Interleukin 33 in tumor microenvironment is crucial for the accumulation and function of myeloid-derived suppressor cells

Myeloid‑derived suppressor cells as targets of emerging therapies and nanotherapies (Review)

Breast cancer (BC) is the leading cause of cancer-related mortality among women worldwide. Immunotherapies are a promising approach in cancer treatment, particularly for aggressive forms of BC with high mortality rates. However, the current eligibility for immunotherapy remains limited to a limited fraction of patients with BC. Myeloid-derived suppressor cells (MDSCs), originating from myeloid cells, are known for their dual role in immunosuppression and tumor promotion, significantly affecting patient outcomes by fostering the formation of premetastatic niches. Consequently, targeting MDSCs has emerged as a promising avenue for further exploration in therapeutic interventions. Leveraging nanotechnology-based drug delivery systems, which excel in accumulating drugs within tumors via passive or active targeting mechanisms, are a promising strategy for the use of MDSCs in the treatment of BC. The present review discusses the immunosuppressive functions of MDSCs, their role in BC, and the diverse strategies for targeting them in cancer therapy. Additionally, the present review discusses future advancements in BC treatments focusing on MDSCs. Furthermore, it elucidates the mechanisms underlying MDSC activation, recruitment and differentiation in BC progression, highlighting the clinical characteristics that render MDSCs suitable candidates for the therapy and targeted nanotherapy of BC.

Guardians and Mediators of Metastasis: Exploring T Lymphocytes, Myeloid-Derived Suppressor Cells, and Tumor-Associated Macrophages in the Breast Cancer Microenvironment

Breast cancers (BCs) are solid tumors composed of heterogeneous tissues consisting of cancer cells and an ever-changing tumor microenvironment (TME). The TME includes, among other non-cancer cell types, immune cells influencing the immune context of cancer tissues. In particular, the cross talk of immune cells and their interactions with cancer cells dramatically influence BC dissemination, immunoediting, and the outcomes of cancer therapies. Tumor-infiltrating lymphocytes (TILs), tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs) represent prominent immune cell populations of breast TMEs, and they have important roles in cancer immunoescape and dissemination. Therefore, in this article we review the features of TILs, TAMs, and MDSCs in BCs. Moreover, we highlight the mechanisms by which these immune cells remodel the immune TME and lead to breast cancer metastasis.

Unveiling the multifaceted antitumor effects of interleukin 33

Interleukin 33 (IL-33), once predominantly recognized for its pro-tumoral activities, has emerged as a multifunctional cytokine with antitumor properties. IL-33 pleiotropic activities include activation of Th1 CD4+ T cells, CD8+ T cells, NK cells, dendritic cells, eosinophils, as well as type 2 innate lymphoid cells. Regarding this immunomodulatory activity, IL-33 demonstrates synergistic interactions with various cancer therapies, including immune checkpoint blockade and chemotherapy. Combinatorial treatments leveraging IL-33 exhibit enhanced antitumor efficacy across different tumor models, promising novel avenues for cancer therapy. Despite its antitumor effects, the complex interplay of IL-33 within the tumor microenvironment underscores the need for further investigation. Understanding the mechanisms underlying IL-33's dual role as both a promoter and inhibitor of tumor progression is essential for refining therapeutic strategies and fully realizing its potential in cancer immunotherapy. This review delves into the intricate landscape of IL-33 effects within the tumor microenvironment, highlighting its pivotal role in orchestrating immune responses against cancer.

Interleukin 33 supports squamous cell carcinoma growth via a dual effect on tumour proliferation, migration and invasion, and T cell activation

Interleukin (IL)-33 is an important cytokine in the tumour microenvironment; it is known to promote the growth and metastasis of solid cancers, such as gastric, colorectal, ovarian and breast cancer. Our group demonstrated that the IL-33/ST2 pathway enhances the development of squamous cell carcinoma (SCC). Conversely, other researchers have reported that IL-33 inhibits tumour progression. In addition, the crosstalk between IL-33, cancer cells and immune cells in SCC remains unknown. The aim of this study was to investigate the effect of IL-33 on the biology of head and neck SCC lines and to evaluate the impact of IL-33 neutralisation on the T cell response in a preclinical model of SCC. First, we identified epithelial and peritumoural cells as a major local source of IL-33 in human SCC samples. Next, in vitro experiments demonstrated that the addition of IL-33 significantly increased the proliferative index, motility and invasiveness of SCC-25 cells, and downregulated MYC gene expression in SCC cell lines. Finally, IL-33 blockade significantly delayed SCC growth and led to a marked decrease in the severity of skin lesions. Importantly, anti-IL-33 monoclonal antibody therapy increase the percentage of CD4+IFNγ+ T cells and decreased CD4+ and CD8+ T cells secreting IL-4 in tumour-draining lymph nodes. Together, these data suggest that the IL-33/ST2 pathway may be involved in the crosstalk between the tumour and immune cells by modulating the phenotype of head and neck SCC and T cell activity. IL-33 neutralisation may offer a novel therapeutic strategy for SCC.

Myeloid-derived suppressor cells in cancer: therapeutic targets to overcome tumor immune evasion

Paradoxically, tumor development and progression can be inhibited and promoted by the immune system. After three stages of immune editing, namely, elimination, homeostasis and escape, tumor cells are no longer restricted by immune surveillance and thus develop into clinical tumors. The mechanisms of immune escape include abnormalities in antitumor-associated immune cells, selection for immune resistance to tumor cells, impaired transport of T cells, and the formation of an immunosuppressive tumor microenvironment. A population of distinct immature myeloid cells, myeloid-derived suppressor cells (MDSCs), mediate immune escape primarily by exerting immunosuppressive effects and participating in the constitution of an immunosuppressive microtumor environment. Clinical trials have found that the levels of MDSCs in the peripheral blood of cancer patients are strongly correlated with tumor stage, metastasis and prognosis. Moreover, animal experiments have confirmed that elimination of MDSCs inhibits tumor growth and metastasis to some extent. Therefore, MDSCs may become the target of immunotherapy for many cancers, and eliminating MDSCs can help improve the response rate to cancer treatment and patient survival. However, a clear definition of MDSCs and the specific mechanism involved in immune escape are lacking. In this paper, we review the role of the MDSCs population in tumor development and the mechanisms involved in immune escape in different tumor contexts. In addition, we discuss the use of these cells as targets for tumor immunotherapy. This review not only contributes to a systematic and comprehensive understanding of the essential role of MDSCs in immune system reactions against tumors but also provides information to guide the development of cancer therapies targeting MDSCs.

Macrophage: Hidden Criminal in Therapy Resistance

BACKGROUND

Although substantial efforts have been made by researchers to develop drugs, a disappointing reality is that the emergence of drug resistance is an unavoidable reality for the majority of patients. In recent years, emerging evidence suggests a connection between drug resistance and immune dysregulation.

