IL-17A in the tumor microenvironment of the human colorectal adenoma-carcinoma sequence

Interleukin-17: A pleiotropic cytokine implicated in inflammatory, infectious, and malignant disorders

IL-17A, referred to as IL-17, is the founding member of a family of pro-inflammatory cytokines, including IL-17B, IL-17C, IL-17D, IL-17E (or IL-25), and IL-17F, which act via receptors IL-17RA to IL-17RE, and elicit potent cellular responses that impact diverse diseases. IL-17's interactions with various cytokines include forming a heterodimer with IL-17F and being stimulated by IL-23's activation of Th17 cells, which can lead to inflammation and autoimmunity. IL-17 is implicated in infectious diseases and inflammatory disorders such as rheumatoid arthritis and psoriasis, promoting neutrophil recruitment and anti-bacterial immunity, but potentially exacerbating fungal and viral infections, revealing its dual role as protective and pathologic. IL-17 is also involved in various cancers, including breast, colon, cervical, prostate, and skin cancer, contributing to proliferation, immune invasion, and metastases, but also playing a protective role in certain instances. Four FDA-approved drugs-secukinumab (for ankylosing spondylitis, enthesitis-related arthritis, hidradenitis suppurativa, non-radiographic axial spondyloarthritis, plaque psoriasis, and psoriatic arthritis), ixekizumab (for ankylosing spondylitis, non-radiographic axial spondyloarthritis, plaque psoriasis, and psoriatic arthritis), brodalumab (for plaque psoriasis), and bimekizumab (for plaque psoriasis)-suppress the IL-17 pathway, with more in development, including netakimab, sonelokimab, izokibep, and CJM112. These agents and others are being studied across a spectrum of disorders. Understanding the complicated interplay between IL-17 and other immune mediators may yield new treatments for inflammatory/autoimmune conditions and malignancies.

The role of interleukin 17 in cancer: a systematic review

Interleukin 17 (IL17) is a cytokine involved in immune regulation and has been increasingly recognized for its role in cancer progression. This systematic review aims to integrate data on IL17's role in various tumors to better understand its implications for cancer prognosis and treatment. The review included 105 studies (27.6% experimental and 72.4% clinical). Clinical studies involved 9266 patients: 31.2% males, 60.0% females, and 8.8% with undefined gender. IL17A and IL17 were the most studied subtypes (36.2% and 33.3%, respectively). Breast cancer (26.7%), colorectal carcinoma (13.3%), and hematologic malignancies (10.5%) were the most researched neoplasms. IL17A promoted tumor growth in breast cancer and correlated with poor outcomes in colorectal, breast, and lung cancers. IL17 also played a significant role in immune modulation in gliomas and other tumors. IL17A significantly influences tumor growth and prognosis across various cancers, with notable roles in immune modulation and poor outcomes in multiple cancer types.

Th9 and Th17 Cells in Human Ulcerative Colitis-Associated Dysplastic Lesions

Background

Inflammation is the most important deriving force for the development of colitis-associated colorectal cancer (CAC) through the Inflammation-Pretumor dysplasia-CAC sequence. T helper (Th) subsets Th9 and Th17 cells can potentially stimulate inflammation in the ulcerative colitis (UC). Therefore, Th9 and Th17 cells may play a promoting role in the colitis-associated dysplasia (CAD).

Methods

Using immunohistochemistry (IHC), we evaluated the presentation patterns and densities of T lymphocytes, Th9 and Th17 cells in human UC and CAD tissues.

Results

A general increasing trend of CD3-positive T lymphocytes, P.U.1-positive Th9 and interleukin (IL)-17A-positive Th17 cells was illustrated throughout the normal-UC-CAD sequence, IHC images showed that these cells were very prominent in the lamina propria, and some cells were also observed in the epithelium in the CAD tissues. Density analysis revealed that numbers of Th9 and Th17 cells were progressively increased in the CAD tissues as compared with the UC and control tissues. In general, densities of Th9 and Th17 cells in the lamina propria were slightly higher in the non-adenoma-like dysplasia (NALD) tissues than that in the adenoma-like dysplasia (ALD) tissues. However, densities of neither Th9 nor Th17 cells in both the ALD and NALD subgroups were associated with the degree of dysplasia in CAD lesions.

Conclusion

Accumulated Th9 and Th17 cells contribute to the immune cellular composition in the CAD tissues and may represent the early conditional change for the Dysplasia-CAC transition.

Th17 cell function in cancers: immunosuppressive agents or anti-tumor allies?

T helper (Th) 17 cells, a distinct subset of Th lymphocytes, are known for their prominent interleukin (IL)-17 production and other pro-inflammatory cytokines. These cells exhibit remarkable plasticity, allowing them to exhibit different phenotypes in the cancer microenvironment. This adaptability enables Th17 cells to promote tumor progression by immunosuppressive activities and angiogenesis, but also mediate anti-tumor immune responses through employing immune cells in tumor setting or even by directly converting toward Th1 phenotype and producing interferon-gamma (IFN-γ). This dual role of Th17 cells in cancer makes it a double-edged sword in encountering cancer. In this review, we aim to elucidate the complexities of Th17 cell function in cancer by summarizing recent studies and, ultimately, to design novel therapeutic strategies, especially targeting Th17 cells in the tumor milieu, which could pave the way for more effective cancer treatments.

Narciclasine induces colon carcinoma cell apoptosis by inhibiting the IL-17A/Act1/TRAF6/NF-κB signaling pathway

IL-17 A is a promoter of colorectal cancer initiation and progression. Narciclasine is a polyhydroxy alkaloid compound isolated from Narcissus plants, which has potent anti-inflammatory and antitumor actions. The effects of narciclasine on colorectal tumors were evaluated, with a focus on IL-17 A. Narciclasine reduced the growth of HCT-116 and SW-480 colon cancer cells in vitro and in vivo in murine xenografts. The results of flow cytometry on JC-1 and Annexin V/PI revealed that narciclasine significantly reduced the mitochondrial membrane potential and induced apoptosis, findings confirmed by western blotting results of reduced Bcl-2 and enhanced Bax expression, as well as accumulation of cleaved Caspase-3, Caspase-8, Caspase-9, and cytoplasmic Cytochrome-c. After narciclasine incubation, IL-17 A, Act1, and TRAF6 were down-regulated, while p-P65 (Ser536) accumulated in the cytoplasm, a finding confirmed by laser scanning confocal microscopy. IL17A substitution could partly reverse these narciclasine effects while they were elevated by IL17A silencing. Moreover, IL-17 A, Act1, and TRAF6 were significantly expressed to greater extents in human colorectal cancer compared to normal adjacent tissue specimens and were closely linked with a poor prognosis. This study provided evidence that narciclasine may be a useful therapeutic drug for colorectal cancer treatment through its actions in down-regulating the L-17A/Act1/TRAF6/NF-κB anti-apoptotic signaling pathway.

