Mast cells promote small bowel cancer in a tumor stage-specific and cytokine-dependent manner

IL-33 signaling is dispensable for the IL-10-induced enhancement of mast cell responses during food allergy

Background

The IL-33/ST2 axis plays a pivotal role in the development of IgE-mediated mast cell (MC) responses during food allergy. We recently demonstrated that the pleiotropic cytokine, IL-10, not only exerts proinflammatory effects on IgE-mediated MC activation, but also promotes IL-33-induced MC responses. However, whether IL-33 is necessary for IL-10's proinflammatory effects has not been examined.

Methods

To therefore determine the role of the IL-33/ST2 axis in this pathway, we assessed the effects of IL-10 on IgE-mediated MC activation and food allergy development in wild-type (WT) and ST2-/- mice.

Results

IL-10 stimulation significantly enhanced IL-33 gene expression, ST2 receptor expression, cytokine production, mMCP-1 secretion, and proliferation in IgE and antigen-activated bone marrow-derived MCs (BMMCs) from WT mice. ST2-/- BMMCs exhibited reduced cytokine secretion in response to IgE-dependent activation. However, IL-10 enhanced cytokine production, mMCP-1 secretion, and proliferation in these cells as well. To further assess the role of IL-10, food allergy was induced in WT and ST2-/- mice subjected to antibody-mediated IL-10 depletion. IL-10-depleted WT mice exhibited a significant attenuation in MC-mediated responses to OVA challenge. While ST2-/- mice also exhibited a profound suppression of MC responses, IL-10 depletion had no additional effects. However, ST2-/-/IL-10-/- mice exhibited further decreases in OVA-IgE and antigen-specific MC activation compared to ST2-/- mice.

Conclusion

Our data demonstrates that IL-10 can enhance MC responses in both WT and ST2-/- mice, further corroborating its proinflammatory effects on MCs and suggesting that they are not regulated by IL-33 signaling.

Mast cells: key players in digestive system tumors and their interactions with immune cells

Mast cells (MCs) are critical components of both innate and adaptive immune processes. They play a significant role in protecting human health and in the pathophysiology of various illnesses, including allergies, cardiovascular diseases and autoimmune diseases. Recent studies in tumor-related research have demonstrated that mast cells exert a substantial influence on tumor cell behavior and the tumor microenvironment, exhibiting both pro- and anti-tumor effects. Specifically, mast cells not only secrete mediators related to pro-tumor function such as trypsin-like enzymes, chymotrypsin, vascular endothelial cell growth factor and histamine, but also mediators related to anti-tumor progression such as cystatin C and IL-17F. This dual role of mast cells renders them an under-recognized but very promising target for tumor immunotherapy. Digestive system tumors, characterized by high morbidity and associated mortality rates globally, are increasingly recognized as a significant healthcare burden. This paper examines the influence of mast cell-derived mediators on the development of tumors in the digestive system. It also explores the prognostic significance of mast cells in patients with various gastrointestinal cancers at different stages of the disease. Additionally, the article investigates the interactions between mast cells and immune cells, as well as the potential relationships among intratumoral bacteria, immune cells, and mast cell within digestive system microenvironment. The aim is to propose new strategies for the immunotherapy of digestive system tumors by targeting mast cells.

Studies of Structure-Activity Relationship of 2-(Pyrrolidin-1ylmethyl)-1H-pyrrole-Based ST2 Inhibitors and Their Inhibition of Mast Cells Activation

ST2 belongs to the interleukin 1 receptor family and is expressed in immune cells including certain CD4+ T cells and mast cells. Binding of ST2 with interleukin 33 (IL-33) induces downstream signaling that activates NF-κB pathway. Although the ST2/IL-33 axis exerts immune tolerance via expansion of regulator T cells, the same axis also activates a subset of immune cells to produce proinflammatory cytokines in host defense or in tissue repair. Here, we reported the development of ST2 inhibitors with improved inhibitory activities against ST2 and metabolic stability based on a previous lead, iST2-14e. Using the human mast cell line (LAD2), we showed that ST2 inhibitors mitigated ST2 upregulation and reduced IL-1β released through degranulation, demonstrating that small-molecule ST2 inhibitors effectively attenuated the ST2/IL-33 signaling in human mast cells. Further optimization of the compounds may lay the foundation for developing ST2 inhibitors for the treatment of mast cells mediated diseases.

IL-10 Neutralization Attenuates Mast Cell Responses in a Murine Model of Experimental Food Allergy

IgE-mediated mast cell (MC) activation is a critical component of allergic responses to oral Ags. Several T cell-derived cytokines have been shown to promote MC reactivity, and we recently demonstrated a critical role for the cytokine IL-10 in mediating MC responses during food allergy. In this study, we further validate the role of IL-10 using Ab-mediated IL-10 depletion. IL-10 neutralization significantly attenuated MC responses, leading to decreased MC accumulation and activation, as well as inhibition of MC-mediated symptoms such as allergic diarrhea. This was accompanied by decreased Th2 cytokine gene expression, attenuated systemic T cell responses, and fewer CD4 T cells, B cells, and MCs in the spleen. Our data further confirm the role of IL-10 in driving MC responses and suggest that IL-10-responsive MCs may constitute an important player in allergic responses.

