Accumulation of CCR4⁺CTLA-4 FOXP3⁺CD25(hi) regulatory T cells in colon adenocarcinomas correlate to reduced activation of conventional T cells

Unraveling Th subsets: insights into their role in immune checkpoint inhibitor therapy

T helper (Th) cell subsets play pivotal roles in regulating immune responses within the tumor microenvironment, influencing both tumor progression and anti-tumor immunity. Among these subsets, Th1 cells promote cytotoxic responses through the production of IFN-γ, while Th2 cells and regulatory T cells (Tregs) exert immunosuppressive effects that support tumor growth. Th9 and Th17 cells have context-dependent roles, contributing to both pro-inflammatory and regulatory processes in tumor immunity. Tumor antigen-specific T cells within the tumor microenvironment often exhibit a dysfunctional phenotype due to increased expression of inhibitory receptors such as CTLA-4 and PD-1, leading to reduced antitumor activity. Monoclonal antibodies that block these inhibitory signals-collectively known as immune checkpoint inhibitors (ICIs)-can reactivate these T cells, enhancing their ability to target and destroy cancer cells. Recent advancements have highlighted the critical role of T helper subsets in modulating responses to ICIs, with their interactions remaining a focus of ongoing research. Both positive and negative effects of ICIs have been reported in relation to Th cell subsets, with some effects depending on the type of tumor microenvironment. This review summarizes the crucial roles of different T helper cell subsets in tumor immunity and their complex relationship with immune checkpoint inhibitor therapy.

Identification of the Binding Epitope of an Anti-mouse CCR4 Monoclonal Antibody, C4Mab-1

C-C chemokine receptor 4 (CCR4) is one of G protein-coupled receptors, and interacts with chemokines, CCL17 and CCL22. CCR4 is expressed on T cells such as helper T type 2 cells, regulatory T cells, and interleukin 17-producing T helper cells. CCR4 is associated with T cells trafficking into the tumor microenvironment, and is associated with tumor progression or metastasis. Therefore, CCR4 may be a potential therapeutic option for T cell malignancies. C₄Mab-1 is a novel anti-mouse CCR4 (mCCR4) monoclonal antibody produced by mCCR4 N-terminal peptide immunization. C₄Mab-1 is useful for flow cytometric analysis. In this study, we conducted the epitope mapping of C₄Mab-1 using enzyme-linked immunosorbent assay (ELISA) and peptide blocking assay. The result of ELISA indicated that Thr7, Asp8, and Gln11 of mCCR4 are the critical amino acids for the C₄Mab-1 binding. Furthermore, peptide blocking assay by flow cytometry showed that Thr7, Asp8, and Gln11 of mCCR4 are essential for C₄Mab-1 binding to mCCR4-overexpressed Chinese hamster ovary-K1 (CHO/mCCR4) cells, and Val6, Thr9, and Thr10 are involved in the C₄Mab-1 binding to CHO/mCCR4 cells. These results indicate that the critical binding epitope of C₄Mab-1 includes Thr7, Asp8, and Gln11 of mCCR4.

The Role of Tumor Microenvironment and Immune Response in Colorectal Cancer Development and Prognosis

Colorectal cancer (CRC) is one of the most common cancers worldwide. The patient’s prognosis largely depends on the tumor stage at diagnosis. The pathological TNM Classification of Malignant Tumors (pTNM) staging of surgically resected cancers represents the main prognostic factor and guidance for decision-making in CRC patients. However, this approach alone is insufficient as a prognostic predictor because clinical outcomes in patients at the same histological tumor stage can still differ. Recently, significant progress in the treatment of CRC has been made due to improvements in both chemotherapy and surgical management. Immunotherapy-based approaches are one of the most rapidly developing areas of tumor therapy. This review summarizes the current knowledge about the tumor microenvironment (TME), immune response and its interactions with CRC development, immunotherapy and prognosis.

Emerging role for thymic stromal lymphopoietin-responsive regulatory T cells in colorectal cancer progression in humans and mice

Recruitment of regulatory T cells (T_regs) to tumors is a hallmark of cancer progression. Tumor-derived factors, such as the cytokine thymic stromal lymphopoietin (TSLP), can influence T_reg function in tumors. In our study, we identified a subset of T_regs expressing the receptor for TSLP (TSLPR⁺ T_regs) that were increased in colorectal tumors in humans and mice and largely absent in adjacent normal colon. This T_reg subset was also found in the peripheral blood of patients with colon cancer but not in the peripheral blood of healthy control subjects. Mechanistically, we found that this T_reg subset coexpressed the interleukin-33 (IL-33) receptor [suppressor of tumorigenicity 2 (ST2)] and had high programmed cell death 1 (PD-1) and cytotoxic lymphocyte-associated antigen 4 (CTLA-4) expression, regulated in part by the transcription factor Mef2c. T_reg-specific deletion of TSLPR, but not ST2, was associated with a reduction in tumor number and size with concomitant increase in T_H1 cells in tumors in chemically induced mouse models of colorectal cancer. Therapeutic blockade of TSLP using TSLP-specific monoclonal antibodies effectively inhibited the progression of colorectal tumors in this mouse model. Collectively, these data suggest that TSLP controls the progression of colorectal cancer through regulation of tumor-specific T_reg function and represents a potential therapeutic target that requires further investigation.

Mogamulizumab in Combination with Nivolumab in a Phase I/II Study of Patients with Locally Advanced or Metastatic Solid Tumors

PURPOSE

The aim of the study was to determine safety, antitumor activity, and pharmacodynamic profile of mogamulizumab, an anti-CCR4 monoclonal antibody targeting effector regulatory T cells (Treg) in combination with the checkpoint inhibitor nivolumab in patients with locally advanced or metastatic solid tumors.

PATIENTS AND METHODS

This was a multicenter, dose-finding (phase I), and dose expansion (phase II) study (NCT02705105) in patients with locally advanced or metastatic solid tumors. There were no dose-limiting toxicities in phase I with mogamulizumab 1 mg/kg every week for cycle 1 followed by 1 mg/kg every 2 weeks plus nivolumab 240 mg every 2 weeks intravenously, and cohort expansion occurred at this dose level.

RESULTS

All 114 patients treated with mogamulizumab 1 mg/kg plus nivolumab 240 mg in phases I (n = 4) and II (n = 110) were assessed for safety and efficacy. Mogamulizumab plus nivolumab showed acceptable safety and tolerability. Objective response rate was 10.5% [95% confidence interval (CI), 5.6-17.7; 3 complete and 9 partial responses]. Disease control rate was 36.8%. Median duration of response was 14.4 months. Median progression-free survival was 2.6 (95% CI, 2.3-3.1) months, and median overall survival was 9.5 (95% CI, 5.9-13.5) months.

CONCLUSIONS

Combination of mogamulizumab with nivolumab for treatment of patients with locally advanced or metastatic solid tumors did not result in enhanced efficacy. Tolerability of mogamulizumab 1 mg/kg plus nivolumab 240 mg was acceptable.

