Colorectal cancer-derived Foxp3(+) IL-17(+) T cells suppress tumour-specific CD8+ T cells

Tissue adaptation of CD4 T lymphocytes in homeostasis and cancer

The immune system is traditionally classified as a defense system that can discriminate between self and non-self or dangerous and non-dangerous situations, unleashing a tolerogenic reaction or immune response. These activities are mainly coordinated by the interaction between innate and adaptive cells that act together to eliminate harmful stimuli and keep tissue healthy. However, healthy tissue is not always the end point of an immune response. Much evidence has been accumulated over the years, showing that the immune system has complex, diversified, and integrated functions that converge to maintaining tissue homeostasis, even in the absence of aggression, interacting with the tissue cells and allowing the functional maintenance of that tissue. One of the main cells known for their function in helping the immune response through the production of cytokines is CD4+ T lymphocytes. The cytokines produced by the different subtypes act not only on immune cells but also on tissue cells. Considering that tissues have specific mediators in their architecture, it is plausible that the presence and frequency of CD4+ T lymphocytes of specific subtypes (Th1, Th2, Th17, and others) maintain tissue homeostasis. In situations where homeostasis is disrupted, such as infections, allergies, inflammatory processes, and cancer, local CD4+ T lymphocytes respond to this disruption and, as in the healthy tissue, towards the equilibrium of tissue dynamics. CD4+ T lymphocytes can be manipulated by tumor cells to promote tumor development and metastasis, making them a prognostic factor in various types of cancer. Therefore, understanding the function of tissue-specific CD4+ T lymphocytes is essential in developing new strategies for treating tissue-specific diseases, as occurs in cancer. In this context, this article reviews the evidence for this hypothesis regarding the phenotypes and functions of CD4+ T lymphocytes and compares their contribution to maintaining tissue homeostasis in different organs in a steady state and during tumor progression.

Unremitting pro-inflammatory T-cell phenotypes, and macrophage activity, following paediatric burn injury

Objectives

The aim of this study was to characterise the dynamic immune profile of paediatric burn patients for up to 18 months post-burn.

Methods

Flow cytometry was used to measure 25 cell markers, chemokines and cytokines which reflected both pro-inflammatory and anti-inflammatory immune profiles. Peripheral blood mononuclear cells from 6 paediatric burn patients who had returned for repeated burn and scar treatments for > 4 timepoints within 12 months post-burn were compared to four age-matched healthy controls.

Results

While overall proportions of T cells, NK cells and macrophages remained relatively constant, over time percentages of these immune cells differentiated into effector and proinflammatory cell phenotypes including Th17 and activated γδ T cells. Circulating proportions of γδ T cells increased their expression of pro-inflammatory mediators throughout the burn recovery, with a 3-6 fold increase of IL-17 at 1-3 weeks, and NFκβ 9-18 months post-burn. T-regulatory cell plasticity was also observed, and Treg phenotype proportions changed from systemically reduced skin-homing T-regs (CCR4+) and increased inflammatory (CCR6+) at 1-month post-burn, to double-positive cell types (CCR4+CCR6+) elevated in circulation for 18 months post-burn. Furthermore, Tregs were observed to proportionally express less IL-10 but increased TNF-α over 18 months.

Conclusion

Overall, these results indicate the circulating percentages of immune cells do not increase or decrease over time post-burn, instead they become highly specialised, inflammatory and skin-homing. In this patient population, these changes persisted for at least 18 months post-burn, this 'immune distraction' may limit the ability of immune cells to prioritise other threats post-burn, such as respiratory infections.

High ANO1 expression is a prognostic factor and correlated with an immunosuppressive tumor microenvironment in pancreatic cancer

Background

Aminooctylamine (ANO1) plays an oncogenic role in various cancers. However. its role in pancreatic cancer (PC) has rarely been studied. This study investigated the prognostic value of ANO1 and its correlation with the tumor microenvironment (TME) in PC.

Methods

Consecutive patients with PC (n = 119) were enrolled. The expression of ANO1 in cancer cells, the expression of fibroblast activation protein (FAP) and alpha smooth muscle actin in cancer-associated fibroblasts (CAFs), and the numbers of CD8- and FOXP3-positive tumor-infiltrating lymphocytes (TILs) were evaluated using immunohistochemistry. The prognostic value of ANO1 and its correlation with CAF subgroups and TILs were analyzed. The possible mechanism of ANO1 in the TME of PC was predicted using the the Cancer Genome Atlas (TCGA) dataset.

Results

The expression of AN01 was correlated with overall survival (OS) and disease-free survival. Multi-factor analysis showed that high ANO1 expression was an independent adverse prognostic factor for OS (hazard ratio, 4.137; P = 0.001). ANO1 expression was positively correlated with the expression of FAP in CAFs (P < 0.001) and negatively correlated with the number of CD8-positive TILs (P = 0.005), which was also validated by bioinformatics analysis in the TCGA dataset. Moreover, bioinformatic analysis of the TCGA dataset revealed that ANO1 may induce an immunosuppressive tumor microenvironment in pancreatic cancer in a paracrine manner.

Conclusion

ANO1 is a prognostic factor in patients with PC after radical resection. ANO1 may induce an immunosuppressive tumor microenvironment in PC in a paracrine manner, suggesting that ANO1 may be a novel therapeutic target.

Effects of Helicobacter pylori infection on intestinal microbiota, immunity and colorectal cancer risk

Infecting about half of the world´s population, Helicobacter pylori is one of the most prevalent bacterial infections worldwide and the strongest known risk factor for gastric cancer. Although H. pylori colonizes exclusively the gastric epithelium, the infection has also been associated with various extragastric diseases, including colorectal cancer (CRC). Epidemiological studies reported an almost two-fold increased risk for infected individuals to develop CRC, but only recently, direct causal and functional links between the chronic infection and CRC have been revealed. Besides modulating the host intestinal immune response, H. pylori is thought to increase CRC risk by inducing gut microbiota alterations. It is known that H. pylori infection not only impacts the gastric microbiota at the site of infection but also leads to changes in bacterial colonization in the distal large intestine. Considering that the gut microbiome plays a driving role in CRC, H. pylori infection emerges as a key factor responsible for promoting changes in microbiome signatures that could contribute to tumor development. Within this review, we want to focus on the interplay between H. pylori infection, changes in the intestinal microbiota, and intestinal immunity. In addition, the effects of H. pylori antibiotic eradication therapy will be discussed.

Expression characteristics of peripheral lymphocyte programmed death 1 and FoxP3+ Tregs in gastric cancer during surgery and chemotherapy

BACKGROUND

Programmed death 1 (PD-1) and CD4+CD25+FoxP3+ expression in peripheral blood T-cells has been previously reported in various types of cancer. However, the specific variation tendency during surgery and chemotherapy, as well as their relationship in gastric cancer patients, still remain unclear. Understanding this aspect may provide some novel insights for future studies on tumor recurrence and tumor immune escape, and also serve as a reference for determining the optimal timing and dose of clinical anti-PD-1 antibodies.