IL-10 Differentially Promotes Mast Cell Responsiveness to IL-33, Resulting in Enhancement of Type 2 Inflammation and Suppression of Neutrophilia

Mast cells (MCs) play critical roles in the establishment of allergic diseases. We recently demonstrated an unexpected, proinflammatory role for IL-10 in regulating MC responses. IL-10 enhanced MC activation and promoted IgE-dependent responses during food allergy. However, whether these effects extend to IgE-independent stimuli is not clear. In this article, we demonstrate that IL-10 plays a critical role in driving IL-33-mediated MC responses. IL-10 stimulation enhanced MC expansion and degranulation, ST2 expression, IL-13 production, and phospho-relA upregulation in IL-33-treated cells while suppressing TNF-α. These effects were partly dependent on endogenous IL-10 and further amplified in MCs coactivated with both IL-33 and IgE/Ag. IL-10's divergent effects also extended in vivo. In a MC-dependent model of IL-33-induced neutrophilia, IL-10 treatment enhanced MC responsiveness, leading to suppression of neutrophils and decreased TNF-α. In contrast, during IL-33-induced type 2 inflammation, IL-10 priming exacerbated MC activity, resulting in MC recruitment to various tissues, enhanced ST2 expression, induction of hypothermia, recruitment of eosinophils, and increased MCPT-1 and IL-13 levels. Our data elucidate an important role for IL-10 as an augmenter of IL-33-mediated MC responses, with implications during both allergic diseases and other MC-dependent disorders. IL-10 induction is routinely used as a prognostic marker of disease improvement. Our data suggest instead that IL-10 can enhance ST2 responsiveness in IL-33-activated MCs, with the potential to both aggravate or suppress disease severity depending on the inflammatory context.

Insights into the Characteristics and Functions of Mast Cells in the Gut

Mast cells have vital functions in allergic responses and parasite ejection, while the underlying mechanisms remain unclear. Meanwhile, MCs are essential for the maintenance of GI barrier function, and their interactions with neurons, immune cells, and epithelial cells have been related to various gastrointestinal (GI) disorders. An increasing number of investigations are being disclosed, with a lack of inner connections among them. This review aims to highlight their properties and categorization and further delve into their participation in GI diseases via interplay with neurons and immune cells. We also discuss their roles in diseases like inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). Based on the evidence, we advocated for their potential application in clinical practices and advocated future research prospects.

Role of mast cells activation in the tumor immune microenvironment and immunotherapy of cancers

The mast cell is an important cellular component that plays a crucial role in the crosstalk between innate and adaptive immune responses within the tumor microenvironment (TME). Recently, numerous studies have indicated that mast cells related to tumors play a dual role in regulating cancers, with conflicting results seemingly determined by the degranulation medium. As such, mast cells are an ignored but very promising potential target for cancer immunotherapy based on their immunomodulatory function. In this review, we present a comprehensive overview of the roles and mechanisms of mast cells in diverse cancer types. Firstly, we evaluated the infiltration density and location of mast cells on tumor progression. Secondly, mast cells are activated by the TME and subsequently release a range of inflammatory mediators, cytokines, chemokines, and lipid products that modulate their pro-or anti-tumor functions. Thirdly, activated mast cells engage in intercellular communication with other immune or stromal cells to modulate the immune status or promote tumor development. Finally, we deliberated on the clinical significance of targeting mast cells as a therapeutic approach to restrict tumor initiation and progression. Overall, our review aims to provide insights for future research on the role of mast cells in tumors and their potential as therapeutic targets for cancer treatment.

SCF and IL-33 regulate mouse mast cell phenotypic and functional plasticity supporting a pro-inflammatory microenvironment

Mast cells (MCs) are multifaceted innate immune cells often present in the tumor microenvironment (TME). Several recent findings support their contribution to the transition from chronic inflammation to cancer. However, MC-derived mediators can either favor tumor progression, inducing the spread of the tumor, or exert anti-tumorigenic functions, limiting tumor growth. This apparent controversial role likely depends on the plastic nature of MCs that under different microenvironmental stimuli can rapidly change their phenotype and functions. Thus, the exact effect of unique MC subset(s) during tumor progression is far from being understood. Using a murine model of colitis-associated colorectal cancer, we initially characterized the MC population within the TME and in non-lesional colonic areas, by multicolor flow cytometry and confocal microscopy. Our results demonstrated that tumor-associated MCs harbor a main connective tissue phenotype and release high amounts of Interleukin (IL)-6 and Tumor Necrosis Factor (TNF)-α. This MC phenotype correlates with the presence of high levels of Stem Cell Factor (SCF) and IL-33 inside the tumor. Thus, we investigated the effect of SCF and IL-33 on primary MC cultures and underscored their ability to shape MC phenotype eliciting the production of pro-inflammatory cytokines. Our findings support the conclusion that during colonic transformation a sustained stimulation by SCF and IL-33 promotes the accumulation of a prevalent connective tissue-like MC subset that through the secretion of IL-6 and TNF-α maintains a pro-inflammatory microenvironment.

A Deep View of the Biological Property of Interleukin-33 and Its Dysfunction in the Gut

Intestinal diseases have always posed a serious threat to human health, with inflammatory bowel disease (IBD) being one of them. IBD is an autoimmune disease characterized by chronic inflammation, including ulcerative colitis (UC) and Crohn's disease (CD). The "alarm" cytokine IL-33, which is intimately associated with Th2 immunity, is a highly potent inflammatory factor that is considered to have dual functions-operating as both a pro-inflammatory cytokine and a transcriptional regulator. IL-33 has been shown to play a crucial role in both the onset and development of IBD. Therefore, this review focuses on the pathogenesis of IBD, the major receptor cell types, and the activities of IL-33 in innate and adaptive immunity, as well as its underlying mechanisms and conflicting conclusions in IBD. We have also summarized different medicines targeted to IL-33-associated diseases. Furthermore, we have emphasized the role of IL-33 in gastrointestinal cancer and parasitic infections, giving novel prospective therapeutic utility in the future application of IL-33.

