metabolism and functionality in CD4⁺ T cells will provide insights for the development of novel immunotherapies for ovarian cancer (OC). An Agilent microarray was used to detect differences in gene expression between peripheral CD4⁺ T cells from five OC patients and those from five healthy controls. Functional pathway analysis was performed for differentially expressed genes. Gene expression profiles revealed significant differences in expression levels of 5,175 genes in peripheral CD4⁺ T cells from five patients with OC. Functional analysis indicated that the most significantly enriched pathways were metabolic pathways. Furthermore, eight glycolysis-related genes all showed significantly increased expression in peripheral CD4⁺ T cells of OC patients. Moreover, we established a coculture system of human CD4⁺ T cells with the OC cell line SKOV3, and then treated them with toll-like receptor 8 (TLR8) ligand ssRNA 40. Coculturing with SKOV3 cells could increase the expression of the eight glycolysis-related genes, promote glucose uptake and glycolysis in CD4⁺ T cells, induce the differentiation of CD4⁺ CD25⁺ Foxp3⁺ T cells, and enhance the suppression of naïve CD4⁺ T cells. Additionally, activated TLR8 signaling could mediate the reprogramming of glycolysis metabolism and function in CD4⁺ T cells. Overall, our study indicates that the SKOV3 coculture environment could regulate the glycolysis metabolism and function of CD4⁺ T cells, and also that TLR8 mediated the metabolic control of glycolysis in CD4⁺ T cells cocultured with SKOV3 cells. This provides a new direction for immunotherapy investigations in OC.

Calculation of immune cell proportion from batch tumor gene expression profile based on support vector regression

In addition to tumor cells, a large number of immune cells are found in the tumor microenvironment (TME) of cancer patients. Tumor-infiltrating immune cells play an important role in tumor progression and patient outcome. We improved the relative proportion estimation algorithm of immune cells based on RNA-seq gene expression profiling and solved the multiple linear regression model by support vector regression ([Formula: see text]-SVR). These steps resulted in increased robustness of the algorithm and more accurate calculation of the relative proportion of different immune cells in cancer tissues. This method was applied to the analysis of infiltrating immune cells based on 41 pairs of colorectal cancer tissues and normal solid tissues. Specifically, we compared the relative fractions of six types of immune cells in colorectal cancer tissues to those found in normal solid tissue samples. We found that tumor tissues contained a higher proportion of CD8 T cells and neutrophils, while B cells and monocytes were relatively low. Our pipeline for calculating immune cell proportion using gene expression profile data can be freely accessed from GitHub at https://github.com/gutmicrobes/EICS.git.

Relevance of Regulatory T Cells during Colorectal Cancer Development

In recent years, there has been a significant increase in the study of own and foreign human factors favoring the development of different types of cancer, including genetic and environmental ones. However, the fact that the immune response plays a fundamental role in the development of immunity and susceptibility to colorectal cancer (CRC) is much stronger. Among the many cell populations of the immune system that participate in restricting or favoring CRC development, regulatory T cells (Treg) play a major role in orchestrating immunomodulation during CRC. In this review, we established concrete evidence supporting the fact that Treg cells have an important role in the promotion of tumor development during CRC, mediating an increasing suppressive capacity which controls the effector immune response, and generating protection for tumors. Furthermore, Treg cells go through a process called "phenotypic plasticity", where they co-express transcription factors that promote an inflammatory profile. We reunited evidence that describes the interaction between the different effector populations of the immune response and its modulation by Treg cells adapted to the tumor microenvironment, including the mechanisms used by Treg cells to suppress the protective immune response, as well as the different subpopulations of Treg cells participating in tumor progression, generating susceptibility during CRC development. Finally, we discussed whether Treg cells might or might not be a therapeutic target for an effective reduction in the morbidity and mortality caused by CRC.