Inflammatory Bowel Disease-Associated Colorectal Cancer: Translational Risks from Mechanisms to Medicines

The cumulative impact of chronic inflammation in patients with inflammatory bowel diseases predisposes to the development of inflammatory bowel disease-associated colorectal cancer [IBD-CRC]. Inflammation can induce mutagenesis, and the relapsing-remitting nature of this inflammation, together with epithelial regeneration, may exert selective pressure accelerating carcinogenesis. The molecular pathogenesis of IBD-CRC, termed the 'inflammation-dysplasia-carcinoma' sequence, is well described. However, the immunopathogenesis of IBD-CRC is less well understood. The impact of novel immunosuppressive therapies, which aim to achieve deep remission, is mostly unknown. Therefore, this timely review summarizes the clinical context of IBD-CRC, outlines the molecular and immunological basis of disease pathogenesis, and considers the impact of novel biological therapies.

CAR Treg: A new approach in the treatment of autoimmune diseases

Regulatory T cells (Tregs) have the role of regulating self-tolerance, and suppressing immune responses. Defects in Treg function and number can lead to in loss of tolerance or autoimmune disease. To treat or control autoimmune diseases, one of the options is to develop immune tolerance for Tregs cell therapy, which includes promotion and activation. Recently, cell-based treatment as a promising approach to increase cells function and number has been developed. Cell therapy by chimeric T antigen receptor (CAR-T) cells has shown significant efficacy in the treatment of leukemia, which has led researchers to use CAR-T cells in other diseases like autoimmune diseases. Here, we describe the existing treatments for autoimmune diseases and the available treatments based on Treg, their benefits and restrictions for implementation in clinical trials. We also discussed potential solutions to overcome these limitations. It seems novel designs of CARs to be new hope for autoimmune diseases and expected to be a potential cure option in a wide array of disease in the future. Therefore, it is very important to address this issue and increase information about it.

Intratumoral regulatory T cells from colon cancer patients comprise several activated effector populations

Background

Intratumoral regulatory T cells (Treg) in colon cancer are a heterogeneous cell population, with potential impact on patient outcome. Generally, a high Treg infiltration has been correlated to a worse patient outcome, but it is still unclear how the composition of different Treg subsets affects patient relapse and survival. In this study, we used mass and flow cytometry to characterize Treg in colon tumors and corresponding unaffected tissue, followed by a correlation to clinical parameters and patient outcome.

Results

Using mass cytometry, we defined 13 clusters of intestinal Treg, three of which were enriched in the tumors. The two most enriched clusters were defined by their expression of the proliferation marker Ki67 and CD56, respectively. The Treg accumulating in the tumors expressed inducible T-cell co-stimulator (ICOS), OX-40, and CD39, indicating that they were effector Treg (eTreg). Intratumoral CD39⁺ Treg also had a higher expression of Foxp3, suggesting a higher suppressive activity, and we subsequently used CD39 as a marker for eTreg. Our further studies showed that colon tumors can be divided into two tumor groups, based on the proportion of CD39⁺ putative eTreg in the tumors. This property was independent of both tumor microsatellite status and tumor stage, which are important factors in predicting cancer disease progression. In a prospective study of forty-four colon cancer patients, we also showed that patients with a high CD39 expression on tumor-infiltrating Treg have a tendency towards a less favorable patient outcome in terms of cumulative cancer-specific survival.

Conclusions

This study uncovers novel subsets of tumor-infiltrating Treg in colon cancer, and suggests that CD39 may be a potential therapeutic target in patients with microsatellite stable colon tumors, which are usually refractory to checkpoint blockade therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00449-1.

Regulatory T cells reduce endothelial neutral sphingomyelinase 2 to prevent T-cell migration into tumors

Endothelial cells are key regulators of transendothelial migration and their secretion of chemokines and expression of adhesion molecules facilitates lymphocyte entry into tissues. Previously, we demonstrated that Tregs can reduce transendothelial migration of T cells into tumors by decreasing endothelial CXCL10 secretion, but the mechanism by which this occurs is still not known. In this study, we aimed to define how Tregs decrease transendothelial migration into tumors. mRNA sequencing of intestinal tumor endothelial cells from Treg depleted mice identified neutral sphingomyelinase 2 (nSMase2) as a gene downregulated in the presence of Tregs. nSMase2 is expressed in human umbilical vein endothelial cells (HUVECs) and was decreased after coculture with Tregs. Furthermore, blocking of nSMase2 activity in vitro decreased VCAM1, CX3CL1, and CXCL10 expression in HUVECs, mirroring the same decrease found in Treg cocultures. In the APC^min/+ mouse model of intestinal cancer, nSMase2 is lower in tumor endothelial cells than in unaffected small intestine and chronic treatment with a nSMase2 inhibitor suppressed the increased migration that is otherwise seen in the absence of Tregs. We conclude that nSMase2 is an important mediator in endothelial cells supporting transendothelial migration, which may be targeted by Tregs to reduce T-cell migration into tumors.

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.

Recruitment and Expansion of Tregs Cells in the Tumor Environment-How to Target Them?

Simple Summary

The immune response against cancer is generated by effector T cells, among them cytotoxic CD8⁺ T cells that destroy cancer cells and helper CD4⁺ T cells that mediate and support the immune response. This antitumor function of T cells is tightly regulated by a particular subset of CD4⁺ T cells, named regulatory T cells (Tregs), through different mechanisms. Even if the complete inhibition of Tregs would be extremely harmful due to their tolerogenic role in impeding autoimmune diseases in the periphery, the targeted blockade of their accumulation at tumor sites or their targeted depletion represent a major therapeutic challenge. This review focuses on the mechanisms favoring Treg recruitment, expansion and stabilization in the tumor microenvironment and the therapeutic strategies developed to block these mechanisms.

Abstract

Regulatory T cells (Tregs) are present in a large majority of solid tumors and are mainly associated with a poor prognosis, as their major function is to inhibit the antitumor immune response contributing to immunosuppression. In this review, we will investigate the mechanisms involved in the recruitment, amplification and stability of Tregs in the tumor microenvironment (TME). We will also review the strategies currently developed to inhibit Tregs’ deleterious impact in the TME by either inhibiting their recruitment, blocking their expansion, favoring their plastic transformation into other CD4⁺ T-cell subsets, blocking their suppressive function or depleting them specifically in the TME to avoid severe deleterious effects associated with Treg neutralization/depletion in the periphery and normal tissues.

Immune Microenvironment: New Insight for Familial Adenomatous Polyposis

Currently, the main treatment for familial adenomatous polyposis (FAP) is surgery, however, surgery is far from ideal as there are many complications such as uncontrollable bowel movements, pouch inflammation, anastomotic stricture, and secondary fibroids. Therefore, it is necessary to further expand the understanding of FAP and develop new treatments for FAP. The immune microenvironment including immune cells and cytokines, plays an important role in FAP and the progression of FAP to adenocarcinoma, thus it may be a promising treatment for FAP. In the current review, we summarized the recent progress in the immune microenvironment of FAP.

Mogamulizumab in Combination with Durvalumab or Tremelimumab in Patients with Advanced Solid Tumors: A Phase I Study

PURPOSE

The study goal was to determine safety, antitumor activity, and pharmacodynamic profile of mogamulizumab, an anti-C-C chemokine receptor 4 (anti-CCR4) mAb targeting effector regulatory T cells (eTreg), in combination with mAb checkpoint inhibitors durvalumab or tremelimumab.

PATIENTS AND METHODS

This was a multicenter, phase I, dose escalation study, followed by disease-specific cohort expansion (NCT02301130). Mogamulizumab dose escalation proceeded with concurrent dose escalation of durvalumab or tremelimumab in patients with advanced solid tumors. Cohort expansion occurred with mogamulizumab 1 mg/kg plus durvalumab 10 mg/kg or tremelimumab 10 mg/kg in patients with advanced pancreatic cancer.