Helper innate lymphoid cells as cell therapy for cancer

Although the first cancer immunotherapy was given in the clinic more than a century ago, this line of treatment has remained more of a distant goal than a practical therapy due to limited understanding of the tumour microenvironment and the mechanisms at play within it, which led to failures of numerous clinical trials. However, in the last two decades, the immune checkpoint inhibitors (ICIs) and chimeric antigen receptor-T cell therapies have revolutionized the treatment of cancer and provided proof-of-concept that immunotherapies are a viable option. So far, immunotherapies have majoritarily focused on utilizing T cells; however, T cells are not autonomous but rather function as part of, and therefore are influenced by, a vast cast of other immune cells, including innate lymphoid cells (ILCs). Here, we summarize the role of ILCs, especially helper ILCs, in tumour development, progression and metastasis, as well as their potential to be used as immunotherapy for cancer. By reviewing the studies that used helper ILCs as adoptive cell therapy (ACT), we highlight the rationale behind considering these cells as novel ACT for cancer as well as identify open questions and areas for future research.

The Controversial Role of Intestinal Mast Cells in Colon Cancer

Mast cells are tissue-resident sentinels involved in large number of physiological and pathological processes, such as infection and allergic response, thanks to the expression of a wide array of receptors. Mast cells are also frequently observed in a tumor microenvironment, suggesting their contribution in the transition from chronic inflammation to cancer. In particular, the link between inflammation and colorectal cancer development is becoming increasingly clear. It has long been recognized that patients with inflammatory bowel disease have an increased risk of developing colon cancer. Evidence from experimental animals also implicates the innate immune system in the development of sporadically occurring intestinal adenomas, the precursors to colorectal cancer. However, the exact role of mast cells in tumor initiation and growth remains controversial: mast cell-derived mediators can either exert pro-tumorigenic functions, causing the progression and spread of the tumor, or anti-tumorigenic functions, limiting the tumor's growth. Here, we review the multifaceted and often contrasting findings regarding the role of the intestinal mast cells in colon cancer progression focusing on the molecular pathways mainly involved in the regulation of mast cell plasticity/functions during tumor progression.

Focus on mast cells in the tumor microenvironment: Current knowledge and future directions

Mast cells (MCs) are crucial cells participating in both innate and adaptive immune processes that play important roles in protecting human health and in the pathophysiology of various diseases, such as allergies, cardiovascular diseases, and autoimmune diseases. In the context of tumors, MCs are a non-negligible population of immune cells in the tumor microenvironment (TME). In most tumor types, MCs accumulate in both the tumor tissue and the surrounding tissue. MCs interact with multiple components of the TME, affecting TME remodeling and the tumor cell fate. However, controversy persists regarding whether MCs contribute to tumor progression or trigger an anti-tumor immune response. This review focuses on the context of the TME to explore the specific properties and functions of MCs and discusses the crosstalk that occurs between MCs and other components of the TME, which affect tumor angiogenesis and lymphangiogenesis, invasion and metastasis, and tumor immunity through different mechanisms. We also anticipate the potential role of MCs in cancer immunotherapy, which might expand upon the success achieved with existing cancer therapies.

Comparative Study of the Role of Interepithelial Mucosal Mast Cells in the Context of Intestinal Adenoma-Carcinoma Progression

Mast cells (MCs) are crucial players in the relationship between the tumor microenvironment (TME) and cancer cells and have been shown to influence angiogenesis and progression of human colorectal cancer (CRC). However, the role of MCs in the TME is controversially discussed as either pro- or anti-tumorigenic. Genetically engineered mouse models (GEMMs) are the most frequently used in vivo models for human CRC research. In the murine intestine there are at least three different MC subtypes: interepithelial mucosal mast cells (ieMMCs), lamina proprial mucosal mast cells (lpMMCs) and connective tissue mast cells (CTMCs). Interepithelial mucosal mast cells (ieMMCs) in (pre-)neoplastic intestinal formalin-fixed paraffin-embedded (FFPE) specimens of mouse models (total lesions n = 274) and human patients (n = 104) were immunohistochemically identified and semiquantitatively scored. Scores were analyzed along the adenoma-carcinoma sequence in humans and 12 GEMMs of small and large intestinal cancer. The presence of ieMMCs was a common finding in intestinal adenomas and carcinomas in mice and humans. The number of ieMMCs decreased in the course of colonic adenoma-carcinoma sequence in both species (p < 0.001). However, this dynamic cellular state was not observed for small intestinal murine tumors. Furthermore, ieMMC scores were higher in GEMMs with altered Wnt signaling (active β-catenin) than in GEMMs with altered MAPK signaling and wildtypes (WT). In conclusion, we hypothesize that, besides stromal MCs (lpMMCs/CTMCs), particularly the ieMMC subset is important for onset and progression of intestinal neoplasia and may interact with the adjacent neoplastic epithelial cells in dependence on the molecular environment. Moreover, our study indicates the need for adequate GEMMs for the investigation of the intestinal immunologic TME.