The role of IL-17 in the pathogenesis and treatment of glioblastoma-an update on the state of the art and future perspectives

Glioblastoma (GBM) is the most common malignant brain tumor, which, despite significant progress made in the last years in the field of neuro-oncology, remains an incurable disease. GBM has a poor prognosis with a median survival of 12-15 months, and its aggressive clinical course is related to rapid growth, extensive infiltration of adjacent tissues, resistance to chemotherapy, radiotherapy and immunotherapy, and frequent relapse. Currently, several molecular biomarkers are used in clinical practice to predict patient prognosis and response to treatment. However, due to the overall unsatisfactory efficacy of standard multimodal treatment and the remaining poor prognosis, there is an urgent need for new biomarkers and therapeutic strategies for GBM. Recent evidence suggests that GBM tumorigenesis is associated with crosstalk between cancer, immune and stromal cells mediated by various cytokines. One of the key factors involved in this process appears to be interleukin-17 (IL-17), a pro-inflammatory cytokine that is significantly upregulated in the serum and tissue of GBM patients. IL-17 plays a key role in tumorigenesis, angiogenesis, and recurrence of GBM by activating pro-oncogenic signaling pathways and promoting cell survival, proliferation, and invasion. IL-17 facilitates the immunomodulation of the tumor microenvironment by promoting immune cells infiltration and cytokine secretion. In this article we review the latest scientific reports to provide an update on the role of IL-17 role in tumorigenesis, tumor microenvironment, diagnosis, prognosis, and treatment of GBM.

Increased circulating regulatory T cells and decreased follicular T helper cells are associated with colorectal carcinogenesis

Objective

Colorectal cancer (CRC) is the third most prevalent cancer worldwide and is associated with high morbidity and mortality rates. Colorectal carcinogenesis occurs via the conventional adenoma-to-carcinoma and serrated pathways. Conventional T helper (Th) and innate lymphoid cells (ILCs) play vital roles in maintaining intestinal homeostasis. However, the contribution of these two major lymphoid cell populations and their associated cytokines to CRC development is unclear. Therefore, we aimed to analyze peripheral lymphocyte profiles during colorectal carcinogenesis.

Methods

We collected 86 blood samples concurrently, and pathologists confirmed the presence of various pathological conditions (i.e., HPs, adenoma, and carcinoma) using hematoxylin and eosin staining. Ten healthy donors were recruited as healthy controls (HCs) from the physical examination center. We performed flow cytometry on peripheral blood mononuclear cells collected from patients with various pathological conditions and the HCs, and cytokines (interleukin-2, interleukin-4, interleukin-5, interleukin-13, interleukin-17A, interleukin-17F, interleukin-22, interferon-γ, and tumor necrosis factor-α) were quantified. We also analyzed the published single-cell RNA sequence data derived from tissue samples from different stages of colorectal carcinogenesis.

Results

The cytokine response in peripheral CD4+ T cells was upregulated during the carcinoma process. The frequency of peripheral regulatory T cells (Tregs) increased in the adenoma and carcinoma stages. While the T follicular helper (Tfh) cell proportion was downregulated in the adenoma and carcinoma processes. Thus, Th cell subsets, especially Tregs and Tfh cells, were involved in colonic diseases. Moreover, the immunological profile characteristics in the HPs were clarified.

Conclusion

We comprehensively analyzed circulating ILCs and adaptive T-cell lymphocyte subtypes in colorectal carcinoma progression. Our results show the immunological profile characteristics and support the involvement of Th subsets, especially Treg and Tfh cell populations, in colonic diseases. These findings significantly enhance our understanding of the immune mechanisms underlying CRC and its precancerous lesions. Further investigation of the Treg and Tfh cells' function in colorectal disease development will provide potential therapeutic targets for monitoring and preventing CRC development.

Interaction between Gut Microbiota and Dendritic Cells in Colorectal Cancer

Colorectal cancer (CRC) is a malignancy that manifests in serial stages and has been observed to have an escalating incidence in modern societies, causing a significant global health problem. The development of CRC is influenced by various exogenous factors, including lifestyle, diet, nutrition, environment, and microbiota, that can affect host cells, including immune cells. Various immune dysfunctions have been recognized in patients with CRC at different stages of this disease. The signature of microbiota in the development of CRC-inflammation related to obesity, diet, and reactive host cells, such as dendritic cells (DCs)-has been highlighted by many studies. This study focuses on DCs, the primary cellular mediators linking innate and adaptive immune responses against cancer. In addition, this review focuses on the role of microbiota in dysbiosis and how it affects DCs and, in turn, the immune response and progression of CRC by stimulating different sets of T cells. Additionally, DCs' role in protecting this delicate balance is examined. This is to determine how gene yields of commensal microbiota may be critical in restoring this balance when disrupted. The stages of the disease and major checkpoints are discussed, as well as the role of the C-type lectin receptor of immature DCs pattern recognition receptor in CRC. Finally, based on a thorough examination of worldwide clinical studies and recent advancements in cancer immunotherapy, it is recommended that innovative approaches that integrate DC vaccination strategies with checkpoint inhibitors be considered. This approach holds great promise for improving CRC management.

Colorectal Liver Metastasis: Can Cytokines Make the Difference?

Colorectal cancer (CRC) is the third leading cause of cancer-related death worldwide. Metastasis is the prime driver of CRC-related mortality, and the liver is the organ most frequently involved. Despite the overall success of current treatments, colorectal liver metastasis (CRLM) is associated with poor prognoses and a survival rate of only 14%. Recent studies have highlighted the importance of the tumor microenvironment (TME) and the crosstalk within it in determining the invasion of distant organs by circulating cancer cells. In the TME, cellular communication is mediated via soluble molecules, among which cytokines have recently emerged as key regulators, involved in every aspect of tumor progression and the metastatic cascade. Indeed, in the serum of CRC patients elevated levels of several cytokines are associated with cancer development and progression. The current review evaluates the role of different cytokines during CRLM development. Additionally, considering the increasing amount of data concerning the importance of cytokine complex networks, we outline the potential of combination treatments using targeted cytokines together with other well-established therapies, such as immune checkpoint blockades, chemotherapy, or gene therapy, to improve therapeutic outcomes.

RORγT agonists as immune modulators in anticancer therapy

RORγT is a transcription factor that directs the development of Th17 lymphocytes and other IL-17-expressing cells (e.g., Tc17 and ILC3 cells). These cells are involved in the body's defense against pathogenic bacteria and fungi, but they also participate in maintaining the proinflammatory environment in some autoimmune diseases and play a role in the immune system's response to cancer. Similar to other members of the nuclear receptor superfamily, the activity of RORγT is regulated by low-molecular-weight ligands. Therefore, extensive efforts have been dedicated to identifying inverse agonists that diminish the activity of this receptor and subsequently inhibit the development of autoimmune diseases. Unfortunately, in the pursuit of an ideal inverse agonist, the development of agonists has been overlooked. It is important to remember that these types of compounds, by stimulating lymphocytes expressing RORγT (Th17 and Tc17), can enhance the immune system's response to tumors. In this review, we present recent advancements in the biology of RORγT agonists and their potential application in anticancer therapy.

Interleukins (Cytokines) as Biomarkers in Colorectal Cancer: Progression, Detection, and Monitoring

Cancer is the primary cause of death in economically developed countries and the second leading cause in developing countries. Colorectal cancer (CRC) is the third most common cause of cancer-related deaths worldwide. Risk factors for CRC include obesity, a diet low in fruits and vegetables, physical inactivity, and smoking. CRC has a poor prognosis, and there is a critical need for new diagnostic and prognostic biomarkers to reduce related deaths. Recently, studies have focused more on molecular testing to guide targeted treatments for CRC patients. The most crucial feature of activated immune cells is the production and release of growth factors and cytokines that modulate the inflammatory conditions in tumor tissues. The cytokine network is valuable for the prognosis and pathogenesis of colorectal cancer as they can aid in the cost-effective and non-invasive detection of cancer. A large number of interleukins (IL) released by the immune system at various stages of CRC can act as "biomarkers". They play diverse functions in colorectal cancer, and include IL-4, IL-6, IL-8, IL-11, IL-17A, IL-22, IL-23, IL-33, TNF, TGF-β, and vascular endothelial growth factor (VEGF), which are pro-tumorigenic genes. However, there are an inadequate number of studies in this area considering its correlation with cytokine profiles that are clinically useful in diagnosing cancer. A better understanding of cytokine levels to establish diagnostic pathways entails an understanding of cytokine interactions and the regulation of their various biochemical signaling pathways in healthy individuals. This review provides a comprehensive summary of some interleukins as immunological biomarkers of CRC.

