Overexpression of interleukin-33 is associated with poor prognosis of patients with glioma

Statin prevents cancer development in chronic inflammation by blocking interleukin 33 expression

Chronic inflammation is a major cause of cancer worldwide. Interleukin 33 (IL-33) is a critical initiator of cancer-prone chronic inflammation; however, its induction mechanism by environmental causes of chronic inflammation is unknown. Herein, we demonstrate that Toll-like receptor (TLR)3/4-TBK1-IRF3 pathway activation links environmental insults to IL-33 induction in the skin and pancreas inflammation. An FDA-approved drug library screen identifies pitavastatin to effectively suppress IL-33 expression by blocking TBK1 membrane recruitment/activation through the mevalonate pathway inhibition. Accordingly, pitavastatin prevents chronic pancreatitis and its cancer sequela in an IL-33-dependent manner. The IRF3-IL-33 axis is highly active in chronic pancreatitis and its associated pancreatic cancer in humans. Interestingly, pitavastatin use correlates with a significantly reduced risk of chronic pancreatitis and pancreatic cancer in patients. Our findings demonstrate that blocking the TBK1-IRF3-IL-33 signaling axis suppresses cancer-prone chronic inflammation. Statins present a safe and effective prophylactic strategy to prevent chronic inflammation and its cancer sequela.

Dexamethasone Suppresses IL-33-exacerbated Malignant Phenotype of U87MG Glioblastoma Cells via NF-κB and MAPK Signaling Pathways

BACKGROUND

Interleukin (IL)-33 is highly expressed in glioblastoma (GBM) and promotes tumor progression. Targeting IL-33 may be an effective strategy for the treatment of GBM. Dexamethasone (DEX) is a controversial drug routinely used clinically in GBM therapy. Whether DEX has an effect on IL-33 is unknown. This study aimed to investigate the effect of DEX on IL-33 and the molecular mechanisms involved.

METHODS

U87MG cells were induced by tumor necrosis factor (TNF)-α to express IL-33 and then treated with DEX. The mRNA levels of IL-33, NF-κB p65, ERK1/2, and p38 were determined by real-time quantitative PCR. The expression of IL-33, IkBα (a specific inhibitor of NF-κB) and MKP-1 (a negative regulator of MAPK), as well as the phosphorylation of NF-κB, ERK1/2 and p38 MAPK, were detected by Western blotting. The secretion of IL-33 was measured by ELISA. The proliferation, migration and invasion of U87MG cells were detected by CCK8 and transwell assays, respectively.

RESULTS

DEX significantly reduced TNF-α-induced production of IL-33 in U87MG cells, which was dependent on inhibiting the activation of the NF-κB, ERK1/2 and p38 MAPK signaling pathways, and was accompanied by the increased expression of IkBα but not MKP-1. Furthermore, the proliferation, migration and invasion of U87MG cells exacerbated by IL-33 were suppressed by DEX.

CONCLUSION

DEX inhibited the production and tumor-promoting function of IL-33. Whether DEX can benefit GBM patients remains controversial. Our results suggest that GBM patients with high IL-33 expression may benefit from DEX treatment and deserve further investigation.

The association of serum IL-33/ST2 expression with hepatocellular carcinoma

BACKGROUND

IL-33 is a multifunctional cytokine with dual functions. However, the clinicopathological and prognostic significance of IL-33 in cancer patients, especially in patients with hepatocellular carcinoma (HCC), remains controversial. Therefore, we conducted a study of 565 patients with HCC and 561 healthy controls and performed a meta-analysis to quantitatively evaluate the above problems.

METHODS

We collected blood from 565 patients with HCC and 561 healthy controls. ELISA was used to detect the concentrations of IL-33 and ST2 in the serum, and RT‒PCR was used to detect the levels of IL-33 and ST2 mRNA. Meanwhile, we collected comprehensive literature on IL-33 and the clinical characteristics of cancer patients retrieved from the PubMed, Web of Science and CNKI databases as of December 2022. An odds ratio (OR) with a 95% confidence interval (CI) was used to estimate the impact through overall and stratified analyses.