TCF-1: a maverick in T cell development and function

The T cell-specific DNA-binding protein TCF-1 is a central regulator of T cell development and function along multiple stages and lineages. Because it interacts with β-catenin, TCF-1 has been classically viewed as a downstream effector of canonical Wnt signaling, although there is strong evidence for β-catenin-independent TCF-1 functions. TCF-1 co-binds accessible regulatory regions containing or lacking its conserved motif and cooperates with other nuclear factors to establish context-dependent epigenetic and transcription programs that are essential for T cell development and for regulating immune responses to infection, autoimmunity and cancer. Although it has mostly been associated with positive regulation of chromatin accessibility and gene expression, TCF-1 has the potential to reduce chromatin accessibility and thereby suppress gene expression. In addition, the binding of TCF-1 bends the DNA and affects the chromatin conformation genome wide. This Review discusses the current understanding of the multiple roles of TCF-1 in T cell development and function and their mechanistic underpinnings.

ST8Sia6 Promotes Tumor Growth in Mice by Inhibiting Immune Responses

Many tumors exhibit increased incorporation of sialic acids into cell-surface glycans, which impact the tumor microenvironment. Sialic acid immunoglobulin-like lectins (Siglec) are receptors that recognize sialic acids and modulate immune responses, including responses to tumors. However, the roles of individual sialyltransferases in tumorigenesis and tumor growth are not well understood. Here, we examined the sialyltransferase ST8Sia6, which generated α2,8-linked disialic acids that bind to murine Siglec-E and human Siglec-7 and -9. Increased ST8Sia6 expression was found on many human tumors and associated with decreased survival in several cancers, including colon cancer. Because of this, we engineered MC38 and B16-F10 tumor lines to express ST8Sia6. ST8Sia6-expressing MC38 and B16-F10 tumors exhibited faster growth and led to decreased survival, which required host Siglec-E. ST8Sia6 expression on tumors also altered macrophage polarization toward M2, including upregulation of the immune modulator arginase, which also required Siglec-E. ST8Sia6 also accelerated tumorigenesis in a genetically engineered, spontaneous murine model of colon cancer, decreasing survival from approximately 6 months to 67 days. Thus, ST8Sia6 expression on tumors inhibits antitumor immune responses to accelerate tumor growth.

Mechanisms of Immunosuppression in Colorectal Cancer

Simple Summary

More emerging studies are exploring immunotherapy for solid cancers, including colorectal cancer. Besides, checkpoint blockade immunotherapy and chimeric antigen receptor (CAR) -based immune cell therapy have being examined in clinical trials for colorectal cancer patients. However, immunosuppression that leads to the blockage of normal immunosurveillance often leads to cancer development and relapse. In this study, we systematically reviewed the mechanism of immunosuppression, specifically in colorectal cancer, from different perspectives, including the natural or induced immunosuppressive cells, cell surface protein, cytokines/chemokines, transcriptional factors, metabolic alteration, phosphatase, and tissue hypoxia in the tumor microenvironment. We also discussed the progress of immunotherapies in clinical trials/studies for colorectal cancer and highlighted how different strategies for cancer therapy targeted the immunosuppression reviewed above. Our review provides some timely implications for restoring immunosurveillance to improve treatment efficacy in colorectal cancer (CRC).

Abstract

CRC is the third most diagnosed cancer in the US with the second-highest mortality rate. A multi-modality approach with surgery/chemotherapy is used in patients with early stages of colon cancer. Radiation therapy is added to the armamentarium in patients with locally advanced rectal cancer. While some patients with metastatic CRC are cured, the majority remain incurable and receive palliative chemotherapy as the standard of care. Recently, immune checkpoint blockade has emerged as a promising treatment for many solid tumors, including CRC with microsatellite instability. However, it has not been effective for microsatellite stable CRC. Here, main mechanisms of immunosuppression in CRC will be discussed, aiming to provide some insights for restoring immunosurveillance to improve treatment efficacy in CRC.

Group 2 Innate Lymphoid Cells: A Double-Edged Sword in Cancer?

Group 2 Innate Lymphoid Cells (ILC2s) belong to the family of helper ILCs which provide host defense against infectious agents, participate in inflammatory responses and mediate lymphoid organogenesis and tissue repair, mainly at the skin and mucosal level. Based on their transcriptional, phenotypic and functional profile, ILC2s mirror the features of the adaptive CD4+ Th2 cell subset, both contributing to the so-called type 2 immune response. Similar to other ILCs, ILC2s are rapidly activated by signals deriving from tissue and/or other tissue-resident immune cells. The biologic activity of ILCs needs to be tightly regulated in order to prevent them from contributing to severe inflammation and damage in several organs. Indeed, ILC2s display both enhancing and regulatory roles in several pathophysiological conditions, including tumors. In this review, we summarize the actual knowledge about ILC2s ability to induce or impair a protective immune response, their pro- or antitumor activity in murine models, human (children and adults) pathologies and the potential strategies to improve cancer immunotherapy by exploiting the features of ILC2s.

IL33 and Mast Cells-The Key Regulators of Immune Responses in Gastrointestinal Cancers?