RESULTS

Forty patients were enrolled during dose escalation, followed by 24 patients during dose expansion. No dose-limiting toxicities occurred during dose escalation. No new or unexpected toxicities were seen. Tolerability, the primary endpoint, was acceptable utilizing mogamulizumab 1 mg/kg plus durvalumab or tremelimumab 10 mg/kg in the combined dose escalation and dose expansion cohorts (each n = 19). At these doses, the objective response rate was 5.3% (95% confidence interval, 0.1%-26.0%; one partial response) with each combination treatment. At all doses, mogamulizumab treatment led to almost complete depletion of peripheral eTregs, as well as reduction of intratumoral Tregs in the majority of patients. There was no clear correlation of clinical response with peripheral or intratumoral reduction in CCR4⁺ eTregs or with baseline degree of CCR4⁺ expression.

CONCLUSIONS

Mogamulizumab in combination with durvalumab or tremelimumab did not result in potent antitumor efficacy in patients with advanced solid tumors. Tolerability of mogamulizumab 1 mg/kg combined with durvalumab or tremelimumab 10 mg/kg was acceptable.

A high-throughput chemotaxis detection method for CCR4+ T cell migration inhibition using image cytometry

Chemotaxis is an important aspect of immune cell behavior within the tumor microenvironment (TME). One prominent example of chemotaxis within the TME is the migration of regulatory T cells (Tregs) in response to the chemokine ligands CCL17 and CCL22. Tregs within the TME cause the suppression of anti-tumor immunity and inhibition of the effect of immunotherapeutic treatments. Therefore, the ability to screen for therapeutic antibodies that can inhibit or stimulate the chemotaxis of various immune cell types is crucial. Traditionally, chemotaxis is studied by determining the number of cells in the bottom reservoir of a Transwell microplate using flow cytometry; however, this method is time-consuming and thus not appropriate for high-throughput screening purposes. The Celigo Image Cytometer has been employed to perform high-throughput cell-based assays and was used to develop a new detection method for chemotaxis measurement. The image-based detection method was developed using chemokine ligands CCL17 and CCL22 to induce the migration of CCR4⁺ T cells and directly count them on the bottom of the Transwell plates. Finally, the method was applied to measure the inhibitory effects of commercially available anti-CCL17 and anti-CCL22 antibodies, which caused a dose-dependent decrease in the number of migrated T cells. The proposed image cytometry method allowed screening of multiple antibodies at various concentrations, simultaneously, which can improve the efficiency for discovering potential antibody candidates that can induce or inhibit recruitment of immune cells to the tumor microenvironment.

Cancer Immunotherapies Targeting Tumor-Associated Regulatory T Cells

Tumor-associated regulatory T cells (Tregs) are important effectors in the tumor microenvironment (TME), acting as accomplices in the promotion of tumor progression. Currently, the importance of removing the immunosuppressive activity in the TME has received its due attention, and Tregs have been focused on. The cytokine-receptor axes are among the essential signaling pathways in immunocytes, and tumor-associated Tregs are no exception. Therefore, manipulating cytokine-receptor pathways may be a promising effective strategy for treating various malignancies. Here, we summarize the classification, immunosuppressive mechanisms, existing immunotherapies, and potential biomarkers related to tumor-infiltrating Tregs to guide the development of effective cancer immunotherapies.

Function and dysfunction of plasma cells in intestine

As the main player in humoral immunity, antibodies play indispensable roles in the body's immune system. Plasma cells (PCs), as antibody factories, are important contributors to humoral immunity. PCs, recognized by their unique marker CD138, are always discovered in the medullary cords of spleen and lymph nodes and in bone marrow and mucosal lymphoid tissue. This article will review the origin and differentiation of PCs, characteristics of short- and long-lived PCs, and the secretion of antibodies, such as IgA, IgM, and IgG. PCs play a crucial role in the maintenance of intestinal homeostasis using immunomodulation though complex mechanisms. Clearly, PCs play functional roles in maintaining intestinal health, but more details are needed to fully understand all the other effects of intestinal PCs.

Regulatory T cells control endothelial chemokine production and migration of T cells into intestinal tumors of APCmin/+ mice

Tumor-infiltrating lymphocytes are crucial for anti-tumor immunity. We have previously shown that regulatory T cells (Treg) are able to reduce T-cell transendothelial migration in vitro and accumulation of effector T cells in intestinal tumors in vivo. Treg depletion also resulted in increased levels of the chemokines CXCL9 and CXCL10 specifically in the tumors. In this study, we investigated the mechanisms for Treg mediated suppression of T-cell migration into intestinal tumors in the APCmin/+ mouse model. By breeding APCmin/+ mice with DEREG mice, which harbour a high affinity diphtheria toxin receptor under the control of the FOXP3 promoter, we were able to deplete Treg in tumor-bearing mice. Using adoptive transfer experiments, we could document a markedly increased migration of T cells specifically into Treg depleted tumors, and that Treg depletion results in increased production of the CXCR3 ligand CXCL10 from endothelial cells in the tumors. Furthermore, we were able to demonstrate that T cells use CXCR3 to migrate into intestinal tumors. In addition, human colon adenocarcinomas express high levels of mRNA CXCR3 ligands and tumor endothelial cells produce CXCL9 and CXCL10 ex vivo. In conclusion, this study demonstrates that Treg reduce endothelial CXCL10 production, inhibit T-cell migration into tumors and that CXCR3 mediated signalling is crucial for lymphocyte accumulation in intestinal tumors. Thus, immunotherapy aimed at Treg depletion may be effective by increasing not only T effector cell activity, but also their accumulation in tumors.

Checkpoints and beyond - Immunotherapy in colorectal cancer

Immunotherapy is the latest revolution in cancer therapy. It continues to show impressive results in malignancies like melanoma and others. At least so far, effects are modest in colorectal cancer (CRC) and only a subset of patients benefits from already approved checkpoint inhibitors. In this review, we discuss major hurdles of immunotherapy like the immunosuppressive niche and low immunogenicity of CRC next to current achievements of checkpoint inhibitors, interleukin treatment and adoptive cell transfer (dendritic cells/cytokine induced killer cells, tumor infiltrating lymphocytes, chimeric antigen receptor cells, T cell receptor transfer) in pre-clinical models and clinical trials. We intensively examine approaches to overcome low immunogenicity by combination of different therapies and address future strategies of therapy as well as the need of predictive factors in this emerging field of precision medicine.

Targeting Regulatory T Cells to Treat Patients With Systemic Lupus Erythematosus

Regulatory T cells (Tregs) are central in integration and maintenance of immune homeostasis. Since breakdown of self-tolerance is a major culprit in the pathogenesis of systemic lupus erythematosus (SLE), restoration of the immune tolerance through the manipulation of Tregs can be exploited to treat patients with SLE. New information has revealed that Tregs besides their role in suppressing the immune response are important in tissue protection and regeneration. Expansion of Tregs with low-dose IL-2 represents an approach to control the autoimmune response. Moreover, control of Treg metabolism can be exploited to restore or improve their function. Here, we summarize the function and diversity of Tregs and recent strategies to improve their function in patients with SLE.