RESULTS

Compared with the healthy control group, the levels of ST2 mRNA and serum in the peripheral blood of HCC patients increased (p < 0.05), while the levels of IL-33 mRNA and serum showed no significant difference between the two groups (p > 0.05). In the meta-analysis section, at the tissue level, the overall analysis showed that the expression of IL-33 was positively correlated with tumor stage, histological grade, distant metastasis, and tumor size. Compared with patients with low IL-33 expression, the 3-year overall survival (OS) rate (OR = 3.467, p < 0.001) and 5-year OS rate (OR = 2.784, p < 0.001) of patients with high IL-33 expression were lower. At the serum expression level, the overall analysis showed that the expression of IL-33 increased the risk of cancer, and the serum level of IL-33 was positively correlated with tumor stage and vascular invasion.

CONCLUSION

IL-33/ST2 is a useful predictive or prognostic biomarker in clinical evaluation and may be used as a potential therapeutic target, but much research is needed to verify this hypothesis.

Commentary: Evaluating potential glioma serum biomarkers, with future applications

Systemic inflammation within malignant glioma is a topic of ongoing significance. In this commentary, we highlight recent findings from Gandhi et al and discuss alternative approaches. We present a counter argument with findings that IL-6 markers are controversial. We highlight the potential benefit of looking at microRNAs and other biomarkers. Finally, we present ideas for future application involving differentiation between radiation necrosis and recurrence. The commentary is intended to serve as a catalyst for further scientific discovery.

NCAPG Promotes Tumor Progression and Modulates Immune Cell Infiltration in Glioma

Glioma is one of the most deadly types of brain cancer. As it is highly invasive, the prognosis for glioma patients remains dismal, with median survival rarely exceeding 16 months. Thus, developing a new prognostic biomarker for glioma and investigating its molecular mechanisms is necessary for the development of an efficient treatment strategy. In this study, we analyzed a cohort of 1,131 glioma patients using RNA-seq data from The Cancer Genome Atlas (TCGA project) and Gene Expression Omnibus (GSE4290 and GSE16011 datasets), and validated the results using the RNA-seq data of 1,018 gliomas from the Chinese Glioma Genome Atlas (CGGA project). We used the R language as the main tool for statistical analysis and data visualization. We found that NCAPG, a mitosis-associated chromosomal condensing protein, is highly expressed in glioma tissues. Furthermore, the expression of NCAPG increased significantly with the increase in tumor grade, and high NCAPG expression was found to be a predictor of poor overall survival in glioma patients (P < 0.001). This result shows that NCAPG expression could be an independent prognostic factor. Importantly, when the expression of NCAPG was knocked down, the CCK-8 assay revealed that the proliferation of glioma cells (LN-229 and T98G cell lines) decreased significantly compared with the control group. In addition, the healing rates of these cells were significantly lower in the si-NCAPG group than in the control group (P < 0.001). We then used the CIBERSORT algorithm to analyze the expression levels of 22 subpopulations of immune cells and found that NCAPG was significantly negatively correlated with natural killer cell activation. In addition, it was positively correlated with MHC-I molecules and ADAM17. Our study is first in comprehensively describing the high expression of NCAPG in glioma. It also shows that NCAPG can function as an independent prognostic predictor of glioma, and that targeting NCAPG can be a new strategy for the treatment of glioma patients.

Targeting the Epithelium-Derived Innate Cytokines: From Bench to Bedside

When epithelial cells are exposed to potentially threatening external stimuli such as allergens, bacteria, viruses, and helminths, they instantly produce "alarmin" cytokines, namely, IL-33, IL-25, and TSLP. These alarmins alert the immune system about these threats, thereby mobilizing host immune defense mechanisms. Specifically, the alarmins strongly stimulate type-2 immune cells, including eosinophils, mast cells, dendritic cells, type-2 helper T cells, and type-2 innate lymphoid cells. Given that the alarm-raising role of IL-33, IL-25, and TSLP was first detected in allergic and infectious diseases, most studies on alarmins focus on their role in these diseases. However, recent studies suggest that alarmins also have a broad range of effector functions in other pathological conditions, including psoriasis, multiple sclerosis, and cancer. Therefore, this review provides an update on the epithelium-derived cytokines in both allergic and non-allergic diseases. We also review the progress of clinical trials on biological agents that target the alarmins and discuss the therapeutic potential of these agents in non-allergic diseases.

