Dual role of IL-37 in the progression of tumors

The role of IL-37 in gastrointestinal diseases

Gastrointestinal mucosal surface is frequently under challenge due to it's the large surface area and most common entry of microbes. IL-37, an anti-inflammatory cytokine, regulates local and systemic host immunity. H. pylori infection leads to the inhibition of IL-37 in the gastric mucosa, contributing to heightened mucosal inflammation and destruction, thereby facilitating increased proliferation of H. pylori. Food allergy, due to immune dysregulation, also contribute to GI injury. On the other hand, elevated levels of IL-37 observed in gastric cancer patients align with reduced host immunity at the cellular and humoral levels, indicating that IL-37 may contribute to the development of gastric cancer via suppressing pro-inflammatory responses. While IL-37 provides protection in an IBD animal model, the detection of highly produced IL-37 in IBD patients suggests a stage-dependent role, being protective in acute inflammation but potentially exacerbates the development of IBD in chronic conditions. Moreover, elevated colonic IL-37 in CRC correlates with overall survival time and disease time, indicating a protective role for IL-37 in CRC. The differential regulation and expression of IL-37 between upper- and lower-GI organs may be attributed to variations in the microbial flora. This information suggests that IL-37 could be a potential therapeutic agent, depending on the stage and location.

Agree to disagree: The contradiction between IL-18 and IL-37 reveals shared targets in cancer

IL-37 is a newly discovered member of the IL-1 cytokine family which plays an important role in regulating inflammation and maintaining physiological homeostasis. IL-37 showed a close relationship with IL-18, another key cytokine in inflammation regulation and cancer development. IL-37 affects the function of IL-18 either by binding to IL-18Rα, a key subunit of both IL-37 and IL-18 receptor, or by drastically neutralizing the IL-18 protein expression of IL-18 binding protein, an important natural inhibitory molecule of IL-18. Moreover, as another subunit receptor of IL-37, IL-1R8 can suppress IL-18Rα expression, functioning as a surveillance mechanism to prevent overactivation of both IL-18 and IL-37 signaling pathways. While IL-18 and IL-37 share the same receptor subunit, IL-18 would in turn interfere with IL-37 signal transduction by binding to IL-18Rα. It is also reported that IL-18 and IL-37 demonstrated opposing effects in a variety of cancers, such as glioblastoma, lung cancer, leukemia, and hepatocellular cancer. Although the mutual regulation of IL-18 and IL-37 and their diametrically opposed effects in cancers has been reported, IL-18 has not been taken into consideration when interpreting clinical findings and conducting mechanism investigations related to IL-37 in cancer. We aim to review the recent progress in IL-18 and IL-37 research in cancer and summarize the correlation between IL-18 and IL-37 in cancer based on their expression level and underlying mechanisms, which would provide new insights into elucidating the conflicting roles of IL-18 and IL-37 in cancer and bring new ideas for translational research related to IL-18 and IL-37.

The anti-inflammatory cytokine IL-37 improves the NK cell-mediated anti-tumor response

IL-37 is a member of the IL-1 superfamily exerting anti-inflammatory functions in a number of diseases. Extracellular IL-37 triggers the inhibitory receptor IL-1R8 that is known to regulate different NK cell pathways and functional activities including their anti-tumor effect. However, the effect of IL-37 on human NK cell functions is still to be unveiled. This study aimed to investigate the functional effect of IL-37 in human NK cells activated with IL-15. We found that IL-37 enhanced both NK cell cytotoxic activity against different tumor cell lines and cytokines production. These effects were associated with increased phosphorylation of ERK and NF-Kb. The improved NK cell activity was also strictly related to a time-dependent GSK3β-mediated degradation of IL-1R8. The enhanced activation profile of IL-37 treated NK cells possibly due to IL-1R8 degradation was confirmed by the results with IL-1R8-silenced NK cells. Lastly, in line with these data, through the analysis of the TNM plot database of a large group of patients, IL-37 mRNA expression was found to be significantly lower in colon and skin cancers than in normal tissues. Colon adenocarcinoma and neuroblastoma patients with higher IL-37 mRNA levels had significantly higher overall survival, suggesting that the presence of IL-37 might be considered an independent positive prognostic factor for this tumor. Our results provide novel information on the mechanisms regulating IL-1R8 function in human NK cells, highlighting the IL-37-IL-1R8 axis as a potential new target to improve the anti-tumor immune response.