Colorectal cancer-infiltrating T lymphocytes display a distinct chemokine receptor expression profile

Background

T lymphocytes exert important homeostatic functions in the healthy intestinal mucosa, whereas in case of colorectal cancer (CRC), infiltration of T lymphocytes into the tumor is crucial for an effective anti-tumor immune response. In both situations, the recruitment mechanisms of T lymphocytes into the tissues are essential for the immunological functions deciding the outcome. The recruitment of T lymphocytes is largely dependent on their expression of various chemokine receptors. The aim of this study was to identify potential chemokine receptors involved in the recruitment of T lymphocytes to normal human colonic mucosa and to CRC tissue, respectively, by examining the expression of 16 different chemokine receptors on T lymphocytes isolated from these tissues.

Methods

Tissues were collected from patients undergoing bowel resection for CRC. Lymphocytes were isolated through enzymatic tissue degradation of CRC tissue and nearby located unaffected mucosa, respectively. The expression of a broad panel of chemokine receptors on the freshly isolated T lymphocytes was examined by flow cytometry.

Results

In the normal colonic mucosa, the frequencies of cells expressing CCR2, CCR4, CXCR3, and CXCR6 differed significantly between CD4⁺ and CD8⁺ T lymphocytes, suggesting that the molecular mechanisms mediating T lymphocyte recruitment to the gut differ between CD4⁺ and CD8⁺ T lymphocytes. In CRC, the frequencies of cells expressing CCR2 and CXCR5 were significantly lower in both the CD4⁺ and CD8⁺ T lymphocyte populations compared to unaffected colonic mucosa, and the frequency of CCR9⁺ cytotoxic T lymphocytes was significantly decreased in CRC tissue.

Conclusions

With regard to the normal gut mucosa, the results suggest that the molecular mechanisms mediating T lymphocyte recruitment differ between CD4⁺ and CD8⁺ T lymphocytes, which are important for understanding gut homeostasis. Importantly, T lymphocytes from CRC compared to normal colonic tissue displayed a distinct chemokine receptor expression profile, suggesting that mechanisms for recruitment of T lymphocytes to CRC tissue are skewed compared to normal colonic mucosa. Understanding these mechanisms could help in developing new strategies in cancer immunotherapy and to optimize already available alternatives such as immune checkpoint inhibitors.

Leukocyte trafficking in tumor microenvironment

The tumor microenvironment consists of both malignant and non-malignant cells and a plethora of soluble mediators. Different types of tumors have specific tumor microenvironments characterized by distinct chemokines and chemotactic factors that influence leukocyte recruitment. The immune cell infiltrate continuously interacts with stroma cells and influence tumor growth. Emerging evidence suggests that the regulation of the composition and the metabolic state of tumor-associated leukocytes may represent a new promising intervention strategy. Here we summarize the current knowledge on the role of tumor-associated immune cells in tumor growth and dissemination, with a specific focus on the nature of the chemotactic factors responsible for their accumulation and activation in tumors.

The Complexity of alpha E beta 7 Blockade in Inflammatory Bowel Diseases

Monoclonal antibodies targeting integrins are emerging as new treatment option in inflammatory bowel diseases. Integrins are molecules involved in cell adhesion and signalling. After the successful introduction of anti-α4β7, currently anti-β7 is under evaluation in a phase three trial. Anti-β7 blocks both α4β7/MAdCAM-1 and αEβ7/E-cadherin interaction, targeting both the homing to and the retention in the gut of potential pathological T cells. Since the physiological and potential pathological roles of immune cells expressing αEβ7 are less distinct than of those expressing α4β7, an overview of the current state of knowledge on αEβ7 in mice and humans in both health and inflammatory bowel diseases is presented here, also addressing the potential consequences of anti-β7 treatment.

Regulatory T Cells: Molecular and Cellular Basis for Immunoregulation

CD4⁺ regulatory T cells (Tregs) are a highly immune-suppressive subset of CD4⁺ T cells, characterized by expression of the master regulatory transcription factor FOXP3. Tregs are proven to play central roles in the maintenance of self-tolerance in healthy individuals. Tregs are involved in maintaining immune homeostasis: they protect hosts from developing autoimmune diseases and allergy, whereas in malignancies, they promote tumor progression by suppressing anti-tumor immunity. Elucidating factors influencing Treg homeostasis and function have important implications for understanding disease pathogenesis and identifying therapeutic opportunities. Thus, the manipulating Tregs for up- or down-regulation of their suppressive function is a new therapeutic strategy for treating various diseases including autoimmune disorders and cancer. This review will focus on recent advances in how Tregs integrate extracellular and intracellular signals to control their survival and stability. Deeper mechanistic understanding of disease-specific Treg development, maintenance, and function could make disease-specific Treg-targeted therapy more effective, resulting in an increase of efficacy and decrease of side effects related to manipulating Tregs.

Ccl22 Diverts T Regulatory Cells and Controls the Growth of Melanoma

T regulatory cells (Treg) avert autoimmunity, but their increased levels in melanoma confer a poor prognosis. To explore the basis for Treg accumulation in melanoma, we evaluated chemokine expression in patients. A 5-fold increase was documented in the Treg chemoattractants CCL22 and CCL1 in melanoma-affected skin versus unaffected skin, as accompanied by infiltrating FoxP3⁺ T cells. In parallel, there was an approximately two-fold enhancement in expression of CCR4 in circulating Treg but not T effector cells. We hypothesized that redirecting Treg away from tumors might suppress autoimmune side effects caused by immune checkpoint therapeutics now used widely in the clinic. In assessing this hypothesis, we observed a marked increase in skin Treg in mice vaccinated with Ccl22, with repetitive vaccination sufficient to limit Treg accumulation and melanoma growth in the lungs of animals challenged by tumor cell injection, whether using a prevention or treatment protocol design. The observed change in Treg accumulation in this setting could not be explained by Treg conversion. Overall, our findings offered a preclinical proof of concept for the potential use of CCL22 delivered by local injection as a strategy to enhance the efficacious response to immune checkpoint therapy while suppressing its autoimmune side effects. Cancer Res; 76(21); 6230-40. ©2016 AACR.

Roles of regulatory T cells in cancer immunity

CD4(+) regulatory T cells (Tregs) expressing the transcription factor FoxP3 are highly immune suppressive and play central roles in the maintenance of self-tolerance and immune homeostasis, yet in malignant tumors they promote tumor progression by suppressing effective antitumor immunity. Indeed, higher infiltration by Tregs is observed in tumor tissues, and their depletion augments antitumor immune responses in animal models. Additionally, increased numbers of Tregs and, in particular, decreased ratios of CD8(+) T cells to Tregs among tumor-infiltrating lymphocytes are correlated with poor prognosis in various types of human cancers. The recent success of cancer immunotherapy represented by immune checkpoint blockade has provided a new insight in cancer treatment, yet more than half of the treated patients did not experience clinical benefits. Identifying biomarkers that predict clinical responses and developing novel immunotherapies are therefore urgently required. Cancer patients whose tumors contain a large number of neoantigens stemming from gene mutations, which have not been previously recognized by the immune system, provoke strong antitumor T-cell responses associated with clinical responses following immune checkpoint blockade, depending on the resistance to Treg-mediated suppression. Thus, integration of a strategy restricting Treg-mediated immune suppression may expand the therapeutic spectrum of cancer immunotherapy towards patients with a lower number of neoantigens. In this review, we address the current understanding of Treg-mediated immune suppressive mechanisms in cancer, the involvement of Tregs in cancer immunotherapy, and strategies for effective and tolerable Treg-targeted therapy.