The Interleukin (IL-)1 family IL33 is best known for eliciting type 2 immune responses by stimulating mast cells (MCs), regulatory T-cells (Tregs), innate lymphoid cells (ILCs) and other immune cells. MCs and IL33 provide critical control of immunological and epithelial homeostasis in the gastrointestinal (GI) tract. Meanwhile, the role of MCs in solid malignancies appears tissue-specific with both pro and anti-tumorigenic activities. Likewise, IL33 signaling significantly shapes immune responses in the tumor microenvironment, but these effects remain often dichotomous when assessed in experimental models of cancer. Thus, the balance between tumor suppressing and tumor promoting activities of IL33 are highly context dependent, and most likely dictated by the mixture of cell types responding to IL33. Adding to this complexity is the promiscuous nature by which MCs respond to cytokines other than IL33 and release chemotactic factors that recruit immune cells into the tumor microenvironment. In this review, we integrate the outcomes of recent studies on the role of MCs and IL33 in cancer with our own observations in the GI tract. We propose a working model where the most abundant IL33 responsive immune cell type is likely to dictate an overall tumor-supporting or tumor suppressing outcome in vivo. We discuss how these opposing responses affect the therapeutic potential of targeting MC and IL33, and highlight the caveats and challenges facing our ability to effectively harness MCs and IL33 biology for anti-cancer immunotherapy.

Autism Spectrum Disorders: Role of Pre- and Post-Natal GammaDelta (γδ) T Cells and Immune Regulation

BACKGROUND

It is widely accepted that alterations in immune functioning are an important aspect of the pathoetiology and pathophysiology of autism spectrum disorders (ASD). A relatively under-explored aspect of these alterations is the role of gammaDelta (γδ) T cells, prenatally and in the postnatal gut, which seem important hubs in driving the course of ASD.

METHODS

The present article describes the role of γδ T cells in ASD, including their interactions with other immune cells shown to be altered in this spectrum of conditions, including natural killer cells and mast cells.

RESULTS

Other risk factors in ASD, such as decreased vitamins A & D, as well as toxin-associated activation of the aryl hydrocarbon receptor, may also be intimately linked to γδ T cells, and alterations in the regulation of these cells. A growing body of data has highlighted an important role for alterations in mitochondria functioning in the regulation of immune cells, including natural killer cells and mast cells. This is an area that requires investigation in γδ T cells and their putative subtypes.

CONCLUSION

It is also proposed that maternal stress may act through alterations in the maternal microbiome, leading to changes in how the balance of short-chain fatty acids, such as butyrate, which may act to regulate the placenta and foetal development. Following an overview of previous research on immune, especially γδ T cells, effects in ASD, the future research implications are discussed in detail.

Ambiguous roles and potential therapeutic strategies of innate lymphoid cells in different types of tumor

Recent years have witnessed a significant development in the current understanding of innate lymphoid cells (ILCs) and their roles in the innate immune system, where they regulate tissue homeostasis, inflammation, as well as tumor surveillance and tumorigenesis. Based on the limited studies of ILCs in cancer, ILCs may be classified into three subgroups depending on their phenotypic and functional characteristics: Group 1 ILCs, which include natural killer cells and ILC1s; Group 2 ILCs, which only contain ILC2s and Group 3 ILCs, which comprise of LTi cells and ILC3s. Group 1 ILCs predominantly exert antitumor activities, while Group 2 ILCs and Group 3 ILCs are predominantly procarcinogenic in nature. In different types of tumor, each ILC subset behaves differently. Current research is focused on investigating how ILCs may be manipulated and employed as therapeutic strategies for the treatment of cancer. The present review aimed to summarize the characteristics and effects of ILCs in the context of tumor immunology, and provide novel insight into the pro- or anti-tumor activities of ILCs in different types of malignancy, including solid tumors, such as those in the gastrointestinal tract, lung, breast, bladder or prostate, as well as melanoma, further to hematological malignancies, with the aim to highlight potential therapeutic targets for the treatment of cancer.

IL-9 and IL-9-producing cells in tumor immunity

Abstract

Interleukin (IL)-9 belongs to the IL-2Rγc chain family and is a multifunctional cytokine that can regulate the function of many kinds of cells. It was originally identified as a growth factor of T cells and mast cells. In previous studies, IL-9 was mainly involved in the development of allergic diseases, autoimmune diseases and parasite infections. Recently, IL-9, as a double-edged sword in the development of cancers, has attracted extensive attention. Since T-helper 9 (Th9) cell-derived IL-9 was verified to play a powerful antitumor role in solid tumors, an increasing number of researchers have started to pay attention to the role of IL-9-skewed CD8⁺ T (Tc9) cells, mast cells and Vδ2 T cell-derived IL-9 in tumor immunity. Here, we review recent studies on IL-9 and several kinds of IL-9-producing cells in tumor immunity to provide useful insight into tumorigenesis and treatment.

Mast cells-derived MiR-223 destroys intestinal barrier function by inhibition of CLDN8 expression in intestinal epithelial cells

Background

Mast cells (MCs) have been found to play a critical role during development of inflammatory bowel disease (IBD) that characterized by dysregulation of inflammation and impaired intestinal barrier function. However, the function of MCs in IBD remains to be fully elucidated.

Results

In our study, we used exosomes isolated from human mast cells-1 (HMCs-1) to culture with NCM460, HT-29 or CaCO2 of intestinal epithelial cells (IECs) to investigate the communication between MCs and IECs. We found that MCs-derived exosomes significantly increased intestinal epithelial permeability and destroyed intestinal barrier function, which is attributed to exosome-mediated functional miRNAs were transferred from HMCs-1 into IECs, leading to inhibit tight junction-related proteins expression, including tight junction proteins 1 (TJP1, ZO-1), Occludin (OCLN), Claudin 8 (CLDN8). Microarray and bioinformatic analysis have further revealed that a panel of miRNAs target different tight junction-related proteins. Interestingly, miR-223 is enriched in mast cell-derived exosome, which inhibit CLDN8 expression in IECs, while treatment with miR-223 inhibitor in HT-29 cells significantly reversed the inhibitory effect of HMCs-1-derived exosomes on CLDN 8 expression. Most importantly, enrichment of MCs accumulation in intestinal mucosa of patients with IBD compared with those healthy control.