IL-33 induces ADAMTS5 expression and cell migration in glioblastoma multiforme

Glioblastoma multiforme (GBM), characterized by a high rate of proliferation and migration capacity, is an incurable brain tumor in adults. Interleukin-33 (IL-33), a member of the IL-1 cytokine superfamily, and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), a family of zinc dependent metalloproteinases, are known to have essential roles in GBM migration and invasion. Previous studies have separately revealed elevated expressions of IL-33 and ADAMTS5 in GBM; however, the interaction between IL-33 and ADAMTS5 in GBM remains unclear. Here, using publically available GlioVis and GEPIA programs, we showed that mRNA expressions of IL-33 and ADAMTS5 are significantly high in GBM cells, and a positive correlation between IL-33 and ADAMTS5 was also determined in these cells. In parallel with the mRNA data of IL-33 and ADAMTS5, by Western blot analysis, protein levels were found to be elevated in GBM tissues and increased gradually with the disease progression. Primary GBM cells and low-grade glioma cells were then treated with IL-33 to examine its stimulating effect on ADAMTS5 expression. Exposure to IL-33 raised ADAMTS5 protein levels in a dose-dependent manner. Finally, the wound-healing method was performed to confirm the impact of IL-33 on migration in primary GBM cells. IL-33 promoted migration of primary GBM cells three times higher than untreated GBM cells. Thus, the current study suggests for the first time that IL-33 might have a role in playing a part in GBM progression through induction of ADAMTS5 expression and promotion of migration in GBM cells.

An affinity for brainstem microglia in pediatric high-grade gliomas of brainstem origin

Background

High-grade gliomas (HGG) in children have a devastating prognosis and occur in a remarkable spatiotemporal pattern. Diffuse midline gliomas (DMG), including diffuse intrinsic pontine gliomas (DIPG), typically occur in mid-childhood, while cortical HGGs are more frequent in older children and adults. The mechanisms behind this pattern are not clear.

Methods

We used mouse organotypic slice cultures and glial cell cultures to test the impact of the microenvironment on human DIPG cells. Comparing the expression between brainstem and cortical microglia identified differentially expressed secreted proteins. The impact of some of these proteins on DIPGs was tested.

Results

DIPGs, pediatric HGGs of brainstem origin, survive and divide more in organotypic slice cultures originating in the brainstem as compared to the cortex. Moreover, brainstem microglia are better able to support tumors of brainstem origin. A comparison between the two microglial populations revealed differentially expressed genes. One such gene, interleukin-33 (IL33), is highly expressed in the pons of young mice and its DIPG receptor is upregulated in this context. Consistent with this observation, the expression levels of IL33 and its receptor, IL1RL1, are higher in DIPG biopsies compared to low-grade cortical gliomas. Furthermore, IL33 can enhance proliferation and clonability of HGGs of brainstem origin, while blocking IL33 in brainstem organotypic slice cultures reduced the proliferation of these tumor cells.

Conclusions

Crosstalk between DIPGs and the brainstem microenvironment, in particular microglia, through IL33 and other secreted factors, modulates spatiotemporal patterning of this HGG and could prove to be an important future therapeutic target.

The Nuclear Function of IL-33 in Desensitization to DNA Damaging Agent and Change of Glioma Nuclear Structure

Glioma, the most common subtype of primary brain tumor, is an aggressive and highly invasive neurologically tumor among human cancers. Interleukin-33 (IL-33) is considered as a dual functional cytokine, an alarmin upon tissue damage and a nuclear chromatin-associated protein. Despite that, IL-33 is known to foster the formation of the inflammatory tumor microenvironment and facilitate glioma progression, evidence showing nuclear IL-33 function is still poor. In this study using lentivirus-mediated IL-33 gene knockdown (IL33KD) and IL-33 overexpression (IL33oe) in rat C6 glioma cells and human glioma cell lines (U251MG and U87MG), we found that IL33oe-glioma cells had resistance to the insults of the alkylating agent, temozolomide (TMZ), possibly because of the increased expression of DNA repair genes (i.e., BRCA1, BRCA2, Rad51, FANCB, and FANCD) in IL33oe-glioma cells. Alternatively, examination of glioma nuclear shape from transmission electron microscopy (TEM) imaging analysis and immunofluorescence for histone protein H2A staining showed that IL33KD attenuated the abnormal cancerous nuclear characteristic, such as indentation, long clefts, and multiple nucleoids. Yet, IL33oe promoted the changes in glioma nuclear shapes, such as the formation of multiple lobes. We further found that histone proteins, H2A and H3, were reduced in IL33KD glioma cells. The non-histone DNA-binding nucleoproteins, the high mobility group A1 (HMGA1) and HMGA2, were also downregulated by IL33KD. In contrast, IL33oe increased H2A and H3 proteins and HMGA1 and HMGA2 in glioma cells. Altogether, the upregulation of nuclear IL-33 expression was along with an increase in the expression of DNA repair genes, contributing to the desensitization of glioma cells to DNA damaging agents. Moreover, nuclear IL-33 proteins in cooperation with chromatin-associated proteins regulate glioma nuclear structure, which might be crucial for glioma progression and malignancy.