Endothelial cells-directed angiogenesis in colorectal cancer: Interleukin as the mediator and pharmacological target

Enhanced angiogenesis is a cancer hallmark and critical for colorectal cancer (CRC) invasion and metastasis. Upon exposure to proangiogenic factors, therefore, targeting tumor-associated proangiogenic factors/receptors hold great promise as a therapeutic modality to treat CRC, particularly metastatic CRC. Accumulating evidence from numerous studies suggests that tumor endothelial cells (ECs) are not only the target of proangiogenic factors, but also function as the cellular source of proangiogenic factors. Studies showed that ECs can produce different proangiogenic factors to participate in the regulation of angiogenesis process, in which ECs-derived interleukins (ILs) show a potential stimulatory effect on angiogenesis via either an direct action on their receptors expressed on progenitor of ECs or an indirect way through enhanced production of other proangiogenic factors. Although a great deal of attention is given to the effects of tumor-derived and immune cell-derived ILs, few studies describe the potential effects of vascular ECs-derived ILs on the tumor angiogenesis process. This review provides an updated summary of available information on proangiogenic ILs, such as IL-1, IL-6, IL-8, IL-17, IL-22, IL-33, IL-34, and IL-37, released by microvascular ECs as potential drivers of the tumor angiogenesis process and discusses their potential as a novel candidate for antiangiogenic target for the treatment of CRC patients.

Cytokine-mediated crosstalk between cancer stem cells and their inflammatory niche from the colorectal precancerous adenoma stage to the cancerous stage: Mechanisms and clinical implications

The majority of colorectal cancers (CRCs) are thought to arise from precancerous adenomas. Upon exposure to diverse microenvironmental factors, precancerous stem cells (pCSCs) undergo complex genetic/molecular changes and gradually progress to form cancer stem cells (CSCs). Accumulative evidence suggests that the pCSC/CSC niche is an inflammatory dominated milieu that contains different cytokines that function as the key communicators between pCSCs/CSCs and their niche and have a decisive role in promoting CRC development, progression, and metastasis. In view of the importance and increasing data about cytokines in modulating pCSCs/CSC stemness properties and their significance in CRC, this review summarizes current new insights of cytokines, such as interleukin (IL)-4, IL-6, IL-8, IL-17A, IL-22, IL-23, IL-33 and interferon (IFN)-γ, involving in the modulation of pCSC/CSC properties and features in precancerous and cancerous lesions and discusses the possible mechanisms of adenoma progression to CRCs and their therapeutic potential.

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

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

Gut Microbiota and Tumor Immune Escape: A New Perspective for Improving Tumor Immunotherapy

The gut microbiota is a large symbiotic community of anaerobic and facultative aerobic bacteria inhabiting the human intestinal tract, and its activities significantly affect human health. Increasing evidence has suggested that the gut microbiome plays an important role in tumor-related immune regulation. In the tumor microenvironment (TME), the gut microbiome and its metabolites affect the differentiation and function of immune cells regulating the immune evasion of tumors. The gut microbiome can indirectly influence individual responses to various classical tumor immunotherapies, including immune checkpoint inhibitor therapy and adoptive immunotherapy. Microbial regulation through antibiotics, prebiotics, and fecal microbiota transplantation (FMT) optimize the composition of the gut microbiome, improving the efficacy of immunotherapy and bringing a new perspective and hope for tumor treatment.

Cytokine- and chemokine-induced inflammatory colorectal tumor microenvironment: Emerging avenue for targeted therapy

Colorectal cancer (CRC) is a predominant life-threatening cancer, with liver and peritoneal metastases as the primary causes of death. Intestinal inflammation, a known CRC risk factor, nurtures a local inflammatory environment enriched with tumor cells, endothelial cells, immune cells, cancer-associated fibroblasts, immunosuppressive cells, and secretory growth factors. The complex interactions of aberrantly expressed cytokines, chemokines, growth factors, and matrix-remodeling enzymes promote CRC pathogenesis and evoke systemic responses that affect disease outcomes. Mounting evidence suggests that these cytokines and chemokines play a role in the progression of CRC through immunosuppression and modulation of the tumor microenvironment, which is partly achieved by the recruitment of immunosuppressive cells. These cells impart features such as cancer stem cell-like properties, drug resistance, invasion, and formation of the premetastatic niche in distant organs, promoting metastasis and aggressive CRC growth. A deeper understanding of the cytokine- and chemokine-mediated signaling networks that link tumor progression and metastasis will provide insights into the mechanistic details of disease aggressiveness and facilitate the development of novel therapeutics for CRC. Here, we summarized the current knowledge of cytokine- and chemokine-mediated crosstalk in the inflammatory tumor microenvironment, which drives immunosuppression, resistance to therapeutics, and metastasis during CRC progression. We also outlined the potential of this crosstalk as a novel therapeutic target for CRC. The major cytokine/chemokine pathways involved in cancer immunotherapy are also discussed in this review.

The presentation and regulation of the IL-8 network in the epithelial cancer stem-like cell niche in patients with colorectal cancer

BACKGROUND

Accumulative evidence suggests that the biological behavior of cancer stem-like cells (CSCs) is regulated by their surrounding niche, in which cytokines function as one of the main mediators for the interaction between CSCs and their microenvironment in the colorectal cancer (CRC).

METHODS

We characterized the presentation of CSCs and the interleukin (IL)- 8 network in the adenoma/CRC epithelium using quantitative real-time PCR (q-PCR), immunohistochemistry (IHC) and double immunofluorescence. In addition, the capacity of IL-1β to stimulate epithelial IL-8 production in colon cancer Caco-2 cells was examined in vitro and the IL-8 product was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

IHC observation showed increased expression of both CSCs and IL-8 in the adenoma and CRC epithelium, and q-PCR results revealed that increased expression of IL-1β transcript was strongly correlated with increased IL-8 transcript levels in both adenoma and CRC tissues. Double immunofluorescence images demonstrated the coexpression of the IL-8 receptors IL-8RA and IL-8RB with LGR5 labeled CSCs in CRC tissue sections. Consistently, in vitro experiments showed that coculture of Caco-2 cells with IL-1β at concentrations of 1, 5, 10 and 20 ng/ml resulted in a dose-dependent release of IL-8, which could be specifically inhibited by cotreatment with the IL-1β receptor antagonist.

CONCLUSIONS

These results demonstrate activation of the IL-8 network in the niche of CSCs from the precancerous adenoma stage to the CRC stage, which is potentially stimulated by IL-1β in CRC cells.