Conclusions

These results indicated that enrichment of exosomal miR-223 from HMCs-1 inhibited CLDN8 expression, leading to destroy intestinal barrier function. These finding provided a novel insight of MCs as a new target for therapeutic treatment of IBD.

Beyond IgE: Alternative Mast Cell Activation Across Different Disease States

Mast cells are often regarded through the lens of IgE-dependent reactions as a cell specialized only for anti-parasitic and type I hypersensitive responses. However, recently many researchers have begun to appreciate the expansive repertoire of stimuli that mast cells can respond to. After the characterization of the interleukin (IL)-33/suppression of tumorigenicity 2 (ST2) axis of mast cell activation-a pathway that is independent of the adaptive immune system-researchers are revisiting other stimuli to induce mast cell activation and/or subsequent degranulation independent of IgE. This discovery also underscores that mast cells act as important mediators in maintaining body wide homeostasis, especially through barrier defense, and can thus be the source of disease as well. Particularly in the gut, inflammatory bowel diseases (Crohn's disease, ulcerative colitis, etc.) are characterized with enhanced mast cell activity in the context of autoimmune disease. Mast cells show phenotypic differences based on tissue residency, which could manifest as different receptor expression profiles, allowing for unique mast cell responses (both IgE and non-IgE mediated) across varying tissues as well. This variety in receptor expression suggests mast cells respond differently, such as in the gut where immunosuppressive IL-10 stimulates the development of food allergy or in the lungs where transforming growth factor-β1 (TGF-β1) can enhance mast cell IL-6 production. Such differences in receptor expression illustrate the truly diverse effector capabilities of mast cells, and careful consideration must be given toward the phenotype of mast cells observed in vitro. Given mast cells' ubiquitous tissue presence and their capability to respond to a broad spectrum of non-IgE stimuli, it is expected that mast cells may also contribute to the progression of autoimmune disorders and other disease states such as metastatic cancer through promoting chronic inflammation in the local tissue microenvironment and ultimately polarizing toward a unique T_h17 immune response. Furthermore, these interconnected, atypical activation pathways may crosstalk with IgE-mediated signaling differently across disorders such as parasitism, food allergies, and autoimmune disorders of the gut. In this review, we summarize recent research into familiar and novel pathways of mast cells activation and draw connections to clinical human disease.

Therapeutic Targeting of the Colorectal Tumor Stroma

Colorectal tumors have been classified based on histologic factors, genetic factors, and consensus molecular subtypes, all of which affect the tumor microenvironment. Elements of the tumor microenvironment serve as therapeutic targets and might be used as prognostic factors. For example, immune checkpoint inhibitors are used to treat tumors with microsatellite instability, and anti-angiogenic agents may be used in combination with other drugs to slow or inhibit tumor growth. We review the features of the colorectal tumor stroma that are associated with patient outcomes and discuss potential therapeutic agents that target these features.

Cell Intrinsic Deregulated ß-Catenin Signaling Promotes Expansion of Bone Marrow Derived Connective Tissue Type Mast Cells, Systemic Inflammation, and Colon Cancer

Mast cells constitutively express ß-catenin and expand in solid tumors such as colon and skin cancer. However, the role of ß-catenin signaling in mast cells and the cause or effect of mast cell expansion and tumor growth has yet to be established. In earlier studies we used mast cell depletion and protease staining approaches, to provide evidence for a causative role of mast cells in small bowel polyposis, and related specific phenotypes and distributions of tumor infiltrating mast cells to stages of tumor growth. Here we report that, stabilization of ß-catenin expands mast cells to promote high incidence of colon polyposis and infrequent small bowel polyps and skin cancer. Expression of a dominant acting ß-catenin in mast cells (5CreCAT) stimulated maturation and expression of granule stored proteases. Both mucosal and connective tissue type mast cells accumulated in colonic small bowel polyps independent of gender, and mice developed chronic systemic inflammation with splenomegaly. Reconstitution of polyposis-prone mice with bone marrow from 5CreCAT mice resulted in focal expansion of connective tissue like mast cells, which are normally rare in benign polyps and characteristically expand during adenoma-to-carcinoma transition. Our findings highlight a hitherto unknown contribution of ß-catenin signaling in mast cells to their maturation and to increased risk of colon cancer.

IL-33 – positive or negative role in cancer progression?

Interleukin-33 (IL-33) is a IL-1 family member of cytokines which binds the ST2 (suppression of tumorigenicity 2) receptor. This cytokine has a dual function. It may act both as a traditional cytokine and as an intracellular nuclear factor. IL-33 plays a role in many diseases such as: allergy, inflammatory diseases, diabetes and heart diseases. The role of IL-33 in the development of cancer has been intensively studied in recent years and researchers observe both its pro- -and anti-cancer effects. IL-33 promotes the development of tumors by affecting expression of cytokines promoting proliferation, angiogenesis, migration, matrix remodeling, the inhibition of apoptosis and recruitment of individual cells of the immune system. Antitumor action of IL-33 is carried out by recruiting and activating CD8+T lymphocytes, natural killer (NK) cells and by promoting second type immune response by the type 2 innate lymphoid cells (ILC2). Despite numerous studies on the role of IL-33 in the development of cancer, we still do not fully understand the mechanisms by which IL-33 impacts the development and malignancy of various types of cancers. This review summarizes the dual role of IL-33 in the development of the most common cancers in the world to better understand its importance in the carcinogenesis.

