Integrative genomic analyses of a novel cytokine, interleukin-34 and its potential role in cancer prediction

Colony stimulating factor-1 (CSF-1) signalling is predictive of response to immune checkpoint inhibitors in advanced