AIM

To observe and analyze the expression characteristics of peripheral lymphocyte PD-1 and FoxP3+ regulatory T cells (FoxP3+ Tregs) before and after surgery or chemotherapy in gastric cancer patients.

METHODS

Twenty-nine stomach cancer patients undergoing chemotherapy after a D2 gastrectomy provided 10 mL peripheral blood samples at each phase of the perioperative period and during chemotherapy. This study also included 29 age-matched healthy donors as a control group. PD-1 expression was detected on lymphocytes, including CD4+CD8+CD45RO+, CD4+CD45RO+, and CD8+CD45RO+ lymphocytes as well as regulatory T cells.

RESULTS

We observed a significant increase of PD-1 expression on immune subsets and a larger number of FoxP3+ Tregs in gastric cancer patients (P < 0.05). Following D2 gastrectomy, peripheral lymphocytes PD-1 expression and the number of FoxP3+ Tregs notably decrease (P < 0.05). However, during postoperative chemotherapy, we only observed a decrease in PD-1 expression on lymphocytes in the CD8+CD45RO+ and CD8+CD45RO+ populations. Additionally, linear correlation analysis indicated a positive correlation between PD-1 expression and the number of CD4+CD45RO+FoxP3high activated Tregs (aTregs) on the total peripheral lymphocytes (r = 0.5622, P < 0.0001).

CONCLUSION

The observed alterations in PD-1 expression and the activation of regulatory T cells during gastric cancer treatment may offer novel insights for future investigations into tumor immune evasion and the clinical application of anti-PD-1 antibodies in gastric cancer.

Helicobacter pylori promotes colorectal carcinogenesis by deregulating intestinal immunity and inducing a mucus-degrading microbiota signature

OBJECTIVE

Helicobacter pylori infection is the most prevalent bacterial infection worldwide. Besides being the most important risk factor for gastric cancer development, epidemiological data show that infected individuals harbour a nearly twofold increased risk to develop colorectal cancer (CRC). However, a direct causal and functional connection between H. pylori infection and colon cancer is lacking.

DESIGN

We infected two Apc-mutant mouse models and C57BL/6 mice with H. pylori and conducted a comprehensive analysis of H. pylori-induced changes in intestinal immune responses and epithelial signatures via flow cytometry, chip cytometry, immunohistochemistry and single cell RNA sequencing. Microbial signatures were characterised and evaluated in germ-free mice and via stool transfer experiments.

RESULTS

H. pylori infection accelerated tumour development in Apc-mutant mice. We identified a unique H. pylori-driven immune alteration signature characterised by a reduction in regulatory T cells and pro-inflammatory T cells. Furthermore, in the intestinal and colonic epithelium, H. pylori induced pro-carcinogenic STAT3 signalling and a loss of goblet cells, changes that have been shown to contribute-in combination with pro-inflammatory and mucus degrading microbial signatures-to tumour development. Similar immune and epithelial alterations were found in human colon biopsies from H. pylori-infected patients. Housing of Apc-mutant mice under germ-free conditions ameliorated, and early antibiotic eradication of H. pylori infection normalised the tumour incidence to the level of uninfected controls.

CONCLUSIONS

Our studies provide evidence that H. pylori infection is a strong causal promoter of colorectal carcinogenesis. Therefore, implementation of H. pylori status into preventive measures of CRC should be considered.

Do Elevated YKL-40 Levels Drive the Immunosuppressive Tumor Microenvironment in Colorectal Cancer? Assessment of the Association of the Expression of YKL-40, MMP-8, IL17A, and PD-L1 with Coexisting Type 2 Diabetes, Obesity, and Active Smoking

The influence of chitinase-3-like protein 1 (YKL-40 or CHI3L1) expression on the immunological properties of the tumor microenvironment, which may affect the effectiveness of immunotherapy, is currently not sufficiently understood in colorectal cancer (CRC). The aim of this study was to investigate the relationship between YKL-40 expression and the immunological properties of the tumor microenvironment in CRC. We performed in silico analysis, including analysis of immune cell infiltration scores and the immune landscape depending on YKL-40 expression, gene set enrichment analysis (GSEA), and analysis of three Gene Expression Omnibus (GEO) datasets. In 48 CRC tissue homogenates and the surgical margin, we analyzed the expression of YKL-40, MMP8, IL17A, and PD-L1. Moreover, we analyzed the expression of YKL-40 in tissue homogenates retrieved from patients with coexisting diabetes, obesity, and smoking. The expression of YKL-40 was significantly higher in CRC tumor tissue compared to healthy tissue and correlated with MMP-8, IL17A, and PD-L1 expression. In silico analysis revealed an association of YKL-40 with disease recurrence, and GSEA revealed a potential link between elevated YKL-40 expression and immunosuppressive properties of the tumor microenvironment in CRC.

Prediction of immunotherapy efficacy and immunomodulatory role of hypoxia in colorectal cancer

Immunotherapy has been used in the clinical treatment of colorectal cancer (CRC); however, most patients fail to achieve satisfactory survival benefits. Biomarkers with high specificity and sensitivity are being increasingly developed to predict the efficacy of CRC immunotherapy. In addition to DNA alteration markers, such as microsatellite instability/mismatch repair and tumor mutational burden, immune cell infiltration and immune checkpoints (ICs), epigenetic changes and no-coding RNA, and gut microbiomes all show potential predictive ability. Recently, the hypoxic tumor microenvironment (TME) has been identified as a key factor mediating CRC immune evasion and resistance to treatment. Hypoxia-inducible factor-1α is the central transcription factor in the hypoxia response that drives the expression of a vast number of survival genes by binding to the hypoxia response element in cancer and immune cells in the TME. Hypoxia regulates angiogenesis, immune cell infiltration and activation, expression of ICs, and secretion of various immune molecules in the TME and is closely associated with the immunotherapeutic efficacy of CRC. Currently, various agents targeting hypoxia have been found to improve the TME and enhance the efficacy of immunotherapy. We reviewed current markers commonly used in CRC to predict therapeutic efficacy and the mechanisms underlying hypoxia-induced angiogenesis and tumor immune evasion. Exploring the mechanisms by which hypoxia affects the TME will assist the discovery of new immunotherapeutic predictive biomarkers and development of more effective combinations of agents targeting hypoxia and immunotherapy.