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.

Therapeutic Opportunities of Interleukin-33 in the Central Nervous System

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is involved in various diseases. IL-33 exerts its effects via its heterodimeric receptor complex, which comprises suppression of tumorigenicity 2 (ST2) and the IL-1 receptor accessory protein (IL-1RAP). Increasing evidence has demonstrated that IL-33/ST2 signaling plays diverse but crucial roles in the homeostasis of the central nervous system (CNS) and the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infection, trauma, and ischemic stroke. In the current review, we focus on the functional roles and cellular signaling mechanisms of IL-33 in the CNS and evaluate the potential for diagnostic and therapeutic applications.

IL-33 as a Novel Serum Prognostic Marker of Intracerebral Hemorrhage

Objective

Interleukin 33 (IL-33) is a key cytokine involved in inflammation and oxidative stress. The significance of serum IL-33 levels on the prognosis of patients with intracerebral hemorrhage (ICH) has not been well studied. The purpose of this study is to determine whether there is a relationship between the serum IL-33 level and the prognosis of patients with ICH upon admission.

Methods

A total of 402 patients with confirmed ICH were included in this study. Their demographic data, medical history, laboratory data, imaging data, and clinical scores on admission were collected. At the same time, enzyme-linked immunoassay (ELISA) was used to detect the serum IL-33 levels of patients. The prognosis of patients was evaluated by mRS scale after 3 months, and mRS > 2 was defined as poor prognosis.

Results

Among 402 patients with ICH, the number of patients with good prognosis and poor prognosis after 3 months was 148 and 254, respectively. Compared with the ICH group with poor prognosis, the ICH group with good prognosis had lower baseline NHISS scores (p = 0.039) and hematoma volume (p = 0.025) and higher GCS scores (p < 0.001) and serum IL-33 levels (p < 0.001). The results of linear correlation analysis showed that serum IL-33 levels were significantly negatively correlated with baseline NHISS scores (r = −0.224, p = 0.033) and hematoma volume (r = −0.253, p = 0.046) but were significantly positively correlated with baseline GCS scores (r = 0.296, p = 0.020). The receiver operating characteristic curve (ROC) analysis showed that the sensitivity and specificity of serum IL-33 level in evaluating the prognosis of ICH were 72.1% and 74.3%, respectively. A cut-off value of serum IL-33 level < 109.3 pg/mL may indicate a poor prognosis for ICH.

Conclusions

Serum IL-33 level on admission may be a prognostic indicator of ICH, and its underlying mechanism needs further study.

Glioma-derived IL-33 orchestrates an inflammatory brain tumor microenvironment that accelerates glioma progression

Despite a deeper molecular understanding, human glioblastoma remains one of the most treatment refractory and fatal cancers. It is known that the presence of macrophages and microglia impact glioblastoma tumorigenesis and prevent durable response. Herein we identify the dual function cytokine IL-33 as an orchestrator of the glioblastoma microenvironment that contributes to tumorigenesis. We find that IL-33 expression in a large subset of human glioma specimens and murine models correlates with increased tumor-associated macrophages/monocytes/microglia. In addition, nuclear and secreted functions of IL-33 regulate chemokines that collectively recruit and activate circulating and resident innate immune cells creating a pro-tumorigenic environment. Conversely, loss of nuclear IL-33 cripples recruitment, dramatically suppresses glioma growth, and increases survival. Our data supports the paradigm that recruitment and activation of immune cells, when instructed appropriately, offer a therapeutic strategy that switches the focus from the cancer cell alone to one that includes the normal host environment.