Mast Cells and Sensory Nerves Contribute to Neurogenic Inflammation and Pruritus in Chronic Skin Inflammation

The intimate interaction between mast cells and sensory nerves can be illustrated by the wheal and surrounding flare in an urticarial reaction in human skin. This reaction is typically associated with an intense itch at the reaction site. Upon activation, cutaneous mast cells release powerful mediators, such as histamine, tryptase, cytokines, and growth factors that can directly stimulate corresponding receptors on itch-mediating sensory nerves. These include, e.g., H1- and H4-receptors, protease-activated receptor-2, IL-31 receptor, and the high-affinity receptor of nerve growth factor (TrkA). On the other hand, sensory nerves can release neuropeptides, including substance P and vasoactive intestinal peptide, that are able to stimulate mast cells to release mediators leading to potentiation of the reciprocal interaction, inflammation, and itch. Even though mast cells are well recognized for their role in allergic skin whealing and urticaria, increasing evidence supports the reciprocal function between mast cells and sensory nerves in neurogenic inflammation in chronic skin diseases, such as psoriasis and atopic dermatitis, which are often characterized by distressing itch, and exacerbated by psychological stress. Increased morphological contacts between mast cells and sensory nerves in the lesional skin in psoriasis and atopic dermatitis as well as experimental models in mice and rats support the essential role for mast cell-sensory nerve communication in consequent pruritus. Therefore, we summarize here the present literature pointing to a close association between mast cells and sensory nerves in pruritic skin diseases as well as review the essential supporting findings on pruritic models in mice and rats.

Future Needs in Mast Cell Biology

The pathophysiological roles of mast cells are still not fully understood, over 140 years since their description by Paul Ehrlich in 1878. Initial studies have attempted to identify distinct "subpopulations" of mast cells based on a relatively small number of biochemical characteristics. More recently, "subtypes" of mast cells have been described based on the analysis of transcriptomes of anatomically distinct mouse mast cell populations. Although mast cells can potently alter homeostasis, in certain circumstances, these cells can also contribute to the restoration of homeostasis. Both solid and hematologic tumors are associated with the accumulation of peritumoral and/or intratumoral mast cells, suggesting that these cells can help to promote and/or limit tumorigenesis. We suggest that at least two major subsets of mast cells, MC1 (meaning anti-tumorigenic) and MC2 (meaning pro-tumorigenic), and/or different mast cell mediators derived from otherwise similar cells, could play distinct or even opposite roles in tumorigenesis. Mast cells are also strategically located in the human myocardium, in atherosclerotic plaques, in close proximity to nerves and in the aortic valve. Recent studies have revealed evidence that cardiac mast cells can participate both in physiological and pathological processes in the heart. It seems likely that different subsets of mast cells, like those of cardiac macrophages, can exert distinct, even opposite, effects in different pathophysiological processes in the heart. In this chapter, we have commented on possible future needs of the ongoing efforts to identify the diverse functions of mast cells in health and disease.

Tumor microenvironment and stroma in intestinal adenocarcinomas and associated metastases in Atlantic salmon broodfish (Salmo salar)

Animal models are invaluable tools in cancer research. In this context, salmon is a promising candidate. Intestinal adenocarcinoma with metastases may be induced as a consequence of a plant-based diet triggering the inflammation - dysplasia- carcinogenesis pathway. Here, we investigate the stroma and the presence and nature of immune cells in such tumors by staining for mast cells, immunohistochemistry for T cells and antigen-presenting cells and in situ hybridization for B cells. In intestinal tumors, substantial amounts of T cells were detected in the stroma, whilst MHC class II⁺ cells were mainly among the cancerous cells. Ig⁺ cells were observed primarily in the tumor periphery. Mast cells showed a strong association with stroma. In metastases, scarce amounts of T cells were detected, whilst MHC I and II-reactivity varied, some tumors being completely negative. Ig⁺ cells were scattered around the metastatic tissue in no particular pattern, but were occasionally observed within clusters of tumor cells. Small numbers of mast cells were detected in the stroma. To the best of our knowledge, this is the first report addressing immune cells in fish tumors. The teleost tumor microenvironment seems comparable to that of mammals, making fish interesting model animals in oncoimmunology research.

The role of helper innate lymphoid cells in cancer

Innate lymphoid cells (ILCs) are an emerging family of innate immune cells and have been found to have an important role in infection, inflammation and tissue repair. In particular, recent work has identified significant alterations of ILC responses in tumor patients, suggesting potential roles of ILCs in tumor development. In this paper, we have focused on the basic features of ILCs and their interaction with other immune cells. Importantly, as the role of cytotoxic natural killer cells, assigned to ILC1 family, in cancer has been well established, we have summarized the new findings that showcase the potential role and mechanism of helper ILCs in different tumors. Helper ILCs might promote or inhibit tumor growth and metastasis, which depends on tumor type and ILC subset.

Intake consumption of ginsenoside Rg3, profiling of selected cytokines, and development of rectal polyps

Background: Rectal polyps is a major risk factor for rectal cancer. There is a need to explore a panel of preventive measures, as well as reliable biomarkers for screening of rectal polyps.