Colorectal Cancer-Infiltrating Regulatory T Cells: Functional Heterogeneity, Metabolic Adaptation, and Therapeutic Targeting

Colorectal cancer (CRC) is a heterogeneous disease with one of the highest rates of incidence and mortality among cancers worldwide. Understanding the CRC tumor microenvironment (TME) is essential to improve diagnosis and treatment. Within the CRC TME, tumor-infiltrating lymphocytes (TILs) consist of a heterogeneous mixture of adaptive immune cells composed of mainly anti-tumor effector T cells (CD4+ and CD8+ subpopulations), and suppressive regulatory CD4+ T (Treg) cells. The balance between these two populations is critical in anti-tumor immunity. In general, while tumor antigen-specific T cell responses are observed, tumor clearance frequently does not occur. Treg cells are considered to play an important role in tumor immune escape by hampering effective anti-tumor immune responses. Therefore, CRC-tumors with increased numbers of Treg cells have been associated with promoting tumor development, immunotherapy failure, and a poorer prognosis. Enrichment of Treg cells in CRC can have multiple causes including their differentiation, recruitment, and preferential transcriptional and metabolic adaptation to the TME. Targeting tumor-associated Treg cell may be an effective addition to current immunotherapy approaches. Strategies for depleting Treg cells, such as low-dose cyclophosphamide treatment, or targeting one or more checkpoint receptors such as CTLA-4 with PD-1 with monoclonal antibodies, have been explored. These have resulted in activation of anti-tumor immune responses in CRC-patients. Overall, it seems likely that CRC-associated Treg cells play an important role in determining the success of such therapeutic approaches. Here, we review our understanding of the role of Treg cells in CRC, the possible mechanisms that support their homeostasis in the tumor microenvironment, and current approaches for manipulating Treg cells function in cancer.

Targeting interleukin-17 enhances tumor response to immune checkpoint inhibitors in colorectal cancer

Although immune checkpoint inhibitors (ICIs) have gained much attention in managing cancer, only a minority of patients, especially those with tumors that have been classified as immunologically "cold" such as microsatellite stable (MSS) colorectal cancers (CRC), experience clinical benefit from ICIs. Surprisingly, interleukin-17 (IL-17) and its primary source Th17 are enriched in CRC and inversely associated with patient outcome. Our previous study revealed that IL-17A could upregulate programmed death-ligand 1 (PD-L1) expression and impede the efficacy of immunotherapy. IL-17, therefore, can be a possible target to sensitize tumor cells to ICIs. The detailed clinical results from our trial, which is the first to show the benefits of the combination of anti-PD-1 with anti-IL-17 therapy for MSS CRC, have also been presented. In this review, we highlight the role of IL-17 in ICIs resistance and summarize the current clinical evidence for the use of combination therapy. Directions for future strategies to warm up immunologically "cold" MSS CRCs have also been proposed.

Rationalizing heptadecaphobia: TH 17 cells and associated cytokines in cancer and metastasis

Cancer is one of the leading causes of death worldwide. When cancer patients are diagnosed with metastasis, meaning that the primary tumor has spread to at least one different site, their life expectancy decreases dramatically. In the past decade, the immune system´s role in fighting cancer and metastasis has been studied extensively. Importantly, immune cells and inflammatory reactions generate potent antitumor responses but also contribute to tumor development. However, the molecular and cellular mechanisms underlying this dichotomic interaction between the immune system and cancer are still poorly understood. Recently, a spotlight has been cast on the distinct subsets of immune cells and their derived cytokines since evidence has implicated their crucial impact on cancer development. T helper 17 cell (TH 17) cells, which express the master transcriptional factor Retinoic acid-receptor-related orphan receptor gamma t, are among these critical cell subsets and are defined by their production of type 3 cytokines, such as IL-17A, IL-17F, and IL-22. Depending on the tumor microenvironment, these cytokines can also be produced by other immune cell sources, such as T cytotoxic 17 cell, innate lymphoid cells, NKT cells, or γδ T cells. To date, a lot of data have been collected describing the divergent functions of IL-17A, IL-17F, and IL-22 in malignancies. In this comprehensive review, we discuss the role of these TH 17- and non-TH 17-derived type 3 cytokines in different tumor entities. Furthermore, we will provide a structured insight into the strict regulation and subsequent downstream mechanisms of these cytokines in cancer and metastasis.

Relationship between Th17 immune response and cancer

Cancer is the second leading cause of death worldwide and epidemiological projections predict growing cancer mortality rates in the next decades. Cancer has a close relationship with the immune system and, although Th17 cells are known to play roles in the immune response against microorganisms and in autoimmunity, studies have emphasized their roles in cancer pathogenesis. The Th17 immune response profile is involved in several types of cancer including urogenital, respiratory, gastrointestinal, and skin cancers. This type of immune response exerts pro and antitumor functions through several mechanisms, depending on the context of each tumor, including the protumor angiogenesis and exhaustion of T cells and the antitumor recruitment of T cells and neutrophils to the tumor microenvironment. Among other factors, the paradoxical behavior of Th17 cells in this setting has been attributed to its plasticity potential, which makes possible their conversion into other types of T cells such as Th17/Treg and Th17/Th1 cells. Interleukin (IL)-17 stands out among Th17-related cytokines since it modulates pathways and interacts with other cell profiles in the tumor microenvironment, which allow Th17 cells to prevail in tumors. Moreover, the IL-17 is able to mediate pro and antitumor processes that influence the development and progression of various cancers, being associated with variable clinical outcomes. The understanding of the relationship between the Th17 immune response and cancer as well as the singularities of carcinogenic processes in each type of tumor is crucial for the identification of new therapeutic targets.

Cancer-associated fibroblast senescence and its relation with tumour-infiltrating lymphocytes and PD-L1 expressions in intrahepatic cholangiocarcinoma

BACKGROUND

Caveolin-1 (CAV1) in cancer-associated fibroblasts (CAFs) has pro- or anti-tumourigenic effect depending on the cancer type. However, its effect in intrahepatic carcinoma (ICC) remains unknown. Therefore, this study aimed to investigate the relationship between CAV1 in CAFs and tumour-infiltrating lymphocyte (TIL) numbers or PD-L1 levels in ICC patients.

METHODS

Consecutive ICC patients (n = 158) were enrolled in this study. The levels of CAV1 in CAFs, CD8 + TILs, Foxp3+ TILs and PD-L1 in cancer cells were analysed using immunohistochemistry. Their association with the clinicopathological factors and prognosis were evaluated. The correlation between these factors was evaluated.

RESULTS

CAV1 upregulation in CAFs was associated with a poor overall survival (OS) (P < 0.001) and recurrence-free survival (P = 0.008). Clinicopathological factors were associated with high CA19-9 levels (P < 0.001), advanced tumour stage (P = 0.046) and lymph node metastasis (P = 0.004). CAV1 level was positively correlated with Foxp3+ TIL numbers (P = 0.01). There were no significant correlations between CAV1 levels and CD8 + TIL numbers (P = 0.80) and PD-L1 levels (P = 0.97). An increased CD8 + TIL number and decreased Foxp3+ TIL number were associated with an increased OS. In multivariate analysis, positive CAV1 expression in CAFs (P = 0.013) and decreased CD8 + TIL numbers (P = 0.021) were independent poor prognostic factors.