Innate lymphoid cells in colorectal cancer

Innate lymphoid cells (ILC) can be viewed as the innate counterparts of T cells. In contrast to T cells, ILCs exert their functions in antigen‐independent manners, relying on tissue‐derived signals from other immune cells, stroma and neurons. Natural killer (NK) cells have been known for their antitumour effects for decades. However, the roles of other ILC subtypes in cancer immunity are just now starting to be unravelled. ILCs contribute to both homeostasis and inflammation in the intestinal mucosa. Intestinal inflammation predisposes the intestine for the development of colonic dysplasia and colorectal cancer (CRC). Recent data from mouse models and human studies indicate that ILCs play a role in CRC, exerting both protumoural and antitumoural functions. Studies also suggest that intratumoural ILC frequencies and expression of ILC signature genes can predict disease progression and response to PD‐1 checkpoint therapy in CRC. In this mini‐review, we focus on such recent insights and their implications for understanding the immunobiology of CRC. We also identify knowledge gaps and research areas that require further work.

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.

Adenoma to carcinoma: A portrait of molecular and immunological profiles of colorectal sporadic tumors

An in-depth investigation of the molecular and immunologic properties of colorectal adenoma is important for understanding the mechanisms of colorectal cancer (CRC) initiation and development through the adenoma pathway. We performed a meta-analysis of the gene expression data from seven CRC and colorectal sporadic conventional adenoma datasets. We compared the enrichment levels of immune signatures between adenoma, normal colon, and CRC, then applied immunohistochemistry to compare the CD3 + and CD8 + T cells infiltration using samples of adenoma, contiguous adenoma, and CRC. We identified differentially expressed genes (DEGs) between adenoma, normal colon, and CRC, then performed pathway, network, immune correlation, and survival analyses on the DEGs. Adenoma had lower enrichment levels of antitumor immune signatures (CD8 + T cells, NK cells, and MHC Class I) while higher levels of TGF-β and Th17 signatures. Immunohistochemistry revealed variations in CD3 + and CD8 + T cells infiltration between low-grade and high-grade adenomas and between adenoma, normal colon, and CRC. We identified two groups of genes, which we named (NACupGs and NACdownGs), with consistent expression elevation and reduction respectively across the normal, precancerous, and cancerous stages. 48% of the NACupGs had expression levels highly correlated with Treg and TGF-β immune signatures, of which 39% were inversely correlated with CRC survival. We conclude that anti-tumor immune response is reduced at the precancerous (adenoma) stage which is characterized by prominent TGF-β and Th17 activity. The alterations of molecular and immunological profiles in adenoma can provide new insights into the initiation and development of CRC.

Immune Responses Vary in Preinvasive Colorectal Lesions by Tumor Location and Histology

Immune responses vary in colorectal cancers, which strongly influence prognosis. However, little is known about the variance in immune response within preinvasive lesions. The study aims to investigate how the immune contexture differs by clinicopathologic features (location, histology, dysplasia) associated with progression and recurrence in early carcinogenesis. We performed a cross-sectional study using preinvasive lesions from the surgical pathology laboratory at the Medical University of South Carolina. We stained the tissues with immunofluorescence antibodies, then scanned and analyzed expression using automated image analysis software. We stained CD117 as a marker of mast cells, CD4/RORC to indicate Th17 cells, MICA/B as a marker of NK-cell ligands, and also used antibodies directed against cytokines IL6, IL17A, and IFNγ. We used negative binomial regression analysis to compare analyte density counts by location, histology, degree of dysplasia adjusted for age, sex, race, and batch. All immune markers studied (except IL17a) had significantly higher density counts in the proximal colon than distal colon and rectum. Increases in villous histology were associated with significant decreases in immune responses for IL6, IL17a, NK ligand, and mast cells. No differences were observed in lesions with low- and high-grade dysplasia, except in mast cells. The lesions of the proximal colon were rich in immune infiltrate, paralleling the responses observed in normal mucosa and invasive disease. The diminishing immune response with increasing villous histology suggests an immunologically suppressive tumor environment. Our findings highlight the heterogeneity of the immune responses in preinvasive lesions, which may have implications for prevention strategies. PREVENTION RELEVANCE: Our study is focused on immune infiltrate expression in preinvasive colorectal lesions; our results suggest important differences by clinicopathologic features that have implications for immune prevention research.

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.

Dynamic stromal cellular reaction throughout human colorectal adenoma-carcinoma sequence: A role of TH17/IL-17A

BACKGROUND

Accumulating data suggest that the tumour stroma rapidly undergoes dynamic mechanical and cellular changes by which creates a supportive milieu to promote disease progression and metastasis. Cytokines are reported to play a key role in the modulation of tumour stromal response.

METHODS

The activation of TH17/interleukin (IL)-17A network in association with tumour stromal proliferative and cellular response in samples from 50 patients with colorectal adenoma, 45 with colorectal cancer (CRCs) were elucidated with quantitative real-time PCR (q-PCR), immunohistochemistry and double immunofluorescence.

RESULTS

q-PCR results showed that retinoic acid-receptor-related orphan receptor-C, a critical transcriptional factor for TH17 cell differentiation, was significantly increased at the adenoma stage and slightly decreased at the CRC stage, but was still higher than that at normal controls. The level of TH17 signature cytokine IL-17A was shown in an increasing gradient throughout the adenoma-carcinoma sequence. Immunohistochemistry revealed an activated proliferative rate evaluated by Ki67 and population expansion of myofibroblasts in the adenoma/CRC stroma. Notably, densities of IL-17A-expressing cells were associated with populations of Ki67-positive cells and myofibroblasts in the adenoma/CRC stroma. Finally, CD146-positive stromal cells are an important participator for stroma remodelling, double immunofluorescence image demonstrated that IL-17 receptor C, one of the key elements for IL-17 receptor complex, was highly expressed in CD146-positive adenoma/CRC stromal cells.

CONCLUSIONS

An activated TH17/IL-17A network in the tumour microenvironment is significantly associated with dynamic stromal cellular response throughout the adenoma-carcinoma sequence, which might provide a supportive environment for the initiation and progression of CRC.

Preinvasive Colorectal Lesions of African Americans Display an Immunosuppressive Signature Compared to Caucasian Americans

BACKGROUND

African Americans (AAs) have higher colorectal cancer (CRC) incidence and mortality rate than Caucasian Americans (CAs). Recent studies suggest that immune responses within CRCs contribute to the disparities. If racially distinct immune signatures are present in the early phases of carcinogenesis, they could be used to develop interventions to prevent or slow disease.

METHODS

We selected a convenience sample of 95 patients (48 CAs, 47 AAs) with preinvasive colorectal adenomas from the surgical pathology laboratory at the Medical University of South Carolina. Using immunofluorescent-conjugated antibodies on tissue slides from the lesions, we quantified specific immune cell populations: mast cells (CD117+), Th17 cells (CD4+RORC+), and NK cell ligand (MICA/B) and inflammatory cytokines, including IL-6, IL-17A, and IFN-γ. We compared the mean density counts (MDCs) and density rate ratios (RR) and 95% CI of immune markers between AAs to CAs using negative binomial regression analysis. We adjusted our models for age, sex, clinicopathologic characteristics (histology, location, dysplasia), and batch.

RESULTS

We observed no racial differences in age or sex at the baseline endoscopic exam. AAs compared to CAs had a higher prevalence of proximal adenomas (66% vs. 40%) and a lower prevalence of rectal adenomas (11% vs. 23%) (p =0.04) but no other differences in pathologic characteristics. In age, sex, and batch adjusted models, AAs vs. CAs had lower RRs for cells labeled with IFNγ (RR 0.50 (95% CI 0.32-0.81); p=0.004) and NK cell ligand (RR 0.67 (0.43-1.04); p=0.07). In models adjusted for age, sex, and clinicopathologic variables, AAs had reduced RRs relative to CAs for CD4 (p=0.02), NK cell ligands (p=0.01), Th17 (p=0.005), mast cells (p=0.04) and IFN-γ (p< 0.0001).