High level of interleukin-33 in cancer cells and cancer-associated fibroblasts correlates with good prognosis and suppressed migration in cholangiocarcinoma

Interleukin 33 (IL-33) promotes cholangiocarcinoma (CCA) genesis in a mouse model, however, its function in human CCA has not been clearly understood. This study was aimed to investigate IL-33 level in CCA tissues and its clinicopathological correlations. The results revealed that IL-33 was found in both cancer cells and stromal cancer-associated fibroblast (CAFs) staining patterns which were divided into high (CH) and low level (CL) in cancer cells; and presence (FP) and absence (FA) in CAFs. Kaplan-Meier analysis showed that patients in the CL group were significantly correlated with a short 2-year survival time (P = 0.027). The CL/FP group had a shorter survival time compared to the other groups with statistical significance for 2-year (P = 0.030) and 5-year (P = 0.023) survivals. In contrast, CH/FP patients had significantly greater 2-year (P = 0.003) and 5-year (P = 0.003) survivals. Univariate and multivariate analysis confirmed that CL/FP was a significantly independent risk factor whereas CH/FP was a significant protective factor in CCA patients. High IL-33 expressing CCA cells had low migration, but they showed increased migration when IL-33 expression was knocked down. The low level of recombinant human IL-33 (rhIL-33) (0.002 - 2 ng/ml) could promote CCA cell migration, in contrast to the suppressive effect at a high dose (20 - 200 ng/ml). In conclusion, the combination of high IL-33 level in cancer cells and CAFs is a potentially good prognosis marker in CCA patients. The in vitro migration suppressive effect of IL-33 may be the potential mechanism supporting its role as a good prognostic marker in CCA patients. The obtained results strengthen IL-33 as a promising predictor and therapeutic target for CCA.

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.

The Interleukin-33/ST2 axis promotes glioma mesenchymal transition, stemness and TMZ resistance via JNK activation

IL-33 is an important member of the IL-1 family which has pleiotropic activities in innate and adaptive immune responses. Recently, some researchers have focused on the function of cellular immunity in the development of tumor. The biological role of IL-33 in glioma is poorly understood. In this study, we showed that glioma cells and tissues expressed higher levels of IL-33 and its receptor ST2 compared to normal brain. Clinically, IL-33 expression was associated with poor survival in patients with glioma. Administration of human IL-33 enhanced cell migration, invasion, epithelial to mesenchymal transition and stemness. Anti-ST2 blocked these effects of IL-33 on tumor. Mechanistically, IL-33 activated JNK signaling pathway via ST2 and increased the expression of key transcription factors that controlled the process of EMT and stemness. Moreover, IL-33 prevented temozolomide induced tumor apoptosis. Anti-ST2 or knockdown IL-33 increased the sensitivity of tumor to temozolomide. Thus, targeting the IL-33/ST2 axis may offer an opportunity to the treatment of glioma patients.

IL-33/ST2 axis promotes glioblastoma cell invasion by accumulating tenascin-C

Tenascin-C (TNC), a very large multimeric glycoprotein, is overexpressed in human glioblastomas, leading to a highly motile and invasive phenotype of glioma cells. However, the regulation of TNC expression in glioma has remained unclear until now. Our data suggest that interleukin-33 (IL-33) may promote the accumulation of TNC protein by autocrine or paracrine modes of action in glioma. In the present study, the expression levels of TNC, IL-33, and ST2 were measured in glioma tissue specimens, and the impact of altered IL-33 expression on TNC was investigated in vitro and in vivo. In contrast with control treatment, IL-33 treatment increased TNC expression, and knockdown of IL-33 attenuated TNC expression in glioma cells. Furthermore, IL-33 induced the activation of nuclear factor κB (NF-κB) and increased the expression of TNC in U251 cells. In addition, blockage of the IL-33-ST2-NFκB pathway resulted in downregulation of TNC production. IL-33 promoted glioma cell invasion by stimulating the secretion of TNC. Similarly, knockdown of TNC inhibited the invasiveness of glioma cells. These findings provide a novel perspective on the role of the IL-33/NF-κB/TNC signalling pathway in supporting cancer progression. Thus, targeting the IL-33/NF-κB/TNC signalling pathway may be a useful therapeutic approach in glioma.

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.