CONCLUSION

Cellular senescence, represented by CAV1 levels, may be a marker of CAFs and a prognostic indicator of ICC through Foxp3+ TIL regulation. CAV1 expression in CAFs can be a therapeutic target for ICC.

Mir-124 Attenuates STAT3-Mediated TH17 Differentiation in Colitis-Driven Colon Cancer

Background

Inflammation often induces regeneration to repair the tissue damage. However, chronic inflammation can transform temporary hyperplasia into a fertile ground for tumorigenesis. Here, we demonstrate that the miR-124 acts as a safeguard to inhibit the pro-inflammatory production and reparative regeneration.

Methods

The expression levels of miR-124 and IL-17, IFN-γ were detected by qRT-PCR. TH17 or TH1 cells were detected by flow cytometer, respectively. The binding of STAT3 to the promoter region of IL-17 gene was analyzed by Chip assay. miR-124 binding to the 3′UTR of STAT3 gene was detected by reported plasmid construction and luciferase assay. Furthermore, DSS-induced colitis mice model and T cell transfer model were used to confirm the function of miR-124 in vivo. The related gene expression was analyzed by ELISA and western blot experiments.

Results

The results indicated that miR-124 decrease promotes colon tumorigenesis after Citrobacter rodentium infection and AOM/DSS induced colon cancer murine model. In molecular mechanism, miR-124 targets STAT3 to inhibit TH17 cell polarization and keep TH17 polarization in colonic microenvironment.

Conclusions

Our study strengthened the important role of miR-124 in the regulation of adaptive immune responses and blocking the development of colitis-related cancer.

Intestinal Regulatory T Cells

Mucosal surfaces are distinctive sites exposed to environmental, dietary, and microbial antigens. Particularly in the gut, the host continuously actively adapts via complex interactions between the microbiota and dietary compounds and immune and other tissue cells. Regulatory T cells (Tregs) are critical for tuning the intestinal immune response to self- and non-self-antigens in the intestine. Its importance in intestinal homeostasis is illustrated by the onset of overt inflammation caused by deficiency in Treg generation, function, or stability in the gut. A substantial imbalance in Tregs has been observed in intestinal tissue during pathogenic conditions, when a tightly regulated and equilibrated system becomes dysregulated and leads to unimpeded and chronic immune responses. In this chapter, we compile and critically discuss the current knowledge on the key factors that promote Treg-mediated tolerance in the gut, such as those involved in intestinal Treg differentiation, specificity and suppressive function, and their immunophenotype during health and disease. We also discuss the current state of knowledge on Treg dysregulation in human intestine during pathological states such as inflammatory bowel disease (IBD), necrotizing enterocolitis (NEC), graft-versus-host disease (GVHD), and colorectal cancer (CRC), and how that knowledge is guiding development of Treg-targeted therapies to treat or prevent intestinal disorders.

Distribution of Regulatory T-Cells and Other Phenotypes of T-Cells in Tumors and Regional Lymph Nodes of Colorectal Cancer Patients

BACKGROUND/AIM

Tumor microenvironments consist of many types of immune cells, in which regulatory T-cells (Tregs) are supposed to play important roles to suppress anti-tumor immunity. Regional lymph nodes are essential for antitumor immunity in colorectal cancer (CRC). In this study, we compared the diversity of phenotypes of T-cells in normal tissue and regional lymph nodes in order to determine the immunosuppressive mechanism of lymph node metastasis of CRC.

PATIENTS AND METHODS

Fifty patients were enrolled in this study, and paired samples (tumor tissue, normal tissue, and three regional lymph node samples and as well as non-regional lymph node samples) were obtained from each patient. In each paired-sample set, the proportions of different immune cell types and T-cells expressing immune checkpoint molecules were compared using flow cytometry.

RESULTS

Higher proportions of Tregs [7.58% (4.94%-13.87%) vs. 1.79% (0.03%-5.36%), p<0.001] and lower proportions of INFγ-producing CD4-positive T (iCD4+) cells [21.49% (12.08%-27.35%) vs. 26.55% (15.65%-37.63%), p<0.001] were observed in tumor tissue than in normal mucosa. Parts of regional lymph nodes nearest the tumor had a greater proportion of Tregs [5.86% (4.18%-7.69%)] and lower proportions of iCD4+ [5.94% (3.51%-9.04%)] and INFγ-producing CD8-positive T (iCD8+) cells [21.93% (14.92%-35.90%)] than distant parts of regional lymph nodes and non-regional lymph nodes. Both immune-suppressing molecules (CTLA-4 and PD-1) and immune-promoting molecules (OX-40 and ICOS) tended to be highly expressed in tumor tissue and local lymph nodes.

CONCLUSION

In patients with CRC, regional lymph nodes, especially the parts nearest the tumor, had a higher proportion of Tregs and other suppressive immunophenotypes of T-cells than those located more distantly.

Tumor Infiltrating Regulatory T Cells in Sporadic and Colitis-Associated Colorectal Cancer: The Red Little Riding Hood and the Wolf

Regulatory T cells represent a class of specialized T lymphocytes that suppress unwanted immune responses and size the activation of the immune system whereby limiting collateral damages in tissues involved by inflammation. In cancer, the accumulation of Tregs is generally associated with poor prognosis. Many lines of evidence indicate that Tregs accumulation in the tumor microenvironment (TME) suppresses the immune response against tumor-associated antigens (TAA), thus promoting tumor progression in non-small cell lung carcinoma (NSLC), breast carcinoma and melanoma. In colorectal cancer (CRC) the effect of Tregs accumulation is debated. Some reports describe the association of high number of Tregs in CRC stroma with a better prognosis while others failed to find any association. These discordant results stem from the heterogeneity of the immune environment generated in CRC in which anticancer immune response may coexists with tumor promoting inflammation. Moreover, different subsets of Tregs have been identified that may exert different effects on cancer progression depending on tumor stage and their location within the tumor mass. Finally, Tregs phenotypic plasticity may be induced by cytokines released in the TME by dysplastic and other tumor-infiltrating cells thus affecting their functional role in the tumor. Here, we reviewed the recent literature about the role of Tregs in CRC and in colitis-associated colorectal cancer (CAC), where inflammation is the main driver of tumor initiation and progression. We tried to explain when and how Tregs can be considered to be the "good" or the "bad" in the colon carcinogenesis process on the basis of the available data concluding that the final effect of Tregs on sporadic CRC and CAC depends on their localization within the tumor, the subtype of Tregs involved and their phenotypic plasticity.

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.