FOXP3 and CEACAM6 expression and T cell infiltration in the occurrence and development of colon cancer

The transcription factor forkhead box P3 (FOXP3) is involved in immune cell regulation, and carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is an adhesion molecule of the immunoglobulin superfamily. These two genes are associated with cancer progression. In the current study, colon tissue specimens from 78 cases of colon cancer (including 40 of stage I-II and 38 of stage III-IV), 30 cases of colonic adenoma and 12 healthy controls were collected from the First Affiliated Hospital of Soochow University between January 2010 and December 2011. The expression of cluster of differentiation (CD) 3, CD4, CD8, CD45RO, CEACAM6 and FOXP3 in colon tissues was examined by immunohistochemical analysis. In addition, a reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay, based on SYBR Green I, was used to detect CD3, CD4, CD8, CD45RO, CEACAM6 and FOXP3 mRNA levels in the paraffin block specimens. CD3⁺, CD8⁺ and CD45RO⁺ T cell infiltrations in colonic adenoma were significantly higher than in normal colonic mucosa (P<0.001, P=0.001 and P<0.001, respectively). However, CD3⁺, CD8⁺ and CD45RO⁺ lymphocytes in stage III-IV colon cancer tissues were lower than in normal control tissues (P=0.015, P=0.002 and P=0.041, respectively); consistently, CD3⁺, CD4⁺, CD8⁺ and CD45RO⁺ lymphocytes in stage III-IV tissues were even more markedly lower compared with adenoma (P=0.001, P<0.001, P<0.001 and P<0.001, respectively). Similarly, CD3⁺, CD8⁺ and CD45RO⁺ T cell infiltration was lower in stage I-II cancer tissues compared with adenoma (P=0.001, P<0.001 and P<0.001). CD3⁺, CD4⁺, CD8⁺ and CD45RO⁺ T cell infiltrations were also significantly higher in stage I-II compared with stage III-IV cancer tissues (P<0.001, P=0.045, P<0.001 and P<0.001, respectively). CEACAM6 was found to gradually increase from normal colon tissue to adenoma and cancer tissue. FOXP3 was expressed more highly in stage I-II compared with normal tissues (P=0.014), and was even higher in stage III-IV (P<0.001). These results were verified using RT-qPCR, which yielded almost identical results. In summary, the current study demonstrates that FOXP3, CEACAM6 and T cell infiltration are significantly associated with the occurrence and progression of colon cancer, and that immune reactions vary between different stages of colon cancer development.

Kinome Profiling of Regulatory T Cells: A Closer Look into a Complex Intracellular Network

Regulatory T cells (Treg) are essential for T cell homeostasis and maintenance of peripheral tolerance. They prevent activation of auto-reactive T effector cells (Teff) in the context of autoimmunity and allergy. Otherwise, Treg also inhibit effective immune responses against tumors. Besides a number of Treg-associated molecules such as Foxp3, CTLA-4 or GARP, known to play critical roles in Treg differentiation, activation and function, the involvement of additional regulatory elements is suggested. Herein, kinase activities seem to play an important role in Treg fine tuning. Nevertheless, our knowledge regarding the complex intracellular signaling pathways controlling phenotype and function of Treg is still limited and based on single kinase cascades so far. To gain a more comprehensive insight into the pathways determining Treg function we performed kinome profiling using a phosphorylation-based kinome array in human Treg at different activation stages compared to Teff. Here we have determined intriguing quantitative differences in both populations. Resting and activated Treg showed an altered pattern of CD28-dependent kinases as well as of those involved in cell cycle progression. Additionally, significant up-regulation of distinct kinases such as EGFR or CK2 in activated Treg but not in Teff not only resemble data we obtained in previous studies in the murine system but also suggest that those specific molecular activation patterns can be used for definition of the activation and functional state of human Treg. Taken together, detailed investigation of kinome profiles opens the possibility to identify novel molecular mechanisms for a better understanding of Treg biology but also for development of effective immunotherapies against unwanted T cell responses in allergy, autoimmunity and cancer.

Immune Checkpoint Modulation in Colorectal Cancer: What's New and What to Expect

Colorectal cancer (CRC), as one of the most prevalent types of cancer worldwide, is still a leading cause of cancer related mortality. There is an urgent need for more efficient therapies in metastatic disease. Immunotherapy, a rapidly expanding field of oncology, is designed to boost the body's natural defenses to fight cancer. Of the many approaches currently under study to improve antitumor immune responses, immune checkpoint inhibition has thus far been proven to be the most effective. This review will outline the treatments that take advantage of our growing understanding of the role of the immune system in cancer, with a particular emphasis on immune checkpoint molecules, involved in CRC pathogenesis.

Human Mucosa-Associated Invariant T Cells Accumulate in Colon Adenocarcinomas but Produce Reduced Amounts of IFN-γ

Mucosa-associated invariant T (MAIT) cells are innate-like T cells with a conserved TCR α-chain recognizing bacterial metabolites presented on the invariant MHC-related 1 molecule. MAIT cells are present in intestinal tissues and liver, and they rapidly secrete IFN-γ and IL-17 in response to bacterial insult. In colon cancer, IL-17-driven inflammation promotes tumor progression, whereas IFN-γ production is essential for antitumor immunity. Thus, tumor-associated MAIT cells may affect antitumor immune responses by their secreted cytokines. However, the knowledge of MAIT cell presence and function in tumors is virtually absent. In this study, we determined the frequency, phenotype, and functional capacity of MAIT cells in colon adenocarcinomas and unaffected colon lamina propria. Flow cytometric analyses showed significant accumulation of MAIT cells in tumor tissue, irrespective of tumor stage or localization. Colonic MAIT cells displayed an activated memory phenotype and expression of chemokine receptors CCR6 and CCR9. Most MAIT cells in unaffected colon tissues produced IFN-γ, whereas only few produced IL-17. Colonic MAIT cells also produced TNF-α, IL-2, and granzyme B. In the tumors, significantly lower frequencies of IFN-γ-producing MAIT cells were seen, whereas there were no differences in the other cytokines analyzed, and in vitro studies showed that secreted factors from tumor tissue reduced IFN-γ production from MAIT cells. In conclusion, MAIT cells infiltrate colon tumors but their ability to produce IFN-γ is substantially reduced. We suggest that MAIT cells have the capacity to promote local immune responses to tumors, but factors in the tumor microenvironment act to reduce MAIT cell IFN-γ production.