Interleukin-37 gene expression is down-regulated in patients with acute myeloid leukemia and shown to be affected by CD14 and HLA-DR immunophenotypes

Recent evidence has indicated that interleukin 37 (IL-37) shows down-regulated expression in patients with acute myeloid leukemia (AML), but its association with immunophenotypic markers has not been explored. In the current study, IL37 mRNA expression was analyzed in the peripheral blood of 131 AML patients and 100 controls using the 2-ΔΔCt method (fold change), which was based on the principles of quantitative real-time polymerase chain reaction. AML patients were characterized in terms of gender, therapy, fms-like tyrosine kinase 3/internal tandem duplication (FLT3/ITD) and nucleophosmin 1 (NPM1) mutations, French-American-British classification (FAB), World Health Organization (WHO) classification, and immunophenotypes of 25 cytoplasmic and surface markers. IL37 mRNA expression was given as median and interquartile range. Low expression of IL37 mRNA (0.273 [0.062-0.456]) was found in AML patients. This reduced expression was more pronounced in females than in males but the difference was significant before the Bonferroni correction (0.196 [0.045-0.411] vs. 0.4 [0.153-0.466]; probability [p] = 0.008; corrected p = 0.064). In addition, the FAB M4 type (0.109 [0.031-0.269]) and the WHO PML-RARA type (0.171 [0.061-0.482]) had the lowest expression of IL37 mRNA among the other types. For immunophenotypes, only two significant differences were found. First, CD14-positive patients showed a lower level of expression than CD14-negative patients (0.146 [0.033-0.413] vs. 0.323 [0.108-0.468]; p = 0.02). Second, HLA-DR-positive patients showed a higher level of expression than HLA-DR-negative patients (0.325 [0.163-0.474] vs. 0.214 [0.045-0.42]; p = 0.04). However, the corrected p-value was not significant in both cases (p > 0.05). In conclusion, IL37 mRNA expression was down-regulated in AML patients, especially females, and those with the FAB M4 type and the WHO PML-RARA type. This expression may be affected by the immunophenotypic markers CD14 and HLA-DR.

Novel insights into IL-37: an anti-inflammatory cytokine with emerging roles in anti-cancer process

Interleukin-37 (IL-37) is a newly discovered member of IL-1 family. The cytokine was proved to have extensive protective effects in infectious diseases, allergic diseases, metabolic diseases, autoimmune diseases and tumors since its discovery. IL-37 was mainly produced by immune and some non-immune cells in response to inflammatory stimulus. The IL-37 precursors can convert into the mature forms after caspase-1 cleavage and activation intracellularly, and then bind to Smad-3 and transfer to the nucleus to inhibit the production and functions of proinflammatory cytokines; extracellularly, IL-37 binds to cell surface receptors to form IL-37/IL-18Rα/IL-1R8 complex to exert immunosuppressive function via inhibiting/activating multiple signal pathways. In addition, IL-37 can attenuate the pro-inflammatory effect of IL-18 through directly or forming an IL-37/IL-18BP/IL-18Rβ complex. Therefore, IL-37 has the ability to suppress innate and acquired immunity of the host, and effectively control inflammatory stimulation, which was considered as a new hallmark of cancer. Specifically, it is concluded that IL-37 can inhibit the growth and migration of tumor cells, prohibit angiogenesis and mediate the immunoregulation in tumor microenvironment, so as to exert effective anti-tumor effects. Importantly, latest studies also showed that IL-37 may be a novel therapeutic target for cancer monitoring. In this review, we summarize the immunoregulation roles and mechanisms of IL-37 in anti-tumor process, and discuss its progress so far and potential as tumor immunotherapy.

The intellectual base and research fronts of IL-37: A bibliometric review of the literature from WoSCC

Background

IL-37 is a recently identified cytokine with potent immunosuppressive functions. The research fronts of IL-37 are worth investigating, and there is no bibliometric analysis in this field. The purpose of this study is to construct the intellectual base and predict research hotspots of IL-37 research both quantitatively and qualitatively according to bibliometric analysis.

Methods

The articles were downloaded from the Web of Science Core Collection (WoSCC) database from the inception of the database to 1 April 2022. CiteSpace 5.8.R3 (64-bit, Drexel University, Philadelphia, PA, USA) and Online Analysis Platform of Literature Metrology (https://bibliometric.com/) were used to perform bibliometric and knowledge-map analyses.

Results

A total of 534 papers were included in 200 academic journals by 2,783 authors in 279 institutions from 50 countries/regions. The journal Cytokine published the most papers on IL-37, while Nature Immunology was the most co-cited journal. The publications belonged mainly to two categories of Immunology and Cell Biology. USA and China were the most productive countries. Meanwhile, the University of Colorado Denver in USA produced the highest number of publications followed by Radboud University Nijmegen in the Netherlands and Monash University in Australia. Charles A. Dinarello published the most papers, while Marcel F. Nold had the most co-citations. Top 10 co-citations on reviews, mechanisms, and diseases were regarded as the knowledge base. The keyword co-occurrence and co-citations of references revealed that the mechanisms and immune-related disorders were the main aspects of IL-37 research. Notably, the involvement of IL-37 in various disorders and the additional immunomodulatory mechanisms were two emerging hotspots in IL-37 research.

Conclusions

The research on IL-37 was thoroughly reviewed using bibliometrics and knowledge-map analyses. The present study is a benefit for academics to master the dynamic evolution of IL-37 and point out the direction for future research.