PD-L1 Induction by Cancer-Associated Fibroblast-Derived Factors in Lung Adenocarcinoma Cells

Cancer-associated fibroblasts (CAFs) exert various effects upon biological behaviours of cancer. In this study, we examined the correlation of CAFs with the intra-tumoural immune system in the lung adenocarcinoma microenvironment. We studied 27 and 113 cases of lung adenocarcinoma tentatively as Cohorts 1 and 2, respectively. The patients in Cohort 1 received epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) for recurrent lung adenocarcinoma. α-smooth muscle actin (α-SMA), a surrogate marker for CAFs, was examined by immunohistochemistry. We then examined the effects of CAFs isolated from lung cancer tissues on programmed death ligand 1 (PD-L1) expression in lung adenocarcinoma cell lines. No significant associations were detected between α-SMA status and the ratios of CD8/CD4 and Foxp3/CD8 in Cohort 1. However, α-SMA status was significantly associated with PD-L1 status in both Cohorts 1 and 2. Conditioned medium of CAFs significantly induced PD-L1 expression in lung adenocarcinoma cell lines, A549, PC-9, and H1975. Among the cytokines examined by antibody array, C-X-C motif chemokine ligand 2 (CXCL2) increased PD-L1 mRNA expression in these cell lines. CXCL2 is therefore considered to have a potential to induce PD-L1 expression in lung adenocarcinoma cells as a result of an interaction between carcinoma cells and CAFs. These findings did firstly demonstrate that CAFs indirectly influenced tumour immunity through increasing PD-L1 expression in lung adenocarcinoma cells.

Classical Hodgkin lymphoma cells may promote an IL-17-enriched microenvironment

In classical Hodgkin lymphoma (cHL), the significance of the interplay between Hodgkin and Reed-Sternberg cells (HRS) and reactive T cells remains poorly defined. By immunohistochemistry on bioptic cHL specimens, we found that HRS and surrounding T lymphocytes stained positive for IL-17 in 40% of cases. IL-17 was detectable in a similar proportion of patients' sera and correlated with disease burden. Supernatants of KM-H2 and HDLM-2 cHL cell lines guided preferential chemotaxis of CCR6⁺ T lymphocytes. Coculture of cHL cell lines with PBMC promoted the enrichment of Th17 lymphocytes and Foxp3⁺/IL-17⁺ cells, whereas T regulatory cells slightly decreased. Soluble CD30 downmodulated membrane CD30 expression on T cells and contributed to their polarization shift by stimulating IL-17 production and reducing IFN-γ synthesis. Thus, HRS and a number of reactive CD4⁺ T cells, attracted by tumor-secreted chemokines, produce an IL-17 tumor-shaped inflammatory milieu in a cHL subset.

Long-term prognostic significance of interleukin-17-producing T cells in patients with non-small cell lung cancer

The presence of interleukin (IL)‐17‐producing T cells has recently been reported in non‐small cell lung cancer (NSCLC) patients. However, the long‐term prognostic significance of these populations in NSCLC patients remains unknown. In the present study, we collected peripheral blood from 82 NSCLC patients and 22 normal healthy donors (NC). Percentages of IL‐17‐producing CD4⁺T (Th17), CD8⁺T (Tc17) and γδT cells (γδT17) were measured to determine their association with clinical outcomes and overall survival (OS) in NSCLC. All NSCLC patients were followed up until July 2018. Median follow‐up time was 13.5 months (range 1‐87 months). The 3‐ and 5‐year survival rate was 27% and 19.6%, respectively. We found that Th17 cells and γδT17 cells were significantly increased, whereas Tc17 cells were markedly decreased in patients with NSCLC compared with those in NC. In addition, Th17 cells were significantly positively associated with T helper type 1 cells (Th1), whereas γδT17 cells were significantly negatively associated with γδT ⁺ interferon (IFN)‐γ⁺ cells. High percentages of peripheral Tc17 cells were significantly associated with favorable 5‐year OS (P = .025), especially in patients with early TNM stage (P = .016). Furthermore, high percentages of peripheral Th17 cells were positively associated with favorable 5‐year OS in patients with late TNM stage (P = .002). However, no significant association was observed between γδT17 cells and OS, regardless of the TNM stage. In conclusion, our findings suggest that enhanced Th17 and reduced Tc17 cells in the peripheral blood could be a significant predictor of a favorable prognosis for NSCLC patients.

IL-17 and colorectal cancer: From carcinogenesis to treatment

Colorectal cancer (CRC) is one of the most common types of cancer in the world. Several factors contribute to the development of this cancer. Tumor formation in colon triggers immune responses such as immune cells proliferation, phenotype alteration, cytokine synthesis and release, which lead to IL-17 producing T cells, the differentiated CD4+ T cells i.e. T helper 17. IL-17 is a pro-inflammatory cytokine, which its level is up regulated in serum and tissues of CRC patients. Several studies have shown that IL-17 has an important role in metastasis and prognosis of CRC. The aim of this review is to summarize the role of this cytokine in tumorigenesis, angiogenesis and metastasis of CRC and discuss its value in diagnosis, prognosis and treatment of CRC.

Prognostic roles for IL-2-producing and CD69+ T cell subsets in colorectal cancer patients

Tumor infiltrating T cells are a predictor of patient outcome in patients with colorectal cancer (CRC). However, many T cell populations have been associated with both poor and positive patient prognoses, indicating a need to further understand the role of different T cell subsets in CRC. In this study, the T cell infiltrate from the tumor and nontumor bowel (NTB) was examined in 95 CRC patients using flow cytometry and associations with cancer stage and disease recurrence made. Our findings showed that IFN-γ-producing T cells were associated with positive patient outcomes, and CD69⁺ T cells were associated with disease recurrence. Inflammatory (IL-17) and regulatory T cells were not associated with disease recurrence. Surprisingly, in a second cohort of 32 patients with long-term clinical follow up data, tumor infiltrating IL-2-producing T cells correlated negatively with disease free survival (DFS) and a higher frequency of IL-2-producing T cells was found in the NTB of patients with poorly differentiated tumors. These results point toward the possibility of a negative impact of IL-2 in tumor immune responses, which may influence future immunotherapy treatments in CRC patients.

An Atlas of Human Regulatory T Helper-like Cells Reveals Features of Th2-like Tregs that Support a Tumorigenic Environment

Regulatory T cells (Tregs) play a pivotal role in maintaining immunological tolerance, but they can also play a detrimental role by preventing antitumor responses. Here, we characterized T helper (Th)-like Treg subsets to further delineate their biological function and tissue distribution, focusing on their possible contribution to disease states. RNA sequencing and functional assays revealed that Th2-like Tregs displayed higher viability and autocrine interleukin-2 (IL-2)-mediated activation than other subsets. Th2-like Tregs were preferentially found in tissues rather than circulation and exhibited the highest migratory capacity toward chemokines enriched at tumor sites. These cellular responses led us to hypothesize that this subset could play a role in maintaining a tumorigenic environment. Concurrently, Th2-like Tregs were enriched specifically in malignant tissues from patients with melanoma and colorectal cancer compared to healthy tissue. Overall, our results suggest that Th2-like Tregs may contribute to a tumorigenic environment due to their increased cell survival, higher migratory capacity, and selective T-effector suppressive ability.