IL-17 induces the proliferation and migration of glioma cells through the activation of PI3K/Akt1/NF-κB-p65

Interleukin 17 (IL-17), as a pro-inflammatory cytokine, is up-regulated in the sera and tumor tissues of glioma patients; however the effects of IL-17 on glioma proliferation and migration remain unclear. In this study, the roles of IL-17 in the proliferation and migration of glioma cells and their potential mechanisms were determined. The results showed that IL-17 could not only enhance the proliferation and migration of cultured glioma cells (in vitro), but also promote the tumor formation of glioma cells in BALB/c nude mice (in vivo). Mechanical exploration revealed that IL-17 stimulation could increase the phosphorylation levels of Akt1 and NF-κB-p65 in glioma cells, and knockdown or inhibition of PI3K, Akt1 and NF-κB-p65 could also reduce the IL-17-induced proliferation and migration of the glioma cells. Moreover, PI3K/Akt1 was the upstream regulator of NF-κB-p65 activation in IL-17-incubated glioma cells. Furthermore, the inhibition of PI3K, Akt1 and NF-κB-p65 markedly suppressed the tumor formation of glioma cells induced by IL-17. Together, these data indicate that IL-17 can promote the proliferation and migration of glioma cells via PI3K/Akt1/NF-κB-p65 activation, and these findings might provide a new insight into glioma pathogenesis.

Expression and Function of IL-33/ST2 Axis in the Central Nervous System Under Normal and Diseased Conditions

Interleukin-33 (IL-33) is a well-recognized immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. The abundant expression of IL-33 in brain and spinal cord prompted many scientists to explore its unique role in the central nervous system (CNS) under physiological and pathological conditions. Indeed emerging evidence from over a decade's research suggests that IL-33 acts as one of the key molecular signaling cues coordinating the network between the immune and CNS systems, particularly during the development of neurological diseases. Here, we highlight the recent advances in our knowledge regarding the distribution and cellular localization of IL-33 and its receptor ST2 in specific CNS regions, and more importantly the key roles IL-33/ST2 signaling pathway play in CNS function under normal and diseased conditions.

The Pleiotropic Immunomodulatory Functions of IL-33 and Its Implications in Tumor Immunity

Interleukin-33 (IL-33) is a IL-1 family member of cytokines exerting pleiotropic activities. In the steady-state, IL-33 is expressed in the nucleus of epithelial, endothelial, and fibroblast-like cells acting as a nuclear protein. In response to tissue damage, infections or necrosis IL-33 is released in the extracellular space, where it functions as an alarmin for the immune system. Its specific receptor ST2 is expressed by a variety of immune cell types, resulting in the stimulation of a wide range of immune reactions. Recent evidences suggest that different IL-33 isoforms exist, in virtue of proteolytic cleavage or alternative mRNA splicing, with potentially different biological activity and functions. Although initially studied in the context of allergy, infection, and inflammation, over the past decade IL-33 has gained much attention in cancer immunology. Increasing evidences indicate that IL-33 may have opposing functions, promoting, or dampening tumor immunity, depending on the tumor type, site of expression, and local concentration. In this review we will cover the biological functions of IL-33 on various immune cell subsets (e.g., T cells, NK, Treg cells, ILC2, eosinophils, neutrophils, basophils, mast cells, DCs, and macrophages) that affect anti-tumor immune responses in experimental and clinical cancers. We will also discuss the possible implications of diverse IL-33 mutations and isoforms in the anti-tumor activity of the cytokine and as possible clinical biomarkers.

The Pro-tumorigenic IL-33 Involved in Antitumor Immunity: A Yin and Yang Cytokine

Interleukin-33 (IL-33), considered as an alarmin released upon tissue stress or damage, is a member of the IL-1 family and binds the ST2 receptor. First described as a potent initiator of type 2 immune responses through the activation of T helper 2 (T_H2) cells and mast cells, IL-33 is now also known as an effective stimulator of T_H1 immune cells, natural killer (NK) cells, iNKT cells, and CD8 T lymphocytes. Moreover, IL-33 was shown to play an important role in several cancers due to its pro and anti-tumorigenic functions. Currently, IL-33 is a possible inducer and prognostic marker of cancer development with a direct effect on tumor cells promoting tumorigenesis, proliferation, survival, and metastasis. IL-33 also promotes tumor growth and metastasis by remodeling the tumor microenvironment (TME) and inducing angiogenesis. IL-33 favors tumor progression through the immune system by inducing M2 macrophage polarization and tumor infiltration, and upon activation of immunosuppressive cells such as myeloid-derived suppressor cells (MDSC) or regulatory T cells. The anti-tumor functions of IL-33 also depend on infiltrated immune cells displaying T_H1 responses. This review therefore summarizes the dual role of this cytokine in cancer and suggests that new proposals for IL-33-based cancer immunotherapies should be considered with caution.