SUMMARY

As a ubiquitously distributed, versatile innate immune cell, macrophages play essential roles in maintaining tissue homeostasis in a steady state. Nevertheless, it is becoming aware that macrophages undermine the action of therapeutic drugs across various disease types. Reprogramming macrophage function has been proven to be effective in restoring patient responsiveness to treatment. Herein, we comprehensively reviewed how macrophages respond to drugs and the mechanisms by which they contribute to treatment unresponsiveness in cancer, inflammatory diseases, and metabolic diseases. In addition, future prospects in macrophage-based combination therapy were discussed.

KEY MESSAGES

Targeting macrophages is a promising strategy for overcoming drug resistance in immune disorders.

Tumor microenvironment, histone modifications, and myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are important components of the tumor microenvironment (TME), which drive the tumor immune escape by inducing immunosuppression. The expansion and function of MDSCs are tightly associated with signaling pathways induced by molecules from tumor cells, stromal cells, and activated immune cells in the TME. Although these pathways have been well-characterized, the understanding of the epigenetic regulators involved is incomplete. Since histone modifications are the most studied epigenetic changes in MDSCs, we summarize current knowledge on the role of histone modifications in MDSCs within this review. We first discuss the influence of the TME on histone modifications in MDSCs, with an emphasis on histone modifications and modifiers that direct MDSC differentiation and function. Furthermore, we highlight current epigenetic interventions that can reverse MDSC-induced immunosuppression by modulating histone modifications and discuss future research directions to fully appreciate the role of histone modifications in MDSCs.

Decoding the IL-33/ST2 Axis: Its Impact on the Immune Landscape of Breast Cancer

Interleukin-33 (IL-33) has emerged as a critical cytokine in the regulation of the immune system, showing a pivotal role in the pathogenesis of various diseases including cancer. This review emphasizes the role of the IL-33/ST2 axis in breast cancer biology, its contribution to cancer progression and metastasis, its influence on the tumor microenvironment and cancer metabolism, and its potential as a therapeutic target. The IL-33/ST2 axis has been shown to have extensive pro-tumorigenic features in breast cancer, starting from tumor tissue proliferation and differentiation to modulating both cancer cells and anti-tumor immune response. It has also been linked to the resistance of cancer cells to conventional therapeutics. However, the role of IL-33 in cancer therapy remains controversial due to the conflicting effects of IL-33 in tumorigenesis and anti-tumor response. The possibility of targeting the IL-33/ST2 axis in tumor immunotherapy, or as an adjuvant in immune checkpoint blockade therapy, is discussed.

Interleukin-33 as a Potential Therapeutic Target in Gastric Cancer Patients: Current Insights

Gastric cancer is a significant global health problem as it is the fifth most prevalent cancer worldwide and the fourth leading cause of cancer-related mortality. While cytotoxic chemotherapy remains the primary treatment for advanced GC, response rates are limited. Recent progresses, focused on molecular signalling within gastric cancer, have ignited new hope for potential therapeutic targets that may improve survival and/or reduce the toxic effects of traditional therapies. Carcinomas are generally initiated when critical regulatory genes get mutated, but the progression to malignancy is usually supported by the non-neoplastic cells that create a conducive environment for transformation and progression to occur. Interleukin 33 (IL-33) functions as a dual activity cytokine as it is also a nuclear factor. IL-33 is usually present in the nuclei of the cells. Upon tissue damage, it is released into the extracellular space and binds to its receptor, suppression of tumorigenicity 2 (ST2) L, which is expressed on the membranes of the target cells. IL-33 signalling activates the T Helper 2 (Th2) immune response among other responses. Although the studies on the role of IL-33 in gastric cancer are still in the early stages, they have revealed potentially important (though sometimes conflicting) functions or roles in cancer development and progression. The pro-tumorigenic roles include induction and the recruitment of tumor-associated immune cells, promoting metaplasia progression, and inducing stem cell like and EMT properties in gastric cancer cells. Therapeutic interventions to disrupt these functions may provide a unique strategy for gastric cancer prevention and treatment. This review aims to provide a summary of the role of IL-33 in GC, state its multiple functions in relation to GC, and show potential avenues for promising therapeutic investigation.

MDSCs in breast cancer: an important enabler of tumor progression and an emerging therapeutic target

Women worldwide are more likely to develop breast cancer (BC) than any other type of cancer. The treatment of BC depends on the subtype and stage of the cancer, such as surgery, radiotherapy, chemotherapy, and immunotherapy. Although significant progress has been made in recent years, advanced or metastatic BC presents a poor prognosis, due to drug resistance and recurrences. During embryonic development, myeloid-derived suppressor cells (MDSCs) develop that suppress the immune system. By inhibiting anti-immune effects and promoting non-immune mechanisms such as tumor cell stemness, epithelial-mesenchymal transformation (EMT) and angiogenesis, MDSCs effectively promote tumor growth and metastasis. In various BC models, peripheral tissues, and tumor microenvironments (TME), MDSCs have been found to amplification. Clinical progression or poor prognosis are strongly associated with increased MDSCs. In this review, we describe the activation, recruitment, and differentiation of MDSCs production in BC, the involvement of MDSCs in BC progression, and the clinical characteristics of MDSCs as a potential BC therapy target.

Initial Myeloid Cell Status Is Associated with Clinical Outcomes of Renal Cell Carcinoma

The therapeutic outcome of immune checkpoint inhibition (ICI) can be improved through combination treatments with ICI therapy. Myeloid-derived suppressor cells (MDSCs) strongly suppress tumor immunity. MDSCs are a heterogeneous cell population, originating from the unusual differentiation of neutrophils/monocytes induced by environmental factors such as inflammation. The myeloid cell population consists of an indistinguishable mixture of various types of MDSCs and activated neutrophils/monocytes. In this study, we investigated whether the clinical outcomes of ICI therapy could be predicted by estimating the status of the myeloid cells, including MDSCs. Several MDSC indexes, such as glycosylphosphatidylinositol-anchored 80 kD protein (GPI-80), CD16, and latency-associated peptide-1 (LAP-1; transforming growth factor-β1 precursor), were analyzed via flow cytometry using peripheral blood derived from patients with advanced renal cell carcinoma (n = 51) immediately before and during the therapy. Elevated CD16 and LAP-1 expressions after the first treatment were associated with a poor response to ICI therapy. Immediately before ICI therapy, GPI-80 expression in neutrophils was significantly higher in patients with a complete response than in those with disease progression. This is the first study to demonstrate a relationship between the status of the myeloid cells during the initial phase of ICI therapy and clinical outcomes.

Transcriptomic analysis of esophageal cancer reveals hub genes and networks involved in cancer progression

Esophageal carcinoma (ESCA) has a 5-year survival rate of fewer than 20%. The study aimed to identify new predictive biomarkers for ESCA through transcriptomics meta-analysis to address the problems of ineffective cancer therapy, lack of efficient diagnostic tools, and costly screening and contribute to developing more efficient cancer screening and treatments by identifying new marker genes. Nine GEO datasets of three kinds of esophageal carcinoma were analyzed, and 20 differentially expressed genes were detected in carcinogenic pathways. Network analysis revealed four hub genes, namely RAR Related Orphan Receptor A (RORA), lysine acetyltransferase 2B (KAT2B), Cell Division Cycle 25B (CDC25B), and Epithelial Cell Transforming 2 (ECT2). Overexpression of RORA, KAT2B, and ECT2 was identified with a bad prognosis. These hub genes modulate immune cell infiltration. These hub genes modulate immune cell infiltration. Although this research needs lab confirmation, we found interesting biomarkers in ESCA that may aid in diagnosis and treatment.