High intratumoral FOXP3⁺ T regulatory cell (Tregs) density is an independent good prognosticator in nodal negative colorectal cancer

Immunologic profiling of colorectal cancer (CRC) may help to predict the tumors metastatic potential and patients with an aggressive tumor, although not yet metastasized at time of surgery might benefit from adjuvant therapy. In this study we evaluated the prognostic significance of FOXP3(+) T regulatory cells (Tregs), CD3(+) and CD8(+) lymphocyte densities and conventional histopathologic features in nodal negative (n = 820, UICC stage II) CRC. Immunohistochemical studies showed that high expression of FOXP3(+) Tregs is significantly linked to a better clinical outcome (P = 0.0001). In multivariate analysis including tumor stage, tumor grade, type of tumor invasion margin (pushing vs. infiltrating type), lymphovascular invasion (absent vs. present), CD3(+), CD8(+) and FOXP3(+) Tregs expression, only low tumor stage, absence of lymphovascular invasion and high Foxp3 Tregs density showed prognostic significance (P = 0.0132, P = 0.0022 AND P = 0.0234, respectively). Our findings argue towards a clinical utility of FOXP3(+) Tregs immunostaining as an independent good prognostic biomarker in stage II colorectal cancers. FOXP3(+) Tregs immunoscoring, assessment of tumor stage and lymphovascular invasion may help to define stage II cancers with a potentially aggressive behavior and CRC patients who might benefit from adjuvant therapy. A two-scale immunosore related to the median count of FOXP3(+) Tregs proved to be easy and quick to perform.

Treg-cell depletion promotes chemokine production and accumulation of CXCR3(+) conventional T cells in intestinal tumors

Colorectal cancer (CRC) is one of the most prevalent tumor types worldwide and tumor-infiltrating T cells are crucial for anti-tumor immunity. We previously demonstrated that Treg cells from CRC patients inhibit transendothelial migration of conventional T cells. However, it remains unclear if local Treg cells affect lymphocyte migration into colonic tumors. By breeding APC(Min/+) mice with depletion of regulatory T cells mice, expressing the diphtheria toxin receptor under the control of the FoxP3 promoter, we were able to selectively deplete Treg cells in tumor-bearing mice, and investigate the impact of these cells on the infiltration of conventional T cells into intestinal tumors. Short-term Treg-cell depletion led to a substantial increase in the frequencies of T cells in the tumors, attributed by both increased infiltration and proliferation of T cells in the Treg-cell-depleted tumors. We also demonstrate a selective increase of the chemokines CXCL9 and CXCL10 in Treg-cell-depleted tumors, which were accompanied by accumulation of CXCR3(+) T cells, and increased IFN-γ mRNA expression. In conclusion, Treg-cell depletion increases the accumulation of conventional T cells in intestinal tumors, and targeting Treg cells could be a possible anti-tumor immunotherapy, which not only affects T-cell effector functions, but also their recruitment to tumors.

Skewed T-helper (Th)1/2- and Th17/T regulatory‑cell balances in patients with renal cell carcinoma

The characterization of CD4⁺ T-cell subsets reflects the immune status and is important in the maintenance of tumorigenesis and homeostasis. To identify changes in the balance of T helper (Th)1, Th2, Th17 and regulatory T cells (Treg) in individuals with renal cell carcinoma (RCC), the present study investigated a total of 131 patients with RCC and 36 healthy volunteers. The number of CD4⁺ T-bet⁺ cells, CD4⁺ GATA binding protein 3⁺ cells, CD4⁺ RAR-related orphan receptor γt⁺ cells, CD4⁺ CD25^hi CD127^lo CD45RA⁻ cells and CD4⁺ CD25^hi CD127^lo CD45RA⁺ cells, defined as Th1, Th2, Th17, activated and naïve Treg cells, respectively, were detected in the peripheral blood using flow cytometric analysis. In addition, tumor-infiltrating forkhead box P3 (Foxp3)⁺ cells were examined using immunohistochemistry. Compared with healthy volunteers, a significant decrease in the peripheral percentages of Th1, activated and naïve Treg cells was observed in patients with RCC, while those of the Th2 and Th17 cells were increased. In particular, as the tumor stage and grade progressed, the levels of Th1, activated and naïve Treg cells in the peripheral blood decreased; however, the levels of Th2 and Th17 cells increased. Furthermore, the number of tumor-infiltrating Foxp3⁺ cells increased with increasing tumor stage. These results demonstrated that the balance of Th1 and Th2 cells was skewed towards the Th2 profile and the balance of Th17 and Treg cells was skewed towards the Th17 profile in the peripheral blood of patients with renal cell carcinoma (RCC) and Treg cells were recruited to the tumor sites. Therefore, dysfunctional host anti-tumor immunity was observed in patients with RCC, with a skewed Th1/Th2 and Th17/Treg balance.

Altered chemokine production and accumulation of regulatory T cells in intestinal adenomas of APC(Min/+) mice

Tumor progression in the colon moves from aberrant crypt foci to adenomatous polyps to invasive carcinomas. The composition of the tumor-infiltrating leukocyte population affects the ability of the immune system to fight the tumor. T cell infiltration into colorectal adenocarcinomas, particularly T helper 1 (Th1) type T cells as well as increased regulatory T cell (Treg) frequencies, is correlated with improved prognosis. However, whether Th1 cells and Tregs are already present at the adenoma stage is not known. In this study, the APC(Min/+) mouse model of intestinal adenomatous polyposis was used to investigate tumor-associated lymphocyte subsets and the mechanisms of their accumulation into gastrointestinal adenomas. Compared to unaffected tissue, adenomas accumulated CD4(+)FoxP3(+) putative Treg in parallel with lower frequencies of conventional T cells and B cells. The accumulation of Treg was also observed in human adenomatous polyps. Despite high Treg numbers, the function of conventional T cells present in the APC(Min/+) adenomas was not different from those in the unaffected tissue. Adenomas displayed an altered chemokine balance, with higher CCL17 and lower CXCL11 and CCL25 expression than in the unaffected tissue. In parallel, CXCR3(+) Tregs were largely absent from adenomas. The data indicate that already in early stages of tumor development, the balance of lymphocyte-recruiting chemokines is altered possibly contributing to the observed shift toward higher frequencies of Treg.

Epstein-Barr virus infection induces an increase of T regulatory type 1 cells in Hodgkin lymphoma patients

Epstein-Barr Virus (EBV) is present in the neoplastic cells of around 20-30% of patients with Hodgkin Lymphoma (HL). Although, an immunosuppressive environment is currently described in HL patients, little is known concerning the regulatory mechanism induced by EBV proteins expression in tumour cells. This study aimed to investigate an association between regulatory Type 1 cells (Tr1) and EBV tissue positivity in HL patients. Transcriptomic analysis of both EBV-positive and EBV-negative tumours showed that EBV infection increased gene expression of Tr1-related markers (ITGA2, ITGB2, LAG3) and associated-immunosuppressive cytokines (IL10). This up-regulation was associated with an over-expression of several chemokine markers known to attract T-helper type 2 (Th2) and regulatory T cells thus contributing to immune suppression. This Tr1 cells recruitment in EBV-positive HL was confirmed by immunohistochemical analysis of frozen nodes biopsies and by flow cytometric analysis of peripheral blood mononuclear cells of EBV-positive patients. Additionally, we showed that IL10 production was significantly enhanced in tumours and blood of EBV-positive HL patients. Our results propose a new model in which EBV can recruit Tr1 cells to the nodes' microenvironment, suggesting that the expression of EBV proteins in tumour cells could enable the escape of EBV-infected tumour cells from the virus-specific CTL response.

The intratumoural subsite and relation of CD8(+) and FOXP3(+) T lymphocytes in colorectal cancer provide important prognostic clues

Background:

To find improved tools for prognostic evaluation in patients with colorectal cancer (CRC), we have analysed how infiltration of cytotoxic T lymphocytes (CD8⁺) and regulatory T lymphocytes (FoxP3⁺) correlates to prognosis, not only according to quantity and relation, but also to subsite within tumours of different molecular characteristics (microsatellite instability and CpG island methylator phenotype status).