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Memory Tregs can be classified as T helper-like Tregs (Th2, Th17, Th1, and Th1/17)

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Human Th2-like Tregs exhibit the highest viability and IL-2-mediated activation

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Th2-like Tregs are the subset with the highest chemotaxis toward CCL17/22

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Th2-like Tregs are enriched at tumor sites in melanoma and colorectal cancer

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.

The attenuation of renal fibrosis by histone deacetylase inhibitors is associated with the plasticity of FOXP3+IL-17+ T cells

BACKGROUND

The histone deacetylase (HDAC) inhibitor, which has potential effects on epigenetic modifications, had been reported to attenuate renal fibrosis. CD4⁺ forkhead box P3 (FOXP3)⁺ T regulatory (Treg) cells may be converted to inflammation-associated T helper 17 cells (Th17) with tissue fibrosis properties. The association between FOXP3⁺IL-17⁺ T cells and the attenuation of renal fibrosis by the HDAC inhibitor is not clear.

METHODS

This study evaluated the roles of the HDAC inhibitor, Treg cells and their differentiation into Th17 cells, which aggravate chronic inflammation and renal fibrosis in a unilateral ureteral obstruction (UUO) mouse model. The study groups included control and UUO mice that were monitored for 7, 14 or 21 days.

RESULTS

Juxtaglomerular (JG) hyperplasia, angiotensin II type 1 receptor (AT1R) expression and lymphocyte infiltration were observed in renal tissues after UUO but were decreased after trichostatin A (TSA) treatment, a HDAC inhibitor. The number of CD4⁺FOXP3⁺ T cells increased progressively, along with the number of FOXP3⁺interleukin (IL)-17⁺ T cells, after 14 days, and their numbers then progressively decreased with increasing CD4⁺IL-17⁺ T cell numbers, as demonstrated by double immunohistochemistry. Progressive renal fibrosis was associated with the loss of CD4⁺FOXP3⁺IL-17⁺ T cells in splenic single-cell suspensions. FOXP3⁺IL-17⁺ T cells expressed TGF-β1 both in vitro and in vivo, and TGF-β1 expression was significantly knockdown by IL-17 siRNA in vitro. These cells were found to play a role in converting Tregs into IL-17- and TGF-β1-producing cells.

CONCLUSIONS

TSA treatment decreased JG hyperplasia, the percentage of FOXP3⁺IL-17⁺ cells and the degree of fibrosis, suggesting that therapeutic benefits may result from epigenetic modifications.

Pro-Tumor and Anti-Tumor Functions of IL-17 and of TH17 Cells in Tumor Microenvironment

The current review reveals the seven subclasses of CD4+ T helper cells, i.e. Th1, Th2, Th9, Th17, Th22, regulatory T cells and Tfh, the cytokines produced by them and their role in tumor microenvironment. Main attention was paid to IL-17 and Th17 cells. IL-17-producing cells were described, among which were Treg17 cells and Tc17 cells. The transcription factors, engaged in the activation of Th17 cell differentiation were reviewed. It was shown that Th17 cells might possess regulatory functions in tumor microenvironments that directs toward immunosuppression. The reciprocity between Treg and Th17 cells is realized when the production of a large amount of TGF-β in tumors causes Treg cell differentiation, and the addition of IL-6 shifts the differentiation of naïve T cells to Th17 cells. The main pro-tumor role of IL-17 is the promotion of tumor angiogenesis through stimulation of fibroblasts and endothelial cells. The antitumor functions of IL-17 are associated with enhancement of cytotoxic activity of tumor specific CTL cells and with angiogenesis that provide channels through which immune cells might invade tumor and promote antitumor immunity.

IL-17A Levels in the Sera of Patients with Gastric Cancer Show Limited Elevation

BACKGROUND

Inflammation plays a major role in the development and progression of gastric and other gastrointestinal tumors. The IL-17 family of cytokines has been under investigation as targets of immunotherapy.

MATERIALS AND METHODS

We investigated the levels of IL-17A inflammatory cytokine in the sera of 57 patients with gastric cancer (GC) and 90 healthy age/sex matched controls using ELISA methods.

RESULTS

In only 5 (8.8%) of the patients' sera was IL-17A detectable. No IL-17A was apparent in the sera of healthy controls. The maximum concentration of IL-17A in patients was 7.004 pg/ml. Vascular and lymphatic invasions were only seen in one of the 5 positive cases. Although all of them were in the age group >60 years, no correlation was seen between age and IL-17A level. These results are somewhat different from our findings for colorectal cancer (CRC) in the same population.

CONCLUSIONS

It is possible that the inflammopathology of CRC and GC are rather different, at least in Fars, a southern province of Iran.

Interleukin-17 acts as double-edged sword in anti-tumor immunity and tumorigenesis

Interleukin-17 (IL-17), a proinflammatory cytokine, mainly produced by Th17 cells, participates in both innate and adaptive immune responses and is involved in various diseases, including infectious diseases, autoimmune disorders and cancer. Emerging evidence indicates that IL-17 not only has an oncogenic role in tumorigenesis by regulating tumor angiogenesis and enhancing tumor immune evasion but also exerts anti-tumor functions by enhancing natural killer (NK) cells and cytotoxic T lymphocytes (CTLs) activation and through the recruitment of neutrophils, NK cells and CD4⁺ and CD8⁺ T cells to tumor tissue. In this review, we provide an overview on the basic biology of IL-17 and recent findings regarding its enigmatic double-edged features in tumorigenesis, with special attention to the roles of IL-17 produced by tumor cells interacting with other factors in the tumor microenvironment.

Th17 Cell Plasticity and Functions in Cancer Immunity

Th17 cells represent a particular subset of T helper lymphocytes characterized by high production of IL-17 and other inflammatory cytokines. Th17 cells participate in antimicrobial immunity at mucosal and epithelial barriers and particularly fight against extracellular bacteria and fungi. While a role for Th17 cells in promoting inflammation and autoimmune disorders has been extensively and elegantly demonstrated, it is still controversial whether and how Th17 cells influence tumor immunity. Although Th17 cells specifically accumulate in many different types of tumors compared to healthy tissues, the outcome might however differ from a tumor type to another. Th17 cells were consequently associated with both good and bad prognoses. The high plasticity of those cells toward cells exhibiting either anti-inflammatory or in contrast pathogenic functions might contribute to Th17 versatile functions in the tumor context. On one hand, Th17 cells promote tumor growth by inducing angiogenesis (via IL-17) and by exerting themselves immunosuppressive functions. On the other hand, Th17 cells drive antitumor immune responses by recruiting immune cells into tumors, activating effector CD8(+) T cells, or even directly by converting toward Th1 phenotype and producing IFN-γ. In this review, we are discussing the impact of the tumor microenvironment on Th17 cell plasticity and function and its implications in cancer immunity.