Colorectal Cancer in Inflammatory Bowel Disease

Patients with inflammatory bowel disease (IBD) are at an increased risk for developing colorectal cancer (CRC). However, the incidence has declined over the past 30 years, which is probably attributed to raise awareness, successful CRC surveillance programs and improved control of mucosal inflammation through chemoprevention. The risk factors for IBD-related CRC include more severe disease (as reflected by the extent of disease and the duration of poorly controlled disease), family history of CRC, pseudo polyps, primary sclerosing cholangitis, and male sex. The molecular pathogenesis of inflammatory epithelium might play a critical role in the development of CRC. IBD-related CRC is characterized by fewer rectal tumors, more synchronous and poorly differentiated tumors compared with sporadic cancers. There is no significant difference in sex distribution, stage at presentation, or survival. Surveillance is vital for the detection and subsequently management of dysplasia. Most guidelines recommend initiation of surveillance colonoscopy at 8 to 10 years after IBD diagnosis, followed by subsequent surveillance of 1 to 2 yearly intervals. Traditionally, surveillance colonoscopies with random colonic biopsies were used. However, recent data suggest that high definition and chromoendoscopy are better methods of surveillance by improving sensitivity to previously "invisible" flat dysplastic lesions. Management of dysplasia, timing of surveillance, chemoprevention, and the surgical approaches are all areas that stimulate various discussions. The aim of this review is to provide an up-to-date focus on CRC in IBD, from laboratory to bedside.

Transcriptional Signature Derived from Murine Tumor-Associated Macrophages Correlates with Poor Outcome in Breast Cancer Patients

Tumor-associated macrophages (TAMs) are frequently the most abundant immune cells in cancers and are associated with poor survival. Here, we generated TAM molecular signatures from K14cre;Cdh1flox/flox;Trp53flox/flox (KEP) and MMTV-NeuT (NeuT) transgenic mice that resemble human invasive lobular carcinoma (ILC) and HER2+ tumors, respectively. Determination of TAM-specific signatures requires comparison with healthy mammary tissue macrophages to avoid overestimation of gene expression differences. TAMs from the two models feature a distinct transcriptomic profile, suggesting that the cancer subtype dictates their phenotype. The KEP-derived signature reliably correlates with poor overall survival in ILC but not in triple-negative breast cancer patients, indicating that translation of murine TAM signatures to patients is cancer subtype dependent. Collectively, we show that a transgenic mouse tumor model can yield a TAM signature relevant for human breast cancer outcome prognosis and provide a generalizable strategy for determining and applying immune cell signatures provided the murine model reflects the human disease.

Dendrobium officinale polysaccharides alleviate colon tumorigenesis via restoring intestinal barrier function and enhancing anti-tumor immune response

Intact epithelial barrier and mucosal immune system are crucial for maintaining intestinal homeostasis. Previous study indicated that Dendrobium officinale polysaccharides (DOPS) can regulate immune responses and inflammation to alleviate experimental colitis. However, it remains largely unknown whether DOPS can suppress AOM/DSS-induced colorectal cancer (CRC) model through its direct impact on intestinal barrier function and intestinal mucosal immunity. Here, we demonstrated the therapeutic action of DOPS for CRC model and further illustrated its underlying mechanisms. Treatment with 5-aminosalicylic acid (5-ASA) and DOPS significantly improved the clinical signs and symptoms of chronic colitis, relieve colon damage, suppress the formation and growth of colon tumor in CRC mice. Moreover, administration of DOPS effectively preserved the intestinal barrier function via reducing the loss of zonula occludens-1 (ZO-1) and occludin in adjacent tissues and carcinomatous tissues. Further studies demonstrated that DOPS improved the metabolic ability of tumor infiltrated CD8⁺ cytotoxic T lymphocytes (CTLs) and reduced the expression of PD-1 on CTLs to enhance the anti-tumor immune response in the tumor microenvironments (TME). Together, the conclusions indicated that DOPS restore intestinal barrier function and enhance intestinal anti-tumor immune response to suppress CRC, which may be a novel strategy for the prevention and treatment of CRC.

Hyperresponsiveness to interferon gamma exposure as a response mechanism to anti-PD-1 therapy in microsatellite instability colorectal cancer

Colorectal cancer (CRC) with high-level microsatellite instability (MSI-H) tends to be associated with a better response to programmed death receptor-1 (PD-1) blockade than does microsatellite stable CRC. However, emerging evidence makes the use of programmed death ligand-1 (PD-L1) as a biomarker problematic. Here, we sought to characterize the interactions between PD-L1 expression and the response to PD-1 blockade therapy in BALB/c mice with a subcutaneous tumor challenge. We further focused on interferon gamma (IFNγ)-induced PD-L1 expression in an in vitro setting to evaluate the responsiveness to IFNγ exposure and the specific signaling of PD-1 in HCT116 and SW480 cell lines. In this study, enhanced PD-L1 expression increased survival in CT26 cells, and PD-1 blockade increased the CTL profile and apoptotic cells in mice with CRC. Our in vitro findings showed that PD-L1 expression was significantly upregulated by a low-dose IFNγ treatment, and the MSI-H cell line might exhibit hyperresponsiveness to IFNγ exposure partly through the JAK-STAT pathway. These results suggest that intrinsic PD-L1 in cooperation with extrinsic IFNγ exposure in CRC may be more responsive to anti-PD-1 therapy, mainly through the CTL profile in the tumor microenvironment.