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 mechanisms on evasion of anti-tumor immune responses in gastric cancer

The immune system and the tumor have been at each other's throats for so long that the neoplasm has learned to avoid detection and avoid being attacked, which is called immune evasion. Malignant tumors, such as gastric cancer (GC), share the ability to evade the body's immune system as a defining feature. Immune evasion includes alterations to tumor-associated antigens (TAAs), antigen presentation mechanisms (APMs), and the tumor microenvironment (TME). While TAA and APM are simpler in nature, they both involve mutations or epigenetic regulation of genes. The TME is comprised of numerous cell types, cytokines, chemokines and extracellular matrix, any one of which might be altered to have an effect on the surrounding ecosystem. The NF-kB, MAPK, PI3K/AKT, JAK/STAT, Wnt/β-catenin, Notch, Hippo and TGF-β/Smad signaling pathways are all associated with gastric cancer tumor immune evasion. In this review, we will delineate the functions of these pathways in immune evasion.

Dual Immune Regulatory Roles of Interleukin-33 in Pathological Conditions

Interleukin-33 (IL-33), a member of the IL-1 cytokine family and a multifunctional cytokine, plays critical roles in maintaining host homeostasis and in pathological conditions, such as allergy, infectious diseases, and cancer, by acting on multiple types of immune cells and promoting type 1 and 2 immune responses. IL-33 is rapidly released by immune and non-immune cells upon stimulation by stress, acting as an “alarmin” by binding to its receptor, suppression of tumorigenicity 2 (ST2), to trigger downstream signaling pathways and activate inflammatory and immune responses. It has been recognized that IL-33 displays dual-functioning immune regulatory effects in many diseases and has both pro- and anti-tumorigenic effects, likely depending on its primary target cells, IL-33/sST2 expression levels, cellular context, and the cytokine microenvironment. Herein, we summarize our current understanding of the biological functions of IL-33 and its roles in the pathogenesis of various conditions, including inflammatory and autoimmune diseases, infections, cancers, and cases of organ transplantation. We emphasize the nature of context-dependent dual immune regulatory functions of IL-33 in many cells and diseases and review systemic studies to understand the distinct roles of IL-33 in different cells, which is essential to the development of more effective diagnoses and therapeutic approaches for IL-33-related diseases.

Emerging roles for IL-25 and IL-33 in colorectal cancer tumorigenesis

Colorectal cancer (CRC) is the second leading cause of cancer-related death worldwide, and is largely refractory to current immunotherapeutic interventions. The lack of efficacy of existing cancer immunotherapies in CRC reflects the complex nature of the unique intestinal immune environment, which serves to maintain barrier integrity against pathogens and harmful environmental stimuli while sustaining host-microbe symbiosis during homeostasis. With their expression by barrier epithelial cells, the cytokines interleukin-25 (IL-25) and IL-33 play key roles in intestinal immune responses, and have been associated with inappropriate allergic reactions, autoimmune diseases and cancer pathology. Studies in the past decade have begun to uncover the important roles of IL-25 and IL-33 in shaping the CRC tumour immune microenvironment, where they may promote or inhibit tumorigenesis depending on the specific CRC subtype. Notably, both IL-25 and IL-33 have been shown to act on group 2 innate lymphoid cells (ILC2s), but can also stimulate an array of other innate and adaptive immune cell types. Though sometimes their functions can overlap they can also produce distinct phenotypes dependent on the differential distribution of their receptor expression. Furthermore, both IL-25 and IL-33 modulate pathways previously known to contribute to CRC tumorigenesis, including angiogenesis, tumour stemness, invasion and metastasis. Here, we review our current understanding of IL-25 and IL-33 in CRC tumorigenesis, with specific focus on dissecting their individual function in the context of distinct subtypes of CRC, and the potential prospects for targeting these pathways in CRC immunotherapy.

Interleukin-33: Metabolic checkpoints, metabolic processes, and epigenetic regulation in immune cells

Interleukin-33 (IL-33) is a pleiotropic cytokine linked to various immune cells in the innate and adaptive immune systems. Recent studies of the effects of IL-33 on immune cells are beginning to reveal its regulatory mechanisms at the levels of cellular metabolism and epigenetic modifications. In response to IL-33 stimulation, these programs are intertwined with transcriptional programs, ultimately determining the fate of immune cells. Understanding these specific molecular events will help to explain the complex role of IL-33 in immune cells, thereby guiding the development of new strategies for immune intervention. Here, we highlight recent findings that reveal how IL-33, acting as an intracellular nuclear factor or an extracellular cytokine, alters metabolic checkpoints and cellular metabolism, which coordinately contribute to cell growth and function. We also discuss recent studies supporting the role of IL-33 in epigenetic alterations and speculate about the mechanisms underlying this relationship.

IL-33 biology in cancer: An update and future perspectives

Interleukin-33 (IL-33) is a member of the IL-1 family of cytokines that is constitutively expressed in the nucleus of epithelial, endothelial and fibroblast-like cells. Upon cell stress, damage or necrosis, IL-33 is released into the cytoplasm to exert its prime role as an alarmin by binding to its specific receptor moiety, ST2. IL-33 exhibits pleiotropic function in inflammatory diseases and particularly in cancer. IL-33 may play a dual role as both a pro-tumorigenic and anti-tumorigenic cytokine, dependent on tumor and cellular context, expression levels, bioactivity and the nature of the inflammatory environment. In this review, we discuss the differential contribution of IL-33 to malignant or inflammatory conditions, its multifaceted effects on the tumor microenvironment, while providing possible explanations for the discrepant findings described in the literature. Additionally, we examine the emerging and divergent functions of IL-33 in the nucleus, and aspects of IL-33 biology that are currently under-addressed.

Possible Metastatic Stage-Dependent ILC2 Activation Induces Differential Functions of MDSCs through IL-13/IL-13Rα1 Signaling during the Progression of Breast Cancer Lung Metastasis

Simple Summary

When breast cancer metastasizes to the lung, group 2 innate lymphoid cells (ILC2s) are thought to promote tumor growth via the activation of myeloid-derived suppressor cells (MDSCs). In this study, we aimed to characterize the dynamic interactions of ILC2s and MDSCs during the course of cancer progression from the micrometastatic to the macrometastatic stages. We found that ILC2s were activated in both the micro- and macrometastatic regions, suggesting sustained activation throughout the metastatic cascades. In addition, our findings indicate that ILC2s may induce the immunosuppressive functions of MDSCs during the later stages of metastasis. Concomitantly, ILC2 may instigate extracellular matrix remodeling by polymorphonuclear (PMN)-MDSC activation during the early stages of metastasis. These metastatic-stage-specific changes may contribute to metastatic tumor growth in the microenvironment of breast cancer lung metastasis.