CONCLUSIONS

Overall, the lower RRs in AAs vs. CAs suggests reduced effector response capacity and an immunosuppressive ('cold') tumor environment. Our results also highlight the importance of colonic location of adenoma in influencing these differences; the reduced immune responses in AAs relative to CAs may indicate impaired immune surveillance in early carcinogenesis. Future studies are needed to understand the role of risk factors (such as obesity) in influencing differences in immune responses by race.

The Mechanisms Leading to Distinct Responses to PD-1/PD-L1 Blockades in Colorectal Cancers With Different MSI Statuses

Current clinical studies showed distinct therapeutic outcomes, in which CRC patients with mismatch repair-deficient (dMMR)/microsatellite instability high (MSI-H) seem to be relatively more "sensitive" in response to anti-programmed death-1 receptor (PD-1)/programmed death-1 receptor ligand 1 (PD-L1) therapy than those with mismatch repair-proficient (pMMR)/microsatellite instability-low (MSI-L). The mechanisms by which the same PD-1/PD-L1 blockades lead to two distinct therapeutic responses in CRC patients with different MSI statuses remain poorly understood and become a topic of great interest in both basic research and clinical practice. In this review of the potential mechanisms for the distinct response to PD-1/PD-L1 blockades between dMMR/MSI-H CRCs and pMMR/MSI-L CRCs, relevant references were electronically searched and collected from databases PubMed, MEDLINE, and Google scholar. Sixty-eight articles with full text and 10 articles by reference-cross search were included for final analysis after eligibility selection according to the guidelines of PRISMA. Analysis revealed that multiple factors e.g. tumor mutation burden, immune cell densities and types in the tumor microenvironment, expression levels of PD-1/PD-L1 and cytokines are potential determinants of such distinct response to PD-1/PD-L1 blockades in CRC patients with different MSI statuses which might help clinicians to select candidates for anti-PD-1/PD-L1 therapy and improve therapeutic response in patients with CRC.

Targeting the interleukin-17 immune axis for cancer immunotherapy

IL-17 plays versatile roles during tumorigenesis. Here, Vitiello and Miller summarize current knowledge in harnessing IL-17–producing γδ and Th17 cells for successful cancer immunotherapy.

The role of IL-17 in cancer remains controversial. Emerging evidence suggests that during early oncogenesis IL-17 supports tumor growth, whereas in established tumors IL-17 production by γδ and Th17 cells potentiates antitumor immunity. Consequently, γδ and Th17 cells are attractive targets for immunotherapy in the IL-17 immune axis. To optimize IL-17–based immunotherapy, a deeper understanding of the cytokines dictating IL-17 production and the polarity of γδ and Th17 cells is critical. Here, we delve into the dichotomous roles of IL-17 in cancer and provide insight into the tumor microenvironment conducive for successful IL-17–based γδ and Th17 cell immunotherapy.

Loss of Interleukin-17RA Expression is Associated with Tumour Progression in Colorectal Carcinoma

Interleukin-17 (IL-17) is a pro-inflammatory cytokine found in various cancers. Current evidence indicates that IL-17 plays a vital role in tumour initiation and progression in colorectal carcinoma (CRC) via binding with its receptor, IL-17RA. However, the association between clinicopathological features and presence of IL-17 and IL-17RA protein in primary CRC tissues remains unclear. This study also investigates the difference between the presence of IL-17 and IL-17RA in the paired tumour tissues versus adjacent normal tissues. The presence of IL-17RA and IL-17 protein in primary CRC tissues was determined by immunohistochemistry. Associations between clinicopathological features and IL-17RA and IL-17 immunoreactivity, were analyzed by χ2 tests. We found that both IL-17RA (p = 0.001) and IL-17 (p = 0.025) in tumour cells of primary CRC tissues was significantly lower as compared to adjacent normal tissue. Positive immunoreactivity for IL-17RA and IL-17 were detected in 51.0% and 16.8% of tumour tissues, respectively. Furthermore, negative immunoreactivity of IL-17R was significantly associated with advanced stage according to TNM classifier (p = 0.027), high grade of tumour (p = 0.019), increased depth of tumour invasion (p = 0.023) and vascular invasion (p = 0.039). Positive IL-17 immunoreactivity was associated with advanced stage (p = 0.008) and lymph node metastasis (p = 0.008). Thus, this study suggests that the loss of IL-17RA expression occurs as tumour progresses and this may predict the aggressiveness of tumour whilst expression of IL-17 promotes tumour progression and lymph node metastasis. Thus, loss of IL-17RA could be a useful prognostic biomarker for tumour progression in CRC patients.

Cytokines regulate the antigen-presenting characteristics of human circulating and tissue-resident intestinal ILCs

ILCs and T helper cells have been shown to exert bi-directional regulation in mice. However, how crosstalk between ILCs and CD4⁺ T cells influences immune function in humans is unknown. Here we show that human intestinal ILCs co-localize with T cells in healthy and colorectal cancer tissue and display elevated HLA-DR expression in tumor and tumor-adjacent areas. Although mostly lacking co-stimulatory molecules ex vivo, intestinal and peripheral blood (PB) ILCs acquire antigen-presenting characteristics triggered by inflammasome-associated cytokines IL-1β and IL-18. IL-1β drives the expression of HLA-DR and co-stimulatory molecules on PB ILCs in an NF-κB-dependent manner, priming them as efficient inducers of cytomegalovirus-specific memory CD4⁺ T-cell responses. This effect is strongly inhibited by the anti-inflammatory cytokine TGF-β. Our results suggest that circulating and tissue-resident ILCs have the intrinsic capacity to respond to the immediate cytokine milieu and regulate local CD4⁺ T-cell responses, with potential implications for anti-tumor immunity and inflammation.

Murine ILCs can modulate T cell responses in MHCII-dependent manner. Here the authors show that human ILCs process and present antigens and induce T-cell responses upon exposure to IL-1-family cytokines; along with the article by Lehmann et al, this work elucidates how cytokines set context specificity of ILC-T cell crosstalk by regulating ILC antigen presentation.

ST2 and regulatory T cells in the colorectal adenoma/carcinoma microenvironment: implications for diseases progression and prognosis

ST2 (also known as IL1RL1) is the critical functional receptor for interleukin (IL)-33 in stimulating regulatory T cell (Treg) expansion and function in physiological and pathological conditions. We examined the correlation between ST2 cell expression and FoxP3 positive Tregs in both colorectal adenoma and cancer (CRC) microenvironment by real-time PCR, immunohistochemistry (IHC) and double immunofluorescences. The clinicopathological and prognostic significance of cellular ST2-positive cells and FoxP3-positive Tregs in patients with adenoma and CRC were evaluated. Real-time PCR results revealed increased expression levels of ST2 and FoxP3 mRNAs in both adenoma and CRC tissues as compared with control tissues. IHC analysis confirmed increased densities of ST2-positive cells in both the adenoma/CRC epithelium and stroma, which show a close positive linear association with the densities of FoxP3-positive Tregs in respective compartments. Pathological feature analysis showed that densities of ST2-positive cells in the tumor stroma were notably associated with degree of dysplastic grading in patients with adenoma, and disease stages and lymph node metastasis in patients with CRC. Kaplan-Meier survival curves suggested that CRC patients with high densities of ST2-positive cells in the stroma tend to have a shorter overall survival. We therefore concluded that increased densities of ST2-postive cells relate to Treg accumulation within the adenoma/CRC microenvironment, suggesting the IL-33/ST2 pathway as a potential contributor for immunosuppressive milieu formation that impact disease stage and prognosis in patients with CRC.