GARP Dampens Cancer Immunity by Sustaining Function and Accumulation of Regulatory T Cells in the Colon

Activated regulatory T (Treg) cells express the surface receptor glycoprotein-A repetitions predominant (GARP), which binds and activates latent TGFβ. How GARP modulates Treg function in inflammation and cancer remains unclear. Here we demonstrate that loss of GARP in Treg cells leads to spontaneous inflammation with highly activated CD4⁺ and CD8⁺ T cells and development of enteritis. Treg cells lacking GARP were unable to suppress pathogenic T-cell responses in multiple models of inflammation, including T-cell transfer colitis. GARP^-/- Treg cells were significantly reduced in the gut and exhibited a reduction in CD103 expression, a colon-specific migratory marker. In the colitis-associated colon cancer model, GARP on Treg cells dampened immune surveillance, and mice with GARP^-/- Treg cells exhibited improved antitumor immunity. Thus, GARP empowers the functionality of Treg cells and their tissue-specific accumulation, highlighting the importance of cell surface TGFβ in Treg function and GARP as a potential therapeutic target for colorectal cancer therapy.Significance: These findings uncover functions of membrane-bound TGFβ and GARP that tune the activity of Treg cells, highlighting a potential treatment strategy in autoimmune diseases and cancer.

Targeting cytokines secreted by CD4+ CD25high CD127low regulatory T cells inhibits ovarian cancer progression

Epithelial ovarian cancer (EOC) is one of the major malignant cancers with high rates of early metastasis in which regulatory T cells (Tregs) play an important role. Tregs suppress immune responses and promote the development of tumours in patients with EOC. However, the underlying mechanisms remain unclear. In this study, we found higher levels of CD4⁺ CD25^high CD127^low Tregs in patients with EOC than in patients with benign ovarian tumours and healthy donors. The immune inhibitory effect of Tregs functions by maintaining high levels of immunosuppressive cytokines in EOC. The high levels of Tregs and related cytokines (TGF-β1 or IL-10) were associated with lymphatic metastasis and FIGO stages of patients with EOC. Expression of matrix metalloproteinase (MMP)-2 and tissue inhibitors of metalloproteinase (TIMP)-2 in EOC cell lines were significantly regulated in the coculture experiment with CD4⁺ CD25^high CD127^low Tregs sorted from EOC patients. Levels of MMP-2 and TIMP-2 conversely changed after blocking IL-10R and TGF-β1R in EOC cells. The invasion ability of EOC cells was also significantly downregulated in this process. The metastasis of EOC cells was correlated with the levels of TGF-β1 or IL-10. These findings suggested that immunosuppressive cytokines secreted by CD4⁺ Tregs could be a novel target for inhibiting EOC progression.

Regulatory T-cell heterogeneity and the cancer immune response

The frequency of circulating or tumour-infiltrating regulatory T cells (Tregs) has been associated with poor patient survival in many cancers including breast, melanoma and lung. It has been hypothesised that Tregs impact the anti-tumour function of effector T cells, resulting in worse outcomes for patients. However, high infiltrates of Tregs have been associated with a positive outcome of patients in a minority of cancers including colorectal, bladder and oesophageal. In addition, many studies have shown no impact of Tregs in patient outcome. Traditionally, research has identified Tregs as forkhead box P3 (FOXP3+) T cells in order to make such associations. Recently, it has become evident that regulatory populations are very heterogeneous, and this heterogeneity is essential for Treg function. Treg heterogeneity likely affects predictions of patient outcome, and different Treg populations may have different influences on tumours. The study of Tregs in cancer must include a better definition of the cells analysed. This review will focus primarily on colorectal cancer in humans, due to mixed data on the impact of Tregs on patient outcome in this disease.