Abstract

Breast cancer is the most common cancer in women worldwide, and lung metastasis is one of the most frequent distant metastases. When breast cancer metastasizes to the lung, group 2 innate lymphoid cells (ILC2s) are thought to promote tumor growth via the activation of myeloid-derived suppressor cells (MDSCs), which are known to negatively regulate anticancer immune responses. However, it remains to be elucidated exactly how this ILC2–MDSC interaction is involved in tumor growth during metastases formation. Using a 4T1/LM4 breast cancer mouse model, we found that ILC2s were activated in both the micro- and macrometastatic regions, suggesting sustained activation throughout the metastatic cascades via IL-33/ST2 signaling. Consistent with IL-13 secretion from activated ILC2s, the frequencies of polymorphonuclear (PMN)- and monocytic (M)-MDSCs were also significantly elevated during the progression from micro- to macrometastatic cancer. However, the effects of ILC2-induced MDSC functionality on the microenvironment differed in a metastatic-stage-specific manner. Our findings indicate that ILC2s may induce the immunosuppressive functions of MDSCs during the later stages of metastasis. Concomitantly, ILC2 may instigate extracellular matrix remodeling by PMN-MDSC activation during the early stages of metastasis. These metastatic-stage-specific changes may contribute to metastatic tumor growth in the microenvironment of breast cancer lung metastasis.

Immunity and Breast Cancer: Focus on Eosinophils

The role of eosinophils, a cell type involved in the immune response to parasitic infections and allergies, has been investigated in different cancer types, in both tumor tissue and at the circulating level. Most studies showed a role mainly in conjunction with immunotherapy in melanomas and lung tumors, while few data are available in breast cancer. In this review, we summarize literature data on breast cancer, showing a prognostic role of circulating eosinophil counts as well as of the presence of tumor tissue infiltration by eosinophils. In particular, some studies showed an association between a higher circulating eosinophil count and a good prognosis, as well as an association with response to neoadjuvant chemotherapy in hormone receptor-negative/HER2-positive and in triple negative breast cancer. Several mechanistic studies have also been conducted in in vivo models, but the exact mechanism by which eosinophils act in the presence of breast cancer is still unknown. Further studies on this subject are desirable, in order to understand their role at the cellular level, identify related biomarkers and/or possibly search for new therapeutic targets.

The Janus Face of IL-33 Signaling in Tumor Development and Immune Escape

Simple Summary

Interleukin-33 (IL-33) is often released from damaged cells, acting as a danger signal. IL-33 exerts its function by interacting with its receptor suppression of tumorigenicity 2 (ST2) that is constitutively expressed on most immune cells. Therefore, IL-33/ST2 signaling can modulate immune responses to participate actively in a variety of pathological conditions, such as cancer. Like a two-faced Janus, which faces opposite directions, IL-33/ST2 signaling may play contradictory roles on its impact on cancer progression through both immune and nonimmune cellular components. Accumulating evidence demonstrates both pro- and anti-tumorigenic properties of IL-33, depending on the complex nature of different tumor immune microenvironments. We summarize and discuss the most recent studies on the contradictory effects of IL-33 on cancer progression and treatment, with a goal to better understanding the various ways for IL-33 as a therapeutic target.

Abstract

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, plays a critical role in maintaining tissue homeostasis as well as pathological conditions, such as allergy, infectious disease, and cancer, by promoting type 1 and 2 immune responses. Through its specific receptor ST2, IL-33 exerts multifaceted functions through the activation of diverse intracellular signaling pathways. ST2 is expressed in different types of immune cells, including Th2 cells, Th1 cells, CD8⁺ T cells, regulatory T cells (T_reg), cytotoxic NK cells, group 2 innate lymphoid cells (ILC2s), and myeloid cells. During cancer initiation and progression, the aberrant regulation of the IL-33/ST2 axis in the tumor microenvironment (TME) extrinsically and intrinsically mediates immune editing via modulation of both innate and adaptive immune cell components. The summarized results in this review suggest that IL-33 exerts dual-functioning, pro- as well as anti-tumorigenic effects depending on the tumor type, expression levels, cellular context, and cytokine milieu. A better understanding of the distinct roles of IL-33 in epithelial, stromal, and immune cell compartments will benefit the development of a targeting strategy for this IL-33/ST2 axis for cancer immunotherapy.

Soluble cluster of differentiation 14 levels elevated in bile from gallbladder cancer cases from Shanghai, China

Elevated systemic levels of soluble cluster of differentiation 14 (sCD14) have been associated with gallbladder cancer (GBC), but the association with sCD14 levels within the gallbladder has not been investigated. Here, we evaluated sCD14 in the bile of 41 GBC cases and 117 gallstone controls with data on 65 bile inflammation markers. We examined the relationship between bile sCD14 levels and GBC using logistic regression and stratified the analysis by stage. We included GBC-associated inflammatory biomarkers in the model to evaluate the influence of local inflammation. Bile sCD14 levels (third versus first tertile) were associated with GBC (adjusted odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.2–8.0). The association was equally strong for stage I/II (OR: 3.3, 95% CI: 0.9–15.6) and stage III/IV (OR: 3.2, 95% CI: 1.0–12.4) cancers. Including the GBC-associated inflammatory markers in the model removed the association between bile sCD14 and GBC (OR: 1.0, 95% CI: 0.3–3.5). The findings suggest that immune activation within the gallbladder may be related to GBC development, and the effect of sCD14 is influenced by inflammation. Similar associations across tumor stages suggest that elevated bile sCD14 levels may reflect changes early in GBC pathogenesis. Associations between GBC and sCD14 levels in both bile and plasma suggest sCD14 could be a potential biomarker for GBC.

IL-33/ST2 as a potential target for tumor immunotherapy

IL-33, a member of the IL-1 family, was initially reported to be expressed constitutively in the nucleus of tissue-lining and structural cells. However, upon tissue damage or injury, IL-33 can be released quickly to bind with its cognate receptor ST2 in response to wound healing and inflammation and act as a DAMP. As a key regulator of Th2 responses, IL-33/ST2 signal is primarily associated with immunity and immune-related disorders. In recent years, IL-33/ST2 signaling pathway has been reported to promote the development of cancer and remodel the tumor microenvironment by expanding immune suppressive cells such as myeloid-derived suppressor cells or regulatory T cells. However, its role remains controversial in some tumor settings. IL-33 could also promote effective infiltration of immune cells such as CD8⁺ T and NK cells, which act as antitumor. These dual effects may limit the clinical application to target this cytokine axis. Therefore, more comprehensive exploration and deeper understanding of IL-33 are required. In this review, we summarized the IL-33/ST2 axis versatile roles in the tumor microenvironment with a focus on the IL-33-target immune cells and downstream signaling pathways. We also discuss how the IL-33/ST2 axis could be used as a potential therapeutic target for cancer immunotherapy.