Molecular Aspects of Colorectal Adenomas: The Interplay among Microenvironment, Oxidative Stress, and Predisposition

The development of colorectal cancer (CRC) is a multistep process initiated by a benign polyp that has the potential to evolve into in situ carcinoma through the interactions between environmental and genetic factors. CRC incidence rates are constantly increased for young adult patients presenting an advanced tumor stage. The majority of CRCs arise from colonic adenomas originating from aberrant cell proliferation of colon epithelium. Endoscopic polypectomy represents a tool for early detection and removal of polyps, although the occurrence of cancers after negative colonoscopy shows a significant incidence. It has long been recognized that the aberrant regulation of Wingless/It (Wnt)/β-Catenin signaling in the pathogenesis of colorectal cancer is supported by its critical role in the differentiation of stem cells in intestinal crypts and in the maintenance of intestinal homeostasis. For this review, we will focus on the development of adenomatous polyps through the interplay between renewal signaling in the colon epithelium and reactive oxygen species (ROS) production. The current knowledge of molecular pathology allows us to deepen the relationships between oxidative stress and other risk factors as lifestyle, microbiota, and predisposition. We underline that the chronic inflammation and ROS production in the colon epithelium can impair the Wnt/β-catenin and/or base excision repair (BER) pathways and predispose to polyp development. In fact, the coexistence of oxidative DNA damage and errors in DNA polymerase can foster C>T transitions in various types of cancer and adenomas, leading to a hypermutated phenotype of tumor cells. Moreover, the function of Adenomatous Polyposis Coli (APC) protein in regulating DNA repair is very important as therapeutic implication making DNA damaging chemotherapeutic agents more effective in CRC cells that tend to accumulate mutations. Additional studies will determine whether approaches based on Wnt inhibition would provide long-term therapeutic value in CRC, but it is clear that APC disruption plays a central role in driving and maintaining tumorigenesis.

TH9, TH17, and TH22 Cell Subsets and Their Main Cytokine Products in the Pathogenesis of Colorectal Cancer

In recent years, several newly identified T helper (T_H) cell subsets, such as T_H9, T_H17, and T_H22 cells, and their respective cytokine products, IL-9, IL-17, and IL-22, have been reported to play critical roles in the development of chronic inflammation in the colorectum. Since chronic inflammation is a potent driving force for the development of human colorectal cancer (CRC), the contributions of T_H9/IL-9, T_H17/IL-17, and T_H22/IL-22 in the pathogenesis of CRC have recently become an increasingly popular area of scientific investigation. Extensive laboratory and clinical evidence suggests a positive relationship between these new T_H subsets and the growth and formation of CRC, whereas, administration of IL-9, IL-17, and IL-22 signaling inhibitors can significantly alter the formation of colorectal chronic inflammation or CRC lesions in animal models, suggesting that blocking these cytokine signals might represent promising immunotherapeutic strategies. This review summarizes recent findings and currently available data for understanding the vital role and therapeutic significance of T_H9/IL-9, T_H17/IL-17, and T_H22/IL-22 in the development of colorectal tumorigenesis.

Interleukin-17A polymorphisms predict the response and development of tolerance to FOLFOX chemotherapy in colorectal cancer treatment

Polymorphic variants in IL-17A gene were differentially associated with colorectal cancer (CRC) susceptibility but their link with response and toxicity to CRC treatment have not yet been evaluated. We investigated association between seven IL-17A variants with the response and toxicity to CRC treatment in 294 patients with CRC. IL-17A genotyping was done by real-time PCR. MAF of rs3748067 was significantly higher in CRC cases resistant to FOLFOX treatment (R+) than non resistant (R-). Significantly higher rs3804513 MAF was noted in R+ versus R- colon cancer (CC). Higher rs2275913 and rs10484879, and reduced rs3804513 MAF were seen in rectal cancer (RC) tolerant to FOLFOX (T+) compared to (T-) patients. Strong association of rs3819025, rs3804513, and rs7747909 was found with tolerance to RC treatment. rs3748067 was associated with FOLFOX tolerance in CC but not RC. Significant higher frequency of AGGCAGG and GAGCAGG haplotypes was seen among R + CC, thus assigning non-favorable nature to these haplotypes. Higher and lower frequencies of GAGTAAG and AGGCTGA haplotypes, respectively, were observed in T + RC, thereby assigning FOLFOX-tolerant and non-tolerant nature to these haplotypes. The obtained results suggest that IL-17A variants and haplotypes may be a target for future management of CRC treatment.

Human Gut-Associated Natural Killer Cells in Health and Disease

It is well established that natural killer (NK) cells are involved in both innate and adaptive immunity. Indeed, they can recognize molecules induced at the cell surface by stress signals and virus infections. The functions of NK cells in the gut are much more complex. Gut NK cells are not precisely organized in lymphoid aggregates but rather scattered in the epithelium or in the stroma, where they come in contact with a multitude of antigens derived from commensal or pathogenic microorganisms in addition to components of microbiota. Furthermore, NK cells in the bowel interact with several cell types, including epithelial cells, fibroblasts, macrophages, dendritic cells, and T lymphocytes, and contribute to the maintenance of immune homeostasis and development of efficient immune responses. NK cells have a key role in the response to intestinal bacterial infections, primarily through production of IFNγ, which can stimulate recruitment of additional NK cells from peripheral blood leading to amplification of the anti-bacterial immune response. Additionally, NK cells can have a role in the pathogenesis of gut autoimmune inflammatory bowel diseases (IBDs), such as Crohn's Disease and Ulcerative Colitis. These diseases are considered relevant to the generation of gastrointestinal malignancies. Indeed, the role of gut-associated NK cells in the immune response to bowel cancers is known. Thus, in the gut immune system, NK cells play a dual role, participating in both physiological and pathogenic processes. In this review, we will analyze the known functions of NK cells in the gut mucosa both in health and disease, focusing on the cross-talk among bowel microenvironment, epithelial barrier integrity, microbiota, and NK cells.

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.

Innate Lymphoid Cells in Colorectal Cancers: A Double-Edged Sword

The immune system plays a fundamental role at mucosal barriers in maintaining tissue homeostasis. This is particularly true for the gut where cells are flooded with microbial-derived signals and antigens, which constantly challenge the integrity of the intestinal barrier. Multiple immune cell populations equipped with both pro- and anti-inflammatory functions reside in the gut tissue and these cells tightly regulate intestinal health and functions. Dysregulation of this finely tuned system can progressively lead to autoimmune disease and inflammation-driven carcinogenesis. Over the last decade, the contribution of the adaptive immune system in controlling colorectal cancer has been studied in detail, but the role of the innate system, particularly innate lymphoid cells (ILCs), have been largely overlooked. By sensing their microenvironment, ILCs are essential in supporting gut epithelium repair and controling bacterial- and helminth-mediated intestinal infections, highlighting their important role in maintaining tissue integrity. Accumulating evidence also suggests that they may play an important role in carcinogenesis including intestinal cancers. In this review, we will explore the current knowledge about the pro- and anti-tumor functions of ILCs in colorectal cancer.