Methods:

CD8 and FOXP3 expression was evaluated by immunohistochemistry in 426 archival tumour tissue samples from patients surgically resected for CRC. The average infiltration of CD8⁺ and FOXP3⁺ cells was assessed along the tumour invasive front, in the tumour centre and within the tumour epithelium (intraepithelial).

Results:

We found that infiltration of CD8⁺ T lymphocytes within the tumour epithelium provided the strongest prognostic information (P<0.001). At the tumour invasive front and tumour centre, FOXP3 expression withheld the strongest association to prognosis (P<0.001), suggesting FOXP3⁺ T-lymphocyte infiltration to be a better prognostic tool than CD8⁺ T lymphocytes at these intratumoural subsites. We further analysed the possible prognostic impact of the relation between these T-cell subsets, finding that a high intraepithelial CD8 expression was associated with a better patient outcome, independent of FOXP3 infiltration. In groups of low intraepithelial CD8 expression, however, a high infiltration rate of FOXP3⁺ cells at the tumour invasive front, significantly improved prognosis.

Conclusions:

Analyses of intraepithelial infiltration of CD8⁺ T lymphocytes, infiltration of FOXP3⁺ T lymphocytes at the tumour front or centre, and the relation between these subsets, may be a valuable tool for predicting prognosis in colon cancer.

Highly prevalent colorectal cancer-infiltrating LAP⁺ Foxp3⁻ T cells exhibit more potent immunosuppressive activity than Foxp3⁺ regulatory T cells

Although elevated CD4⁺Foxp3⁺ regulatory T cell (Treg) frequencies within tumors are well documented, the functional and phenotypic characteristics of CD4⁺Foxp3⁺ and CD4⁺Foxp3⁻ T cell subsets from matched blood, healthy colon, and colorectal cancer require in-depth investigation. Flow cytometry revealed that the majority of intratumoral CD4⁺Foxp3⁺ T cells (Tregs) were Helios⁺ and expressed higher levels of cytotoxic T-lymphocyte antigen 4 (CTLA-4) and CD39 than Tregs from colon and blood. Moreover, ∼30% of intratumoral CD4⁺Foxp3⁻ T cells expressed markers associated with regulatory functions, including latency-associated peptide (LAP), lymphocyte activation gene-3 (LAG-3), and CD25. This unique population of cells produced interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), and was ∼50-fold more suppressive than Foxp3⁺ Tregs. Thus, intratumoral Tregs are diverse, posing multiple obstacles to immunotherapeutic intervention in colorectal malignancies.

Expression of the chemokine decoy receptor D6 is decreased in colon adenocarcinomas

Recruitment of immune cells to tumors is a complex process crucial for both inflammation-driven tumor progression and specific anti-tumor cytotoxicity. Chemokines control the directed migration of immune cells, and their actions are partly controlled by nonsignaling chemokine decoy receptors. The role of the receptors such as D6, Duffy antigen receptor for chemokines and ChemoCentryx chemokine receptor in immunity to tumors is still unclear. Using real-time PCR, we detected significantly decreased expression of D6 mRNA in colon tumors compared to unaffected mucosa. D6 protein was expressed by lymphatic endothelium and mononuclear cells in the colon lamina propria and detected by immunohistochemistry in two out of six tissue samples containing high D6 mRNA levels, whereas no staining was observed in any tissue samples expressing low mRNA levels. When examining the density of lymphatic vessels in colon tumors, we detected a marked increase in vessels identified by the lymphatic endothelial marker Lyve-1, excluding passive regulation of D6 due to decreased lymphatic vessel density. In parallel, the Treg-recruiting chemokine CCL22, which is sequestered by D6, was threefold increased in tumor tissue. Furthermore, we could show that low D6 expression correlated to more invasive tumors and that tumor location influences D6 expression, which is lower in the more distal parts of the colon. The data support that regulation of D6 by colon tumors results in altered levels of proinflammatory CC chemokines, thereby shaping the local chemokine network to favor tumor survival. This may have implications for the design of future immunotherapy for colon cancer.

Progressive Increase of Regulatory T Cells and Decrease of CD8+ T Cells and CD8+ T Cells/Regulatory T Cells Ratio during Colorectal Cancer Development

Background

We examined the distribution of CD8+ T cells and regulatory T cells (Tregs), measured the CD8+ T cell/Tregs ratio, investigated the relationship between Tregs and cyclooxygenase-2 (COX-2) expression during colorectal cancer (CRC) development.

Methods

We performed immunohistochemical staining for CD8, forkhead box P3, E-cadherin, and COX-2 in 32 cases of invasive CRC, 10 cases of intramucosal CRC, 27 cases of high-grade tubular adenoma, 22 cases of low-grade tubular adenoma, and 32 cases of non-neoplastic conditions.

Results

We observed a progressive increase in Tregs, and a decrease in CD8+ T cells and the CD8+ T cells/Tregs ratio during CRC development. The alterations were most severe in high-grade tubular adenoma and CRC. COX-2 expression was positively associated with Tregs infiltration. The degree of T cell infiltration differed among tumor compartment and the ratio in the tumor center was the lowest of all areas. The ratio and number of CD8+ T cells in the tumor center and the invasive front of invasive CRC were associated with gender, differentiation, node metastasis and tumor budding.

Conclusions

Alteration in the distribution of both CD8+T cells and Tregs may contribute to the generation of an immune environment suitable for the development and progression of CRC.

Expression of CTLA-4 and Foxp3 in peripheral blood T cells of patients with squamous cell laryngeal carcinoma

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4, CD152) and Foxp3 (forkhead box P3) are receptors present on T cells which play a critical role in the down-regulation of antigen-activated immune responses. To evaluate the potential influences of CTLA-4 and Foxp3 on cancer invasiveness, a case-control study was conducted in 86 patients treated for squamous cell laryngeal carcinoma. The abundance of CTLA-4 and Foxp3 gene transcripts in the purified peripheral blood mononuclear cells (PBMCs) by quantitative real-time PCR (qRT-PCR) was determined. The analysis of proteins by Western blot was performed. The relationships between CTLA-4 and Foxp3 gene and protein expression as well as the aggressiveness of tumor determined on pT, type and depth of invasion were investigated. Our work revealed a significant dependence of mRNA CTLA-4 on tumor front grading (TFG) total score (p = 0.04) as well as CTLA-4 protein expression on pT (p = = 0.03) and type of invasion (p = 0.03). Advanced pT3-pT4 tumors with diffuse infiltration and > 14 TFG points were characterized by higher average values of CTLA-4 protein in PBMCs. Our data also demonstrated significant differences between Foxp3 protein levels in relation to pT (p = 0.04), depth of invasion (p = = 0.02) and type of invasion (p = 0.03). In tumors with the highest invasiveness identified by the pT3-pT4 status, deep invasion with involvement of cartilage and diffuse infiltration, the highest Foxp3 protein level was observed. In conclusion, these results suggest an impact of CTLA-4 and Foxp3 in determining proliferative and aggressive potential of laryngeal carcinoma, highlighting the significance of CTLA-4 and Foxp3 as potential predictive indicators.