Vaccination of multiple myeloma: Current strategies and future prospects

Tumor immunotherapy holds great promise in controlling multiple myeloma (MM) and may provide an alternative treatment modality to conventional chemotherapy for MM patients. For this reason, a major area of investigation is the development of cancer vaccines to generate myeloma-specific immunity. Several antigens that are able to induce specific T-cell responses are involved in different critical mechanisms for cell differentiation, inhibition of apoptosis, demethylation and proliferation. Strategies under development include infusion of vaccine-primed and ex vivo expanded/costimulated autologous T cells after high-dose melphalan, genetic engineering of autologous T cells with receptors for myeloma-specific epitopes, administration of dendritic cell/plasma cell fusions and administration expanded marrow-infiltrating lymphocytes. In addition, novel immunomodulatory drugs may synergize with immunotherapies. The task ahead is to evaluate these approaches in appropriate clinical settings, and to couple them with strategies to overcome mechanisms of immunoparesis as a means to induce more robust clinically significant immune responses.

Deubiquitinase DUBA is a post-translational brake on interleukin-17 production in T cells

T-helper type 17 (TH17) cells that produce the cytokines interleukin-17A (IL-17A) and IL-17F are implicated in the pathogenesis of several autoimmune diseases. The differentiation of TH17 cells is regulated by transcription factors such as RORγt, but post-translational mechanisms preventing the rampant production of pro-inflammatory IL-17A have received less attention. Here we show that the deubiquitylating enzyme DUBA is a negative regulator of IL-17A production in T cells. Mice with DUBA-deficient T cells developed exacerbated inflammation in the small intestine after challenge with anti-CD3 antibodies. DUBA interacted with the ubiquitin ligase UBR5, which suppressed DUBA abundance in naive T cells. DUBA accumulated in activated T cells and stabilized UBR5, which then ubiquitylated RORγt in response to TGF-β signalling. Our data identify DUBA as a cell-intrinsic suppressor of IL-17 production.

Detailed characterization of tumor infiltrating lymphocytes in two distinct human solid malignancies show phenotypic similarities

Background

We examined the phenotype and function of lymphocytes collected from the peripheral blood (PBL) and tumor (TIL) of patients with two different solid malignancies: colorectal cancer liver metastases (CRLM) and ovarian cancer (OVC).

Methods

Tumor and corresponding peripheral blood were collected from 16 CRLM and 22 OVC patients; immediately following resection they were processed and analyzed using a multi-color flow cytometry panel. Cytokine mRNA from purified PBL and TIL CD4⁺ T cells were also analyzed by qPCR.

Results

Overall, we found similar changes in the phenotypic and cytokine profiles when the TIL were compared to PBL from patients with two different malignancies. The percentage of Treg (CD4⁺/CD25⁺/FoxP3⁺) in PBL and TIL was similar: 8.1% versus 10.2%, respectively in CRLM patients. However, the frequency of Treg in primary OVC TIL was higher than PBL: 19.2% versus 4.5% (p <0.0001). A subpopulation of Treg expressing HLA-DR was markedly increased in TIL compared to PBL in both tumor types, CRLM: 69.0% versus 31.7% (p = 0.0002) and OVC 74.6% versus 37.0% (p <0.0001), which suggested preferential Treg activation within the tumor. The cytokine mRNA profile showed that IL-6, a cytokine known for its immunosuppressive properties through STAT3 upregulation, was increased in TIL samples in patients with OVC and CRLM. Both TIL populations also contained a significantly higher proportion of activated CD8⁺ T cells (HLA-DR⁺/CD38⁺) compared to PBL (CRLM: 30.2% vs 7.7%, (p = 0.0012), OVC: 57.1% vs 12.0%, (p <0.0001)).

Conclusion

This study demonstrates that multi-color flow cytometry of freshly digested tumor samples reveals phenotypic differences in TIL vs PBL T cell sub-populations. The TIL composition in primary and metastatic tumors from two distinct histologies were remarkably similar, showing a greater proportion of activated/suppressive Treg (HLA-DR⁺, CD39⁺, CTLA-4⁺ and Helios⁺) and activated cytotoxic T cells (CD8⁺/HLA-DR⁺/CD38⁺) when compared to PBL and an increase in IL-6 mRNA from CD4 TIL.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-014-0038-9) contains supplementary material, which is available to authorized users.

IL-17+Foxp3+ T cells: an intermediate differentiation stage between Th17 cells and regulatory T cells

Foxp3(+) Tregs have been known as a major regulator of immune homeostasis through their immunosuppressive function. Th17 lineage is a CD4(+) T cell subset that exerts its function by secreting proinflammatory cytokines and protecting host against microbial infections. The altered ratio between Foxp3(+) Tregs and Th17 cells plays an important role in the pathogenesis of immune-related diseases. Recent mice and human studies have demonstrated that Tregs can be reprogrammed into a novel population, IL-17(+)Foxp3(+) T cells, phenotypically and functionally resembling Th17 cells under the complicated cytokine stimulation. The identification of IL-17(+)Foxp3(+) T cells may provide a new understanding of therapy targeting Tregs and Th17 cells in autoimmune diseases and cancer. Here, we highlight significant data regarding the phenotype profile, origination, differentiation, and the pleiotropic functions of IL-17(+)Foxp3(+) T cells and the reciprocal relationships of these cells to Tregs and Th17 cells. Furthermore, the role of IL-17(+)Foxp3(+) T cells in tumorigenesis and clinical implications in cancer therapy are discussed in this review.

Significant association between IL23R and IL17F polymorphisms and clinical features of colorectal cancer

Th17cells are involved in inflammatory and autoimmune diseases. These cells may be involved in pathological processes mainly producing pro-inflammatory cytokines. Recently, it was shown that the IL23/IL17 pathway plays an important role in the development of inflammatory bowel disease. In general, genes encoding cytokines are genetically polymorphic and polymorphisms in genes IL23R el IL17F were shown associated with susceptibility to Crohn's disease and ulcerative colitis which in their turn are considered as risk factors for developing colorectal cancer (CRC). Our approach is to study IL17F and IL23R polymorphisms as risk factor associated with CRC in the Tunisian population in patients and healthy controls. Interesting, we noted a significant association between IL17F and IL23R polymorphisms and tumor location (p=0.0001 and p=0.049, respectively), tumor histology (p=0.007 and p=0.049, respectively) and tumor architecture (p=0.0000000001 and p=0.07, respectively) in CRC patients. We also showed a significant association of IL17F variant with an increased risk of TNM stage III/IV (p=0.007), showing an increased risk of advanced stage. Finally, we observed a positive link between IL17F polymorphism and CRC patients with lymph nodes (p=0.0000000001) and metastasis (p=0.00000009). However, we found no evidence to support a significant association between IL17F and IL23R polymorphisms and colorectal cancer susceptibility. Our findings suggest that IL17F and IL23R polymorphisms were significantly associated with clinical features variables. The IL17F cytokine appear to be involved in the control of tumor growth and invasion of gastrointestinal tumors. IL17 and IL23 polymorphisms or those of their receptors as important determinants of susceptibility to colorectal cancer are still subject to questioning.