Roles for Interleukin 17 and Adaptive Immunity in Pathogenesis of Colorectal Cancer

Sporadic colorectal cancer is one of the most common and lethal cancers worldwide. The locations and functions of immune cells in the colorectal tumor microenvironment are complex and heterogeneous. T-helper (Th)1 cell-mediated responses against established colorectal tumors are associated with better outcomes of patients (time of relapse-free or overall survival), whereas Th17 cell-mediated responses and production of interleukin 17A (IL17A) have been associated with worse outcomes of patients. Tumors that develop in mouse models of colorectal cancer are rarely invasive and differ in many ways from human colorectal tumors. However, these mice have been used to study the mechanisms by which Th17 cells and IL17A promote colorectal tumor initiation and growth, which appear to involve their direct effects on colon epithelial cells. Specific members of the colonic microbiota may promote IL17A production and IL17A-producing cell functions in the colonic mucosa to promote carcinogenesis. Increasing our understanding of the interactions between the colonic microbiota and the mucosal immune response, the roles of Th17 cells and IL17 in these interactions, and how these processes are altered during colon carcinogenesis, could lead to new strategies for preventing or treating colorectal cancer.

Contribution of IL-33 to the Pathogenesis of Colorectal Cancer

The development of colorectal cancer (CRC) is not only determined by transformed cells per se, but also by factors existing in their immune microenvironment. Accumulating scientific evidence has revealed that interleukin (IL)-33, an IL-1 family member, plays an essential role in the regulation of immune response and is relevant in CRC pathogenesis. Data from both human and experimental studies demonstrated that IL-33 inhibits host anti-tumor immunity, remodels tumor stroma and enhances angiogenesis, thereby promoting the development of CRC. These pro-tumor effects of IL-33 are mainly mediated by IL-33 receptor ST2 (also known as IL-1RL1). Based on those findings, it is currently hypothesized that the IL-33/ST2 pathway is a potential biomarker and therapeutic target for colorectal tumorigenesis. Herein, we summarize the recent discoveries in understanding the critical role of the IL-33/ST2 pathway in contributing to the pathogenesis of colorectal tumorigenesis and discuss its potential implications for the future development of effective anti-tumor strategies.

IL-1β/IL-6 network in the tumor microenvironment of human colorectal cancer

OBJECTIVES

Recent studies suggest that the interaction between interleukin (IL)-1β and IL-6 in the microenvironment might be involved in the development and progression of human colorectal cancer (CRC). However, the expression of IL-1β/IL-6 network within the CRC microenvironment is not fully understood.

MATERIALS AND METHODS

The level of IL-1β/IL-6 network expression in 40 biopsies of sporadic CRC and 15 biopsies of controls was assessed using quantitative real-time polymerase chain reaction (PCR) assay, immunohistochemistry (IHC) and double immunofluorescence staining.

RESULTS

Quantitative results obtained by real-time PCR revealed that both IL-1β and IL-6 mRNA expressions were increased in CRC tissues compared with expressions in controls. In which, IL-6 mRNA expression in primary CRC tissues showed a statistically significant relationship with tumor invasion depth. IHC observations confirmed that increased expression of IL-1β and IL-6 immunoreactivities was located in both the CRC epithelium and stroma. Furthermore, IHC results also revealed that increased expression of IL-1β receptor type 1 (IL-1R1) and IL-6 receptor (IL-6R) were observed in both CRC epithelial and stromal cells. IHCs in serial CRC sections and double immunofluorescence staining revealed a highly co-expression of IL-1R1 immunoreactivity with IL-6 immunoreactivity in the same cells, which confirmed a histological fundament of IL-1β/IL-6 network.

CONCLUSION

The IL-1β/IL-6 network is highly expressed in the CRC microenvironment, indicating that this network is important in the progression of CRC.

Temporal and spatial changes of cells positive for stem-like markers in different compartments and stages of human colorectal adenoma-carcinoma sequence

Considerable evidence supports the idea that stem-like cells may play an essential role during the development of colorectal cancer (CRC). To accomplish this aim, we use immunohistochemistry (IHC) and double IHC with different potential stem-like markers, anti-musashi (Msi), anti-CD133, anti- LGR5 and anti-ALDH1 to examine the presentation of stem-like cells in different compartments including adenoma/CRC epithelium, transitional crypts and tumor stroma in colorectal adenoma and CRC. The results showed that cells positive for stem-like markers were remarkably increased in number and frequently observed in the adenoma/CRC epithelium, transitional crypts and tumor stroma. Notably, the population of cells positive for stem-liker markers was expanded from the base to the middle part of the transitional crypt in both adenoma and CRC tissues, reflecting that stem-like cells are likely involved in the process of colorectal tumorigenesis. Counting results showed that the grading scores of cells positive for LGR5 and ALDH1 in the adenoma/CRC epithelium were significantly increased relative with the control epithelium, and associated with the degree of dysplasia in the adenoma and node involvement in the CRC (all P < 0.05). In addition, the density of cells positive for stem-like markers in the adenomatous/cancerous stroma was also increased and paralleled an increase in the density of proliferative stromal cells labeled by PCNA, which were primarily identified as vimentin positive fibroblasts. Our results have revealed a changed temporal and spatial presentation of stem-like markers in different stages of human colorectal adenoma-carcinoma sequence, which might be a hallmark of the adenoma-carcinoma transition.

Expression and location of IL-17A, E, F and their receptors in colorectal adenocarcinoma: Comparison with benign intestinal disease

The research aimed to investigate secretion, expression and location of IL-17 relative ligands, IL-17 relative receptors, infiltrating inflammatory cells and parenchymal structural cells in colorectal cancer (CRC) compared with ulcerative colitis (UC) and benign hyperplastic polyp. 29 human intestinal tissues with CRC, 17 with UC and 7 with polyp were stained using immunohistochemistry to evaluate immunoreactivity for IL-17 family relative ligands including IL-17A, E, F and their respective relative receptors such as IL-17RA, IL-17RB and IL-17RC. At the same time the infiltration of inflammatory cells including lymphocytes, phagocytes, mast cells and neutrophils and parenchymal structural cell changes involving vascular endothelial cells and CD90⁺ fibroblast cells were also evaluated using the same methods The immunoreactivity or positive inflammatory cells of all the sections were analyzed using professional image analysis software to determine statistical significance. The immunoreactivity for IL-17A, IL-17RA, IL-17E, IL-17RB and IL-17F showed significant decrease in CRC tissue when compared to UC (p = 0.00001. respectively). The reduction of above IL-17 relative ligands and receptors was accompanied by an obvious decrease in the number of infiltrating neutrophils and mast cells in CRC (p = 0.00001 and p = 0.007, respectively) but accompanied by a marked increase of CD31⁺ blood vessels (p = 0.001). The immunoreactivity of IL-17A, IL-17RA, IL-17E, IL-17RB and IL-17F and the numbers of infiltrating neutrophils and mast cells showed significant decrease in CRC tissues when compared to those in polyp (p < 0.05). In contrast, the immunoreactivity of IL-17RC and the numbers of CD3⁺ 1ymphocytes were elevated in CRC when compared with those in polyp (p = 0.0001, p = 0.007, respectively). In CRC tissues, positive correlations between IL-17A, IL-17RA with CD68⁺ macrophages were observed respectively (r = 0.621, p = 0.0001; r = 0.75, p = 0.0001). IL-17 cytokine family including ligands and their corresponding receptors were secreted and expressed by infiltrating inflammatory cells. Not only infiltrating lymphocytes but also increased blood endothelial cells were relative significantly to genesis and progression of CRC.