CCR7 expression and intratumoral FOXP3+ regulatory T cells are correlated with overall survival and lymph node metastasis in gastric cancer

The aim of this study was to investigate the prognostic value of chemokine receptor CCR7 expression and intratumoral FOXP3⁺ regulatory T cells (Tregs) in gastric cancer. CCR7⁺ tumor cells and FOXP3⁺ Tregs were assessed by immunohistochemistry in tissue microarrays containing gastric cancer from 133 patients. Prognostic effects of low or high CCR7 and FOXP3 expression were evaluated by Cox regression and Kaplan-Meier analysis, as well as the correlation between CCR7 positive score and intratumoral FOXP3⁺ cell number in a longitudinal assessment. The analysis showed that the high expression levels of CCR7 and FOXP3 were detected in 69.9% and 65.4% of cases, respectively. High CCR7 expression in gastric cancer cells was significantly associated with poor overall survival (OS) (P = 0.010) and lymph node metastasis (P = 0.009), and was an independent factor for worse OS (P = 0.023) by multivariate analysis. High numbers of intratumoral FOXP3⁺ Tregs significantly correlated with shorter OS (P = 0.021) and lymph node metastasis (P = 0.024), and was also an independent factor for adverse OS (P = 0.035). Furthermore, there was a significantly positive correlation between CCR7 positive score and intratumoral FOXP3⁺ cell number (r = 0.949, P<0.001). These results revealed that CCR7 expression in gastric cancer cells and intratumoral FOXP3⁺ Tregs could be considered as a co-indicator of clinical prognosis of gastric cancer.

Natural and induced T regulatory cells in cancer

CD4+Foxp3+ T regulatory (Treg) cells control many facets of immune responses ranging from autoimmune diseases, to inflammatory conditions, and cancer in an attempt to maintain immune homeostasis. Natural Treg (nTreg) cells develop in the thymus and constitute a critical arm of active mechanisms of peripheral tolerance particularly to self antigens. A growing body of knowledge now supports the existence of induced Treg (iTreg) cells which may derive from a population of conventional CD4+ T cells. The fork-head transcription factor (Foxp3) typically is expressed by natural CD4+ Treg cells, and thus serves as a marker to definitively identify these cells. On the contrary, there is less consensus on what constitutes iTreg cells as their precise definition has been somewhat elusive. This is in part due to their distinct phenotypes which are shaped by exposure to certain inflammatory or "assault" signals stemming from the underlying immune disorder. The "policing" activity of Treg cells tends to be uni-directional in several pathological conditions. On one end of the spectrum, Treg cell suppressive activity is beneficial by curtailing T cell response against self-antigens and allergens thus preventing autoimmune diseases and allergies. On the other end however, their inhibitory roles in limiting immune response against pseudo-self antigens as in tumors often culminates into negative outcomes. In this review, we focus on this latter aspect of Treg cell immunobiology by highlighting the involvement of nTreg cells in various animal models and human tumors. We further discuss iTreg cells, relationship with their natural counterpart, and potential co-operation between the two in modulating immune response against tumors. Lastly, we discuss studies focusing on these cells as targets for improving anti-tumor immunity.

Natural and induced T regulatory cells in cancer

CD4+Foxp3+ T regulatory (Treg) cells control many facets of immune responses ranging from autoimmune diseases, to inflammatory conditions, and cancer in an attempt to maintain immune homeostasis. Natural Treg (nTreg) cells develop in the thymus and constitute a critical arm of active mechanisms of peripheral tolerance particularly to self antigens. A growing body of knowledge now supports the existence of induced Treg (iTreg) cells which may derive from a population of conventional CD4+ T cells. The fork-head transcription factor (Foxp3) typically is expressed by natural CD4+ Treg cells, and thus serves as a marker to definitively identify these cells. On the contrary, there is less consensus on what constitutes iTreg cells as their precise definition has been somewhat elusive. This is in part due to their distinct phenotypes which are shaped by exposure to certain inflammatory or “assault” signals stemming from the underlying immune disorder. The “policing” activity of Treg cells tends to be uni-directional in several pathological conditions. On one end of the spectrum, Treg cell suppressive activity is beneficial by curtailing T cell response against self-antigens and allergens thus preventing autoimmune diseases and allergies. On the other end however, their inhibitory roles in limiting immune response against pseudo-self antigens as in tumors often culminates into negative outcomes. In this review, we focus on this latter aspect of Treg cell immunobiology by highlighting the involvement of nTreg cells in various animal models and human tumors. We further discuss iTreg cells, relationship with their natural counterpart, and potential co-operation between the two in modulating immune response against tumors. Lastly, we discuss studies focusing on these cells as targets for improving anti-tumor immunity.

Impaired migration of IgA-secreting cells to colon adenocarcinomas

Local inflammation is a strong risk factor for the development of gastrointestinal adenocarcinomas. Mucosal regulatory T cells and IgA-secreting cells both contribute to reduce inflammatory responses, and their recruitment to tissues is dependent on local production of chemokines. More specifically, IgA-secreting cells are recruited to mucosal tissues by CCL28 signalling through CCR10. Here, we examined the recruitment of IgA-secreting plasma cells to tumor-associated mucosa in patients suffering from colon adenocarcinoma. Flow cytometric analyses of single cell suspensions from tumor-associated and unaffected colon mucosa showed a marked decrease in CD19(+)CD38(high)IgA(+) plasmablasts in the tumor-associated mucosa, while the total frequencies of B and T cells were similar. This finding was confirmed in ELISPOT assays, demonstrating a 64 % reduction in the frequencies of IgA-secreting cells among cells from the tumor-associated mucosa. The few IgA(+) plasmablasts present in the tumor did not express CCR10, and functional migration assays demonstrated that IgA-secreting cells from tumor-associated mucosa did not migrate in response to CCL28. Taken together, our results show an impaired migration of IgA-secreting cells to colon tumors, presumably caused by a decreased production of CCL28 in the tumor. The lack of local IgA antibodies may lead to impaired barrier function and increased bacterial colonization, driving further inflammatory responses and promoting tumor growth.

Inflammatory and regulatory T cells contribute to a unique immune microenvironment in tumor tissue of colorectal cancer patients

Colorectal cancer is one of the five leading causes of cancer mortality worldwide. The mechanisms of pathogen clearance, inflammation and regulation by T cells in the healthy bowel are also important in controlling tumor growth. The majority of studies analyzing T cells and their relationship to colorectal tumor growth have focused on individual T cell markers or gene clusters and thus the complexity of the T cell response contributing to the growth of the tumor is not clear. We have studied the T cells in colorectal cancer patients and have defined a unique T cell signature for colorectal tumor tissue. Using a novel analytical flow cytometric approach in concert with confocal microscopy, we have shown that the tumor has a lower frequency of effector T cells (CD69+), but a higher frequency of both regulatory (CD25hi Foxp3+) and inflammatory T cells (IL-17+) compared with associated nontransformed bowel tissue. We have also identified minor populations of T cells expressing conventional markers of both inflammatory and regulatory T cells (CD4+IL-17+Foxp3+) in the tumor tissue. These cells may represent intermediate populations or they may dictate an inflammatory versus regulatory function in surrounding T cells. Together, these data describe an immune microenvironment in colorectal cancer unique to the tumor tissue and distinct from the surrounding healthy bowel tissue, and this distinct environment is reflected by a gradient of T cells expressing markers of multiple T cell populations. These findings may be used to improve diagnosis and prognosis of colorectal cancer patients.