Interleukin-17: a promoter in colorectal cancer progression

It is widely accepted that chronic inflammation plays an active role in cancer. Inflammatory immunocytes and related cytokines in the tumor microenvironment are supposed to be a “double-edged sword” in colorectal cancer (CRC) initiation and progression. Interleukin-17 (IL-17), a pleiotropic proinflammatory cytokine, can promote cancer-elicited inflammation and prevent cancer cells from immune surveillance. Despite controversy, IL-17 is generally considered to be a promoter in CRC progression. In this review, we devote to summarize the current progress regarding the role of IL-17 in tumor initiation and progression, as well as the prognostic value in CRC.

The role of IL-17-producing Foxp3+ CD4+ T cells in inflammatory bowel disease and colon cancer

The intestinal epithelium and underlying lamina propria contain T cells that play important roles in maintaining colonic homeostasis. These T cells mediate substantial and specific regulation to ensure that pathogenic microorganisms are eliminated while commensal bacteria are tolerated. There is considerable evidence supporting the notion that the altered ratio between Foxp3(+)CD4(+) T regulatory cells and T effector cells in the colonic microenvironment might contribute to the initiation and progression of inflammation and eventually development of colon cancer. Recent findings on the heterogeneity and plasticity of T regulatory cells, such as the identification of IL-17(+)Foxp3(+)CD4(+) and the RORγt(+)Foxp3(+)CD4(+) subsets, in patients with colorectal inflammation and cancer have provided a new twist in our understanding of the pathogenesis of colonic diseases. Phenotypic and functional properties of IL-17-producing Foxp3(+)CD4(+) T cells as well as the significant implications of these cells in the initiation and progression of colorectal diseases are discussed in this review.

Th inducing POZ-Kruppel Factor (ThPOK) is a key regulator of the immune response since the early steps of colorectal carcinogenesis

We purposed to evaluate the role of Th inducing POZ-Kruppel Factor (ThPOK), a transcriptional regulator of T cell fate, in tumour-induced immune system plasticity in colorectal carcinogenesis. The amounts of CD4+, CD8+ and CD56+ and ThPOK+ cells infiltrate in normal colorectal mucosa (NM), in dysplastic aberrant crypt foci (microadenomas, MA), the earliest detectable lesions in colorectal carcinogenesis, and in colorectal carcinomas (CRC), were measured, and the colocalization of ThPOK with the above-mentioned markers of immune cells was evaluated using confocal microscopy. Interestingly, ThPOK showed a prominent increase since MA. A strong colocalization of ThPOK with CD4 both in NM and in MA was observed, weaker in carcinomas. Surprisingly, there was a peak in the colocalization levels of ThPOK with CD8 in MA, which was evident, although to a lesser extent, in carcinomas, too. In conclusion, according to the data of the present study, ThPOK may be considered a central regulator of the earliest events in the immune system during colorectal cancer development, decreasing the immune response against cancer cells.

Basic principles of tumor-associated regulatory T cell biology

Due to the critical role of forkhead box (Fox)p3(+) regulatory T cells (Tregs) in the regulation of immunity and the enrichment of Tregs within many human tumors, several emerging therapeutic strategies for cancer involve the depletion or modulation of Tregs, with the aim of eliciting enhanced antitumor immune responses. Here, we review recent advances in understanding of the fundamental biology of Tregs, and discuss the implications of these findings for current models of tumor-associated Treg biology. In particular, we discuss the context-dependent functional diversity of Tregs, the developmental origins of these cells, and the nature of the antigens that they recognize within the tumor environment. In addition, we highlight critical areas of focus for future research.

Anti-cancer versus cancer-promoting effects of the interleukin-17-producing T helper cells

Research on T helper 17 (Th17) cells with regard to immunoediting has revealed elusive results. Whereas enhanced Th17 response and related molecules such as interleukin (IL)-17, IL-21, IL-22, IL-23 and STAT3 accompanied tumor induction and progression, finding that tumor growth/stage was negatively correlated with increased infiltration of Th17 cells in the tumor mass has prompted elucidation of various antitumor mechanisms elicited by Th17 and their related molecules. The pro-tumor efficacy of Th17 response included promotion of neutrophilia and induction of angiogenic (e.g. VEGF, MMP2 and MMP9) and anti-apoptotic factors (e.g. Bcl-XL), as well as expansion and activation of myeloid-derived suppressor cells, which facilitate generation of tumor-specific regulatory T cells. Other tumor immunogenic settings revealed anti-tumor pathways including induction of cytotoxic activity, expression of MHC antigens, the ability Th17 cells to reside within the tumor, and to convert into IFN-γ producers. Notably, Th17 cell related molecules exert indirect pro- or anti-tumor effects via inducing viral persistence or mediating protective mechanisms against bacterial and viral infection. Herein, the recent literature revealing such immunoediting events mediated by Th17 cells and their associated molecules as delivered by various experimental regimens and observed in cancer patient are revised, with a focus on some proposed anti-cancer therapies.

Regulatory T cells in inflammatory bowel diseases and colorectal cancer

Regulatory T cells (T(regs)) are key elements in immunological self-tolerance. The number of T(regs) may alter in both peripheral blood and in colonic mucosa during pathological circumstances. The local cellular, microbiological and cytokine milieu affect immunophenotype and function of T(regs). Forkhead box P3+ T(regs) function shows altered properties in inflammatory bowel diseases (IBDs). This alteration of T(regs) function can furthermore be observed between Crohn's disease and ulcerative colitis, which may have both clinical and therapeutical consequences. Chronic mucosal inflammation may also influence T(regs) function, which together with the intestinal bacterial flora seem to have a supporting role in colitis-associated colorectal carcinogenesis. T(regs) have a crucial role in the immunoevasion of cancer cells in sporadic colorectal cancer. Furthermore, their number and phenotype correlate closely with the clinical outcome of the disease, even if their contribution to carcinogenesis has previously been controversial. Despite knowledge of the clinical relationship between IBD and colitis-associated colon cancer, and the growing number of immunological aspects encompassing sporadic colorectal carcinogenesis, the molecular and cellular links amongst T(regs), regulation of the inflammation, and cancer development are still not well understood. In this paper, we aimed to review the current data surrounding the role of T(regs) in the pathogenesis of IBD, colitis-associated colon cancer and sporadic colorectal cancer.

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.