Genetic variants in IL-33/ST2 pathway with the susceptibility to hepatocellular carcinoma in a Chinese population

Interleukin (IL)-33/ST2 pathway plays a pivotal role in tumorigenesis through influencing cancer stemness, tumor growth, metastasis, angiogenesis, and accumulation of regulatory T cells in tumor microenvironments. The aim of this study was to investigate the association of IL-33 rs7025417 and ST2 rs3821204 with the risk of hepatocellular carcinoma (HCC). Genotyping of IL-33 rs7025417 and ST2 rs3821204 was carried out using a Taqman assay. IL-33 and ST2 mRNA was examined using real-time PCR and plasma IL-33 and sST2 levels were measured using enzyme-linked immunosorbent assay. The ST2 rs3821204 CC genotype was associated with a significantly increased risk of HCC (CC vs. GG: adjusted OR = 2.29, 95% CI, 1.39-3.78; dominant model: adjusted OR = 1.58, 95% CI, 1.12-2.23; recessive model: adjusted OR = 1.88, 95% CI, 1.21-2.93; C vs. G: adjusted OR = 1.53, 95% CI, 1.20-1.95). Gene-environment interaction analysis showed that the risk effect of rs3821204 CG/CC genotypes was more evident in smokers (adjusted OR = 1.70, 95% CI, 1.13-2.55) and drinkers (adjusted OR = 1.57, 95% CI, 1.04-2.37). The increased risk was also observed in combined analysis. Moreover, HCC patients with ST2 rs3821204 CC genotype had higher levels of mRNA and protein expression (P < 0.05). These findings suggest that ST2 rs3821204 CC genotype may contribute to hepatocarcinogenesis by enhancing ST2 production at the transcriptional and translational level.

IL-33/ST2 Pathway as a Rational Therapeutic Target for CNS Diseases

Interleukin (IL)-33 is a member of the interleukin-1 cytokine family that is produced by many different types of tissues including the central nervous system (CNS). IL-33 mediates its effects via its heterodimeric receptor complex, comprised of ST2 and the IL-1 receptor accessory protein (IL-1RAcp). As a pleiotropic nuclear cytokine, IL-33 is a crucial factor in the development of cardiovascular diseases, allergic diseases, infectious diseases, and autoimmune diseases. Recently, accumulated evidence shows that the IL-33/ST2 axis plays a crucial and diverse role in the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infectious diseases, traumatic CNS injury, chronic pain, etc. In this review, we discuss the recent findings in the cellular signaling of IL-33 and advancement of the role of IL-33 in several CNS diseases, as well as its therapeutic potential for the treatment of those diseases.

IL‑33 enhances glioma cell migration and invasion by upregulation of MMP2 and MMP9 via the ST2-NF-κB pathway

As an important member of the interleukin (IL)-1 family, IL‑33 plays a significant role in tumor progression. To explore this, we previously analyzed the association between IL‑33 expression and the prognosis of patients with glioma. However, the function of the IL‑33/ST2 axis in glioma remained unclear. In the present study, immunofluorescent staining results revealed that the expression levels of IL‑33 and ST2 receptor in glioma tissues were higher than those in normal brain tissues. Invasion and migration assays demonstrated that IL‑33 significantly increased glioma cell invasion and migration in vitro. Furthermore, knockdown of ST2 by siRNA attenuated the IL‑33-induced increase in invasion and migration. In addition, ELISA results revealed that IL‑33 upregulated the expression of matrix metalloproteinase (MMP)2 and MMP9. Western blot analysis results indicated that IL‑33 stimulation increased the phosphorylation of nuclear factor-κB (NF-κB) in a time- and dose-dependent manner. Moreover, silencing of the NF-κB pathway by BAY 11‑7082 resulted in the inhibition of IL‑33-induced invasion and migration, as well as the downregulation of MMP2 and MMP9 production. These findings indicate that IL‑33 may be involved in the process of glioma cell invasion and migration by upregulating MMP2 and MMP9 via the ST2-NF-κB signaling pathway. Thus, IL‑33 may be a novel therapeutic target for glioma.