Interleukin-34 sustains pro-tumorigenic signals in colon cancer tissue

Interleukin-34 (IL-34), a cytokine produced by a wide range of cells, binds to the macrophage colony-stimulating factor receptor (M-CSFR-1) and receptor-type protein-tyrosine phosphatase zeta (PTP-z) and controls myeloid cell differentiation, proliferation and survival. various types of cancers over-express IL-34 but the role of the cytokine in colorectal cancer (CRC) remains unknown. We here investigated the expression and functional role of IL-34 in CRC. A more pronounced expression of IL-34 was seen in CRC samples as compared to matched normal/benign colonic samples and this occurred at both RNA and protein level. Immunohistochemical analysis of CRC tissue samples showed that both cancer cells and lamina propria mononuclear cells over-expressed IL-34. Additionally, CRC cells expressed both M-CSFR-1 and PTP-z, thus suggesting that CRC cells can be responsive to IL-34. Indeed, stimulation of DLD-1 cancer cells with IL-34, but not with MSCF1, enhanced the cell proliferation and cell invasion without affecting cell survival. Analysis of intracellular signals underlying the mitogenic effect of IL-34 revealed that the cytokine enhanced activation of ERK1/2 and pharmacologic inhibition of ERK1/2 abrogated IL-34-driven cell proliferation. Consistently, IL-34 knockdown in HT-29 cells with a specific IL-34 antisense oligonucleotide reduced ERK1/2 activation, cell proliferation and enhanced the susceptibility of cells to Oxaliplatin-induced death. This is the first study showing up-regulation of IL-34 in CRC and suggesting a role for this cytokine in colon tumorigenesis.

A possible association of baseline serum IL-17A concentrations with progression-free survival of metastatic colorectal cancer patients treated with a bevacizumab-based regimen

BACKGROUND

Colorectal cancer is a major public health issue worldwide. Interleukin-17 (IL-17) and Th17 (T-helper cell type 17)-related molecules are involved in tumor development and in resistance to bevacizumab, an anti-vascular endothelial growth factor monoclonal antibody used in association with chemotherapy in metastatic colorectal cancer. Some studies have previously shown that IL-17A and IL-17F polymorphisms, respectively rs2275913 and rs763780, are associated with gastric or colorectal cancer risk. Here we aimed at studying the influence of IL-17A-related individual factors on overall survival and progression-free survival in patients with metastatic colorectal cancer treated with a bevacizumab-based chemotherapy.

METHODS

Pre-treatment serum biomarkers were retrospectively evaluated in 122 metastatic colorectal cancer patients treated by bevacizumab in combination with chemotherapy at 2-weeks intervals in a prospective cohort study (NCT00489697). The polymorphisms of IL-17A and IL-17F were analyzed by polymerase chain reaction - restriction fragment length polymorphism. Serum concentrations of Th17-related cytokines were measured by MultiPlex. The impact of individual parameters on overall survival and progression-free survival was assessed using multivariate Cox models.

RESULTS

High baseline IL-17A serum concentrations were significantly associated with shorter progression-free survival [p = 0.043]. Other baseline serum Th17-related cytokines and polymorphisms of IL-17 were not associated with overall survival or progression-free survival.

CONCLUSIONS

In this ancillary study, baseline serum IL-17A concentration is the only Th17/IL-17 related factor that was significantly associated with the response of patients with metastatic colorectal cancer to bevacizumab. But this main significant result is highly dependent on one case which, if left out, weakens the data. Other clinical studies are required to confirm this association.

TRIAL REGISTRATION

NCT00489697 . June 20, 2007.

Targeting the Tumor Microenvironment: The Protumor Effects of IL-17 Related to Cancer Type

The inflammatory process contributes to immune tolerance as well as to tumor progression and metastasis. By releasing extracellular signals, cancerous cells constantly shape their surrounding microenvironment through their interactions with infiltrating immune cells, stromal cells and components of extracellular matrix. Recently, the pro-inflammatory interleukin 17 (IL-17)-producing T helper lymphocytes, the Th17 cells, and the IL-17/IL-17 receptor (IL-17R) axis gained special attention. The IL-17 family comprises at least six members, IL-17A, IL-17B, IL-17C, IL-17D, IL-17E (also called IL-25), and IL-17F. Secreted as disulfide-linked homo- or heterodimers, the IL-17 bind to the IL-17R, a type I cell surface receptor, of which there are five variants, IL-17RA to IL-17RE. This review focuses on the current advances identifying the promoting role of IL-17 in carcinogenesis, tumor metastasis and resistance to chemotherapy of diverse solid cancers. While underscoring the IL-17/IL-17R axis as promising immunotherapeutic target in the context of cancer managing, this knowledge calls upon further in vitro and in vivo studies that would allow the development and implementation of novel strategies to combat tumors.

Cytokine-Induced Modulation of Colorectal Cancer

The emergence of novel immunomodulatory cancer therapies over the last decade, above all immune checkpoint blockade, has significantly advanced tumor treatment. For colorectal cancer (CRC), a novel scoring system based on the immune cell infiltration in tumors has greatly improved disease prognostic evaluation and guidance to more specific therapy. These findings underline the relevance of tumor immunology in the future handling and therapeutic approach of malignant disease. Inflammation can either promote or suppress CRC pathogenesis and inflammatory mediators, mainly cytokines, critically determine the pro- or anti-tumorigenic signals within the tumor environment. Here, we review the current knowledge on the cytokines known to be critically involved in CRC development and illustrate their mechanisms of action. We also highlight similarities and differences between CRC patients and murine models of CRC and point out cytokines with an ambivalent role for intestinal cancer. We also identify some of the future challenges in the field that should be addressed for the development of more effective immunomodulatory therapies.

Overexpression of interleukins IL-17 and IL-8 with poor prognosis in colorectal cancer induces metastasis

Current evidences indicated that a group of soluble mediators called chemokines is involved in tumor growth and metastasis. The association of IL-8 with tumor cell migration was previously found, and its expression was related to angiogenesis, tumor progression, and metastasis in many kinds of carcinomas in human and animal models. Furthermore, it has been showed that IL-17 plays its role as either a proteome of tumor progression or antitumor indifferent cancer models. To investigate the messenger RNA (mRNA) expressions of IL-8 and IL-17 in patients with colorectal cancer (CRC) and non-tumor tissue, quantitative real-time PCR was used in the study. Our results showed that expression of IL-8 mRNA was significantly increased in tumor tissues (mean ± SD 3.84 ± 0.08) compared with adjacent normal mucosa (mean ± SD 1.17 ± 0.75, P = 0.001). Furthermore, a higher expression of IL-17 mRNA was found in tumor tissues (mean ± SD 2.73 ± 0.69) when compared with normal tissues (mean ± SD 1.06 ± 0.07, P = 0.001). Our findings indicated that advanced tumor-node-metastasis (TNM) stage (P = 0.024) and histological grade (poorly differentiated, P = 0.013) and distant metastasis (P = 0.001) were correlated with expression of IL-8. Moreover, high expression of IL-17 showed significant association with early stage CRC (TNM) (P = 0.038). In conclusion, the expression of IL-8 and IL-17 mRNAs was significantly increased in tumor tissues compared with adjacent normal tissues. We found that advanced TNM stage and histological grade and distant metastasis were correlated with expression of IL-8, while high expression of IL-17 showed significant association with early stage CRC (TNM) stage and overexpression of IL-8 may be associated with progression of CRC.