Patients and methods: We conducted a case control study which aimed to explore the effects of regular consumption of ginsenoside Rg3, profiling of selected cytokines, and development of rectal polyps in a Chinese population.

Results: Significantly higher levels of IL-4, MIP-1β, FasL, TGF-β1, and RANTES were detected in rectal polyp cases. Further, we found significant dose-response relationships between quartile-categorized levels of IL-4, MIP-1β, FasL, and TGF-β1, and risk of rectal polyps. The strongest associations for IL-4, MIP-1β, FasL, and TGF-β1 were observed for the highest quartile vs the lowest quartile with an OR of 1.78, 2.70, 1.49, and 2.36, respectively. Compared with non-Rg3 consumers, regular Rg3 consumers had a significantly lower risk of rectal polyps (OR =0.71; 95% CI: 0.55–0.92; P=0.009). We also found that Rg3 consumers had significantly lower levels of IL-4, MIP-1β, FasL, and TGF-β1 than non-Rg3 consumers, in both rectal polyp cases and healthy controls.

Conclusion: These results indicate that regular consumption of Rg3 might prevent the occurrence of rectal polyps through decreasing the serum level of selected cytokines, including IL-4, MIP-1β, FasL, and TGF-β1. Further clinical trials and prospective cohort studies with larger sample sizes are warranted to validate the anti-inflammatory activity and the anti-tumorigenic role of Rg3.

Lysosomotropic challenge of mast cells causes intra-granular reactive oxygen species production

Mast cells contribute to the pathology of allergic and other disorders. Strategies to interfere with harmful mast cell-related activities are therefore warranted. Previously we established a principle for inducing selective apoptosis of mast cells, by the use of lysosomotropic agents that cause secretory granule permeabilization, leading to production of reactive oxygen species (ROS). However, the mechanism of ROS production has not been known. Here we addressed this issue. Live microscopy analysis showed that the secretory granules comprise major subcellular compartments for ROS production in response to mefloquine. As further signs for the primary involvement of secretory granules, both ROS production and cell death was blunted in mast cells lacking serglycin, a secretory granule-restricted proteoglycan. Inhibition of granule acidification caused an essentially complete blockade of granule permeabilization, ROS production and cell death in response to mefloquine. ROS production was also attenuated in the presence of an iron chelator, and after inhibition of either granzyme B or the ERK1/2 MAP kinase signaling pathway. Together, our findings reveal that the mast cell secretory granules constitute major sites for ROS production in mast cells subjected to lysosomotropic challenge. Moreover, this study reveals a central role for granule acidification in ROS generation and the pro-apoptotic response triggered downstream of secretory granule permeabilization.

Mast Cell Activation and KSHV Infection in Kaposi Sarcoma

Purpose: Kaposi sarcoma (KS) is a vascular tumor initiated by infection of endothelial cells (ECs) with KS-associated herpesvirus (KSHV). KS is dependent on sustained proinflammatory signals provided by intralesional leukocytes and continued infection of new ECs. However, the sources of these cytokines and infectious virus within lesions are not fully understood. Here, mast cells (MCs) are identified as proinflammatory cells within KS lesions that are permissive for, and activated by, infection with KSHV.Experimental Design: Three validated MC lines were used to assess permissivity of MCs to infection with KSHV and to evaluate MCs activation following infection. Biopsies from 31 AIDS-KS cases and 11 AIDS controls were evaluated by IHC for the presence of MCs in KS lesions and assessment of MC activation state and infection with KSHV. Plasma samples from 26 AIDS-KS, 13 classic KS, and 13 healthy adults were evaluated for levels of MC granule contents tryptase and histamine.Results: In culture, MCs supported latent and lytic KSHV infection, and infection-induced MC degranulation. Within KS lesions, MCs were closely associated with spindle cells. Furthermore, MC activation was extensive within patients with KS, reflected by elevated circulating levels of tryptase and a histamine metabolite. One patient with clinical signs of extensive MC activation was treated with antagonists of MC proinflammatory mediators, which resulted in a rapid and durable regression of AIDS-KS lesions.Conclusions: Using complimentary in vitro and in vivo studies we identify MCs as a potential long-lived reservoir for KSHV and a source of proinflammatory mediators within the KS lesional microenvironment. In addition, we identify MC antagonists as a promising novel therapeutic approach for KS. Clin Cancer Res; 24(20); 5085-97. ©2018 AACR.

The Role of IL-33/ST2 Pathway in Tumorigenesis

Cancer is initiated by mutations in critical regulatory genes; however, its progression to malignancy is aided by non-neoplastic cells and molecules that create a permissive environment known as the tumor stroma or microenvironment (TME). Interleukin 33 (IL-33) is a dual function cytokine that also acts as a nuclear factor. IL-33 typically resides in the nucleus of the cells where it is expressed. However, upon tissue damage, necrosis, or injury, it is quickly released into extracellular space where it binds to its cognate receptor suppression of tumorigenicity 2 (ST2)L found on the membrane of target cells to potently activate a T Helper 2 (Th2) immune response, thus, it is classified as an alarmin. While its role in immunity and immune-related disorders has been extensively studied, its role in tumorigenesis is only beginning to be elucidated and has revealed opposing roles in tumor development. The IL-33/ST2 axis is emerging as a potent modulator of the TME. By recruiting a cohort of immune cells, it can remodel the TME to promote malignancy or impose tumor regression. Here, we review its multiple functions in various cancers to better understand its potential as a therapeutic target to block tumor progression or as adjuvant therapy to enhance the efficacy of anticancer immunotherapies.