The MNK1/2-eIF4E Axis Supports Immune Suppression and Metastasis in Postpartum Breast Cancer

Breast cancer diagnosed within 10 years following childbirth is defined as postpartum breast cancer (PPBC) and is highly metastatic. Interactions between immune cells and other stromal cells within the involuting mammary gland are fundamental in facilitating an aggressive tumor phenotype. The MNK1/2-eIF4E axis promotes translation of prometastatic mRNAs in tumor cells, but its role in modulating the function of nontumor cells in the PPBC microenvironment has not been explored. Here, we used a combination of in vivo PPBC models and in vitro assays to study the effects of inactivation of the MNK1/2-eIF4E axis on the protumor function of select cells of the tumor microenvironment. PPBC mice deficient for phospho-eIF4E (eIF4E^S209A) were protected against lung metastasis and exhibited differences in the tumor and lung immune microenvironment compared with wild-type mice. Moreover, the expression of fibroblast-derived IL33, an alarmin known to induce invasion, was repressed upon MNK1/2-eIF4E axis inhibition. Imaging mass cytometry on PPBC and non-PPBC patient samples indicated that human PPBC contains phospho-eIF4E high-expressing tumor cells and CD8⁺ T cells displaying markers of an activated dysfunctional phenotype. Finally, inhibition of MNK1/2 combined with anti-PD-1 therapy blocked lung metastasis of PPBC. These findings implicate the involvement of the MNK1/2-eIF4E axis during PPBC metastasis and suggest a promising immunomodulatory route to enhance the efficacy of immunotherapy by blocking phospho-eIF4E. SIGNIFICANCE: This study investigates the MNK1/2-eIF4E signaling axis in tumor and stromal cells in metastatic breast cancer and reveals that MNK1/2 inhibition suppresses metastasis and sensitizes tumors to anti-PD-1 immunotherapy.

Elevated M-MDSCs in Circulation Are Indicative of Poor Prognosis in Diffuse Large B-Cell Lymphoma Patients

Myeloid-derived suppressor cells (MDSCs) are defined as negative regulators that suppress the immune response through a variety of mechanisms, which usually cluster in cancer, inflammation, and autoimmune diseases. This study aims to investigate the correlation between M-MDSCs and the clinical features of diffuse large B-cell lymphoma (DLBCL) patients, as well as the possible accumulation mechanism of M-MDSCs. The level of M-MDSCs is significantly increased in newly diagnosed and relapsed DLBCL patients. Regarding newly diagnosed DLBCL patients, the frequency of M-MDSCs is positively correlated with tumor progression and negatively correlated with overall survival (OS). More importantly, the level of M-MDSCs can be defined as a biomarker for a poor prognosis in DLBCL patients. Additionally, interleukin-35 (IL-35) mediates the accumulation of M-MDSCs in DLBCL patients. Anti-IL-35 treatment significantly reduces levels of M-MDSCs in Ly8 tumor-bearing mice. Thus, M-MDSCs are involved in the pathological process of DLBCL. Targeting M-MDSCs may be a promising therapeutic strategy for the treatment of DLBCL patients.

The diverse roles of myeloid derived suppressor cells in mucosal immunity

The mucosal immune system plays a vital role in protecting the host from the external environment. Its major challenge is to balance immune responses against harmful and harmless agents and serve as a 'homeostatic gate keeper'. Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of undifferentiated cells that are characterized by an immunoregulatory and immunosuppressive phenotype. Herein we postulate that MDSCs may be involved in shaping immune responses related to mucosal immunity, due to their immunomodulatory and tissue remodeling functions. Until recently, MDSCs were investigated mainly in cancerous diseases, where they induce and contribute to an immunosuppressive and inflammatory environment that favors tumor development. However, it is now becoming clear that MDSCs participate in non-cancerous conditions such as chronic infections, autoimmune diseases, pregnancy, aging processes and immune tolerance to commensal microbiota at mucosal sites. Since MDSCs are found in the periphery only in small numbers under normal conditions, their role is highlighted during pathologies characterized by acute or chronic inflammation, when they accumulate and become activated. In this review, we describe several aspects of the current knowledge characterizing MDSCs and their involvement in the regulation of the mucosal epithelial barrier, their crosstalk with commensal microbiota and pathogenic microorganisms, and their complex interactions with a variety of surrounding regulatory and effector immune cells. Finally, we discuss the beneficial and harmful outcomes of the MDSC regulatory functions in diseases affecting mucosal tissues. We wish to illuminate the pivotal role of MDSCs in mucosal immunity, the limitations in our understanding of all the players and the intricate challenges stemming from the complex interactions of MDSCs with their environment.

Umbilical cord mesenchymal stem cells enhance the therapeutic effect of imipenem by regulating myeloid-derived suppressor cells in septic mice

Background

Umbilical cord mesenchymal stem cells (UC-MSCs), which possess potent immunomodulatory effects and low immunogenicity, are considered to be a promising stem cell-based therapy for sepsis. In the current study, we aimed to investigate whether the combined use of UC-MSCs and imipenem has a better effect than imipenem alone in treating Escherichia coli (E. coli)-induced sepsis and to explore the mechanism by which UC-MSCs exert their therapeutic effect in septic mice.

Methods

We randomly divided mice into five groups with 10 mice in each group: the normal control group (control group), the sepsis group (vehicle group), the MSCs treatment group (MSCs group), the imipenem treatment group (imipenem group), and the imipenem plus MSCs treatment group (imipenem + MSCs group). We monitored the survival rate in each group every 12 h for 3 days. After observing the survival rate, another 50 mice were also randomly divided into five groups, and the mice were sacrificed after 24 h. Bacterial colonies from the blood and peritoneal lavage fluid were counted in a blinded manner. Organ injury was analyzed by hematoxylin and eosin (HE) staining. Frequencies of myeloid-derived suppressor cells (MDSCs) in the blood, spleen, and bone marrow (BM) were determined by flow cytometry. Plasma levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-1β, and IL-10 were detected by enzyme-linked immunosorbent assay (ELISA).

Results

Compared with imipenem treatment, the co-administration of UC-MSCs and imipenem dramatically improved the survival rate, decreased the bacterial load, and ameliorated organ injury. Furthermore, UC-MSCs treatment, either alone or in combination with imipenem, significantly increased plasma levels of IL-10 and the percentage of MDSCs by inducing arginase-1 in septic mice.

Conclusions

Our results indicated that UC-MSCs protect mice against sepsis by acting on MDSCs. Combination therapy of UC-MSCs and imipenem may be a new approach for the future clinical treatment of sepsis.

Cargo-free immunomodulatory nanoparticles combined with anti-PD-1 antibody for treating metastatic breast cancer

The presence of immunosuppressive innate immune cells such as myeloid derived suppressor cells (MDSCs), Ly6C-high monocytes, and tumor-associated macrophages (TAMs) at a tumor can inhibit effector T cell and NK cell function. Immune checkpoint blockade using anti-PD-1 antibody aims to overcome the immune suppressive environment, yet only a fraction of patients responds. Herein, we test the hypothesis that cargo-free PLG nanoparticles administered intravenously can divert circulating immune cells from the tumor microenvironment to enhance the efficacy of anti-PD-1 immunotherapy in the 4T1 mouse model of metastatic triple-negative breast cancer. In vitro studies demonstrate that these nanoparticles decrease the expression of MCP-1 by 5-fold and increase the expression of TNF-α by more than 2-fold upon uptake by innate immune cells. Intravenous administration of particles results in internalization by MDSCs and monocytes, with particles detected in the liver, lung, spleen, and primary tumor. Nanoparticle delivery decreased the abundance of MDSCs in circulation and in the lung, the latter being the primary metastatic site. Combined with anti-PD-1 antibody, nanoparticles significantly slowed tumor growth and resulted in a survival benefit. Gene expression analysis by GSEA indicated inflammatory myeloid cell pathways were downregulated in the lung and upregulated in the spleen and tumor. Upregulation of extrinsic apoptotic pathways was also observed in the primary tumor. Collectively, these results demonstrate that cargo-free PLG nanoparticles can reprogram immune cell responses and alter the tumor microenvironment in vivo to overcome the local immune suppression attributed to myeloid cells and enhance the efficacy of anti-PD-1 therapy.

Interleukin-33 Promotes Cell Survival via p38 MAPK-Mediated Interleukin-6 Gene Expression and Release in Pediatric AML

Acute myeloid leukemia (AML) is a fatal disease characterized by the accumulation of immature myeloid blasts in the bone marrow (BM). Cytokine provide signals for leukemia cells to improve their survival in the BM microenvironment. Previously, we identified interleukin-33 (IL-33) as a promoter of cell survival in a human AML cell line and primary mouse leukemia cells. In this study, we report that the cell surface expression of IL-33–specific receptor, Interleukin 1 Receptor Like 1 (IL1RL1), is elevated in BM cells from AML patients at diagnosis, and the serum level of IL-33 in AML patients is higher than that of healthy donor controls. Moreover, IL-33 levels are found to be positively associated with IL-6 levels in pediatric patients with AML. In vitro, IL-33 treatment increased IL-6 mRNA expression and protein level in BM and peripheral blood (PB) cells from AML patients. Evidence was also provided that IL-33 inhibits cell apoptosis by activating p38 mitogen-activated protein kinase (MAPK) pathway using human AML cell line and AML patient samples. Finally, we confirmed that IL-33 activated IL-6 expression in a manner that required p38 MAPK pathway using clinical AML samples. Taken together, we identified a potential mechanism of IL-33–mediated survival involving p38 MAPK in pediatric AML patients that would facilitate future drug development.

The Contradictory Role of Interleukin-33 in Immune Cells and Tumor Immunity

Interleukin (IL)-33 is a member of the IL-1 superfamily and is a crucial cytokine playing the role of a dual-function molecule. IL-33 mediates its function by interacting with its receptor suppression of tumorigenicity 2 (ST2), which is constitutively expressed on T helper (Th)1 cells, Th2 cells, and other immune cells. Previously, we summarized findings on IL-33 and performed an intensive study of the correlation between IL-33 and tumor. IL-33 enables anti-tumor immune responses through Th1 cells and natural killer (NK) cells and plays a role in tumor immune escape in cancers via Th2 cells and regulatory T cells. Herein, we discuss the contradictory role of IL-33 in immune cells in different cancer, and our summaries may be helpful for better understanding of the development of research on IL-33 and tumor immunity.

Mechanisms of Maintenance of Foot-and-Mouth Disease Virus Persistence Inferred From Genes Differentially Expressed in Nasopharyngeal Epithelia of Virus Carriers and Non-carriers

Foot-and-mouth disease virus (FMDV) causes persistent infection of nasopharyngeal epithelial cells in ~50% of infected ruminants. The mechanisms involved are not clear. This study provides a continued investigation of differentially expressed genes (DEG) identified in a previously published transcriptomic study analyzing micro-dissected epithelial samples from FMDV carriers and non-carriers. Pathway analysis of DEG indicated that immune cell trafficking, cell death and hematological system could be affected by the differential gene expression. Further examination of the DEG identified five downregulated (chemerin, CCL23, CXCL15, CXCL16, and CXCL17) and one upregulated (CCL2) chemokines in carriers compared to non-carriers. The differential expression could reduce the recruitment of neutrophils, antigen-experienced T cells and dendritic cells and increase the migration of macrophages and NK cells to the epithelia in carriers, which was supported by DEG expressed in these immune cells. Downregulated chemokine expression could be mainly due to the inhibition of canonical NFκB signaling based on DEG in the signaling pathways and transcription factor binding sites predicted from the proximal promoters. Additionally, upregulated CD69, IL33, and NID1 and downregulated CASP3, IL17RA, NCR3LG1, TP53BP1, TRAF3, and TRAF6 in carriers could inhibit the Th17 response, NK cell cytotoxicity and apoptosis. Based on our findings, we hypothesize that (1) under-expression of chemokines that recruit neutrophils, antigen-experienced T cells and dendritic cells, (2) blocking NK cell binding to target cells and (3) suppression of apoptosis induced by death receptor signaling, viral RNA, and cell-mediated cytotoxicity in the epithelia compromised virus clearance and allowed FMDV to persist. These hypothesized mechanisms provide novel information for further investigation of persistent FMDV infection.

Blood eosinophilic relative count is prognostic for breast cancer and associated with the presence of tumor at diagnosis and at time of relapse

Background

Cancer outcome is associated with circulating immune cells, including eosinophils. Here we analyze the relative eosinophil count (REC) in different breast cancer subtypes.

Methods

Stage I–III breast cancer patients were included in the study and classified as REC-high vs low (cutoff 1.5%) or relative lymphocyte count (RLC)-high vs low (cutoff 17.5%). The co-primary endpoints were the breast cancer-specific survival (BCSS) or the time to treatment failure (TTF) in the REC groups.

Results

Overall 930 patients were included in the study. We observed a benefit for REC-high vs REC-low in TTF (HR 0.610, 95% CI 0.458–0.812), and in BCSS (HR 0.632, 95% CI 0.433–0.923). Similarly, we observed a better TTF (HR 0.421, 95% CI 0.262–0.677) and BCSS (HR 0.350, 95% CI 0.200–0.614) in RLC-high vs low. A lower relapse rate was observed in the REC-high vs REC-low group (17.1% vs 24.7%, p = 0.005), not confirmed in the multivariate analysis. A lower median REC at baseline and at relapse was observed compared to REC after surgery and during cancer-free follow-up (p < .0001).

Conclusions

REC could be a new promising, affordable and accessible predictive and prognostic biomarker in all breast cancer subtypes.

The IL-33/ST2 pathway suppresses murine colon cancer growth and metastasis by upregulating CD40 L signaling

Interleukin (IL)-33 is a member of the IL-1 family, participating in both helper T1 (Th1)- and Th2-type immune responses, but its ambiguous effects on tumor growth and related immune mechanisms remain unclear. Here, we report that recombinant mouse IL-33 (mIL-33) significantly inhibited colon cancer growth and metastasis to lung and liver in a murine CT26 or MC38 tumor-cell engraftment model. This effect could be associated with CD4⁺ T cells and CD40 L signaling, as depletion of CD4⁺ T cells or blocking CD40 L signaling in vivo partly abolished the antitumor function of IL-33. In addition, IL-33 treatment upregulated CD40 L expression on tumor-infiltrating lymphocytes, and promoted the activation of CD4⁺ T, CD8⁺ T and natural killer cells via CD40 L signaling. Furthermore, IL-33 was sufficient to induce the ST2 expression on CD4⁺ T cells, but not on CD8⁺ T and natural killer cells, indicating that IL-33 acted on CD4⁺ T cells via a positive-feedback loop. Our findings shed new light on the IL-33-mediated antitumor effects and mechanisms of Th1 action, and also suggest that IL-33 may serve as an activator to boost anticancer immune responses in singular or combinatory therapies.

The IL-33/ST2 Axis in Immune Responses Against Parasitic Disease: Potential Therapeutic Applications

Parasitic infections pose a wide and varying threat globally, impacting over 25% of the global population with many more at risk of infection. These infections are comprised of, but not limited to, toxoplasmosis, malaria, leishmaniasis and any one of a wide variety of helminthic infections. While a great deal is understood about the adaptive immune response to each of these parasites, there remains a need to further elucidate the early innate immune response. Interleukin-33 is being revealed as one of the earliest players in the cytokine milieu responding to parasitic invasion, and as such has been given the name "alarmin." A nuclear cytokine, interleukin-33 is housed primarily within epithelial and fibroblastic tissues and is released upon cellular damage or death. Evidence has shown that interleukin-33 seems to play a crucial role in priming the immune system toward a strong T helper type 2 immune response, necessary in the clearance of some parasites, while disease exacerbating in the context of others. With the possibility of being a double-edged sword, a great deal remains to be seen in how interleukin-33 and its receptor ST2 are involved in the immune response different parasites elicit, and how those parasites may manipulate or evade this host mechanism. In this review article we compile the current cutting-edge research into the interleukin-33 response to toxoplasmosis, malaria, leishmania, and helminthic infection. Furthermore, we provide insight into directions interleukin-33 research may take in the future, potential immunotherapeutic applications of interleukin-33 modulation and how a better clarity of early innate immune system responses involving interleukin-33/ST2 signaling may be applied in development of much needed treatment options against parasitic invaders.

Interleukin-33 pretreatment promotes metastatic growth of murine melanoma by reducing the cytotoxic capacity of CD8+ T cells and enhancing regulatory T cells

Interleukin-33 (IL-33) regulates innate and acquired immune response to pathogens, self-antigens and tumors. IL-33 effects on tumors depend on the dose and mode of administration along with the type of malignancy. We studied the effects of IL-33 on the development of primary and metastatic melanoma induced by B16-F1 cell line in C57BL/6 mice. Intraperitoneally applied IL-33 restricts primary tumor growth. When administered intranasally 3 days prior to the intravenous injection of the tumor cells, IL-33 promoted growth of B16-F1 melanoma metastases, while B16-F10 gave massive metastases independently of IL-33. To mimic natural dissemination, we next used a limited number (5 × 10⁴) of B16-F1 cells intravenously followed by application of IL-33 intraperitoneally. IL-33 increased the size of metastases (10.96 ± 3.96 mm²) when compared to the control group (0.86 ± 0.39 mm²), without changing incidence and number of metastases. IL-33 increased expression of ST2 on both tumor and immune cells in metastases. Also, IL-33 enhanced eosinophils and anti-tumor NK cells in the lung. The striking finding was reduced cytotoxicity of CD8⁺ T cells derived from metastatic lung of IL-33 injected mice. IL-33 reduced the percentage of TNF-α⁺ and IFN-γ⁺ CD8⁺ T cells while increasing the frequency of CD8⁺ T cells that express inhibitory molecules (PD-1, KLRG-1 and CTLA-4). There was a significant accumulation of CD11b⁺Gr-1⁺ myeloid suppressor cells and FoxP3⁺, IL-10⁺ and CTLA-4⁺ regulatory T cells in the metastatic lung of IL-33 injected mice. The relevance of IL-33 for melanoma metastases was also documented in a significantly increased level of serum IL-33 in stage III melanoma patients.

Green Tea Polyphenol EGCG Attenuates MDSCs-mediated Immunosuppression through Canonical and Non-Canonical Pathways in a 4T1 Murine Breast Cancer Model

Several studies in the past decades have reported anti-tumor activity of the bioactive compounds extracted from tea leaves, with a focus on the compound epigallocatechin-3-gallate (EGCG). However, further investigations are required to unravel the underlying mechanisms behind the anti-tumor activity of EGCG. In this study, we demonstrate that EGCG significantly inhibits the growth of 4T1 breast cancer cells in vitro and in vivo. EGCG ameliorated immunosuppression by significantly decreasing the accumulation of myeloid-derived suppressor cells (MDSCs) and increasing the proportions of CD4⁺ and CD8⁺ T cells in spleen and tumor sites in 4T1 breast tumor-bearing mice. Surprisingly, a low dose of EGCG (0.5-5 μg/mL) effectively reduced the cell viability and increased the apoptosis rate of MDSCs in vitro. EGCG down-regulated the canonical pathways in MDSCs, mainly through the Arg-1/iNOS/Nox2/NF-κB/STAT3 signaling pathway. Moreover, transcriptomic analysis suggested that EGCG also affected the non-canonical pathways in MDSCs, such as ECM-receptor interaction and focal adhesion. qRT-PCR further validated that EGCG restored nine key genes in MDSCs, including Cxcl3, Vcan, Col4a1, Col8a1, Oasl2, Mmp12, Met, Itsnl and Acot1. Our results provide new insight into the mechanism of EGCG-associated key pathways/genes in MDSCs in the murine breast tumor model.

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.

LncRNAs regulate metabolism in cancer

Metabolic reprogramming is a hallmark of cancer. Mammalian genome is characterized by pervasive transcription, generating abundant non-coding RNAs (ncRNAs). Long non-coding RNAs (lncRNAs) are freshly discovered functional ncRNAs exerting extensive regulatory impact through diverse mechanisms. Emerging studies have revealed widespread roles of lncRNAs in the regulation of various cellular activities, including metabolic pathways. In this review, we summarize the latest advances regarding the regulatory roles of lncRNAs in cancer metabolism, particularly their roles in mitochondrial function, glucose, glutamine, and lipid metabolism. Moreover, we discuss the clinical application and challenges of targeting lncRNAs in cancer metabolism. Understanding the complex and special behavior of lncRNAs will allow a better depiction of cancer metabolic networks and permit the development of lncRNA-based clinical therapies by targeting cancer metabolism.

ST2 Signaling in the Tumor Microenvironment

Suppression of tumorigenicity 2 (ST2), also known as interleukin-1 receptor-like 1 (IL1RL1), is one of the natural receptors of IL-33. Three major isoforms, ST2L (transmembrane form), sST2 (soluble form), and ST2V, are generated by alternative splicing. Damage to stromal cells induces necrosis and release of IL-33, which binds to heterodimeric ST2L/IL-1RAcP complex on the membrane of a variety of immune cells. This IL-33/ST2L signal induces transcription of the downstream inflammatory and anti-inflammatory genes by activating diverse intracellular kinases and factors to mount an adequate immune response, even in tumor microenvironment. For example, activation of IL-33/ST2L signal may trigger Th2-dependent M2 macrophage polarization to facilitate tumor progression. Notably, sST2 is a soluble form of ST2 that lacks a transmembrane domain but preserves an extracellular domain similar to ST2L, which acts as a "decoy" receptor for IL-33. sST2 has been shown to involve in the inflammatory tumor microenvironment and the progression of colorectal cancer, non-small cell lung cancer, and gastric cancer. Therefore, targeting the IL-33/ST2 axis becomes a promising new immunotherapy for treatment of many cancers. This chapter reviews the recent findings on IL-33/ST2L signaling in tumor microenvironment, the trafficking mode of sST2, and the pharmacological strategies to target IL-33/ST2 axis for cancer treatment.

Interleukin-33 activates and recruits natural killer cells to inhibit pulmonary metastatic cancer development

Increasing evidence suggests that IL-33 plays an important role in regulating tumor development. However, conflicting results, obtained from numerous studies, have highlighted the divergent functions of IL-33. The detailed mechanisms by which IL-33 modulates tumor development merit further investigation. Here, we report that IL-33 administration can effectively inhibit the development of pulmonary metastasis of breast cancer in a mouse. In our model, IL-33 promotes the production of TNF-α by macrophages, which increases IL-33 specific receptor (ST2) expression on natural killer (NK) cells and is pivotal in IL-33-induced NK cell activation. IL-33 treatment also facilitates the production of CCL5 in the lung by eosinophils and CD8⁺ T cells, which mediates the recruitment of NK cells to the tumor microenvironment. The systemic activation and local recruitment of NK cells result in potent tumor rejection in the lung. Our study reports a novel mechanism for the IL-33-meditated suppression of metastatic cancer and provides potential therapeutic strategies for targeting metastatic tumor.

Recombinant virus-like particles presenting IL-33 successfully modify the tumor microenvironment and facilitate antitumor immunity in a model of breast cancer

Recently, interleukin (IL)-33 has been closely associated with a variety of clinical cancers. IL-33 presents both protumorigenic, and less frequently, antitumorigenic functions depending on disease conditions. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. This study aimed to develop an effective approach to intervene in IL-33 functioning in tumors and reveal the immunotherapeutic potential of anti-IL-33 active immunization. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth in the preventive study and lung metastasis in both studies. The underlying mechanisms might include promoting tumor-specific Th1 and CTL-mediated cellular responses and the expression of the effector molecule interferon-γ (IFN-γ), suppressing T-helper type 2 (Th2) responses, and significantly reducing the infiltration of immunosuppressive Treg (regulatory T) cells and myeloid-derived suppressor cells (MDSCs) into tumor tissues in the immunized mice. In conclusion, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating the potential of this approach as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role. STATEMENT OF SIGNIFICANCE: Interleukin (IL)-33 is closely associated with a variety of clinical cancers. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth and lung metastasis in both studies. Furthermore, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating its potential as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role.

Tumor Characterization in Breast Cancer Identifies Immune-Relevant Gene Signatures Associated With Prognosis

There has been increasing attention on immune-oncology for its impressive clinical benefits in many different malignancies. However, due to molecular and genetic heterogeneity of tumors, the activities of traditional clinical and pathological criteria are far from satisfactory. Immune-based strategies have re-ignited hopes for the treatment and prevention of breast cancer. Prognostic or predictive biomarkers, associated with tumor immune microenvironment, may have great prospects in guiding patient management, identifying new immune-related molecular markers, establishing personalized risk assessment of breast cancer. Therefore, in this study, weighted gene co-expression network analysis (WGCNA), single-sample gene set enrichment analysis (ssGSEA), multivariate COX analysis, least absolute shrinkage, and selection operator (LASSO), and support vector machine-recursive feature elimination (SVM-RFE) algorithm, along with a series of analyses were performed, and four immune-related genes (APOD, CXCL14, IL33, and LIFR) were identified as biomarkers correlated with breast cancer prognosis. The findings may provide different insights into prognostic monitoring of immune-related targets for breast cancer or can be served as reference for the further research and validation of biomarkers.

The ST2/Interleukin-33 Axis in Hematologic Malignancies: The IL-33 Paradox

Interleukin (IL)-33 is a chromatin-related nuclear interleukin that is a component of IL-1 family. IL-33 production augments the course of inflammation after cell damage or death. It is discharged into the extracellular space. IL-33 is regarded as an “alarmin” able to stimulate several effectors of the immune system, regulating numerous immune responses comprising cancer immune reactions. IL-33 has been demonstrated to influence tumorigenesis. However, as far as this cytokine is concerned, we are faced with what has sometimes been defined as the IL-33 paradox. Several studies have demonstrated a relevant role of IL-33 to numerous malignancies, where it may have pro- and—less frequently—antitumorigenic actions. In the field of hematological malignancies, the role of IL-33 seems even more complex. Although we can affirm the existence of a negative role of IL-33 in Chronic myelogenos leukemia (CML) and in lymphoproliferative diseases and a positive role in pathologies such as Acute myeloid leukemia (AML), the action of IL-33 seems to be multiple and sometimes contradictory within the same pathology. In the future, we will have to learn to govern the negative aspects of activating the IL-33/ST2 axis and exploit the positive ones.

Next Generation Techniques for Determination of Protein-Protein Interactions: Beyond the Crystal Structure

PURPOSE OF REVIEW

We discuss recent advancements in structural biology methods for investigating sites of protein-protein interactions. We will inform readers outside the field of structural biology about techniques beyond crystallography, and how these different technologies can be utilized for drug development.

RECENT FINDINGS

Advancements in cryo-electron microscopy (cryoEM) and micro-electron diffraction (microED) may change how we view atomic resolution structural biology, such that well-ordered macrocrystals of protein complexes are not required for interface identification. However, some drug discovery applications, such as lead peptide compound generation, may not require atomic resolution; mass spectrometry techniques can provide an expedited path to generation of lead compounds. New crosslinking compounds, more user-friendly data analysis, and novel protocols such as protein painting can advance drug discovery programs, even in the absence of atomic resolution structural data. Finally, artificial intelligence and machine learning methods, while never truly replacing experimental methods, may provide rational ways to stratify potential druggable regions identified with mass spectrometry into higher and lower priority candidates.

SUMMARY

Electron diffraction of nanocrystals combines the benefits of both x-ray diffraction and cryoEM, and may prove to be the next generation of atomic resolution protein-protein interface identification. However, in situations such as peptide drug discovery, mass spectrometry techniques supported by advancements in computational methods will likely prove sufficient to support drug discovery efforts. In addition, these methods can be significantly faster than any crystallographic or cryoEM methods for identification of interacting regions.

Synergism of PDL/PD1 and IL33/ST2 Axis in Tumor Immunology

When it comes to tumor immunology, understanding of molecular pathways is rather important. During oncogenesis, many molecules should be taken in consideration altogether in context of a single malignancy. It is of a great significance to determine whether these molecules act synergistically or contrary, whether to understand a malignant disease more thoroughly, or even more important, to reveal new approaches of therapy. In this review, we discuss whether and how IL-33/ST2 and PD-1/PDL axis involve in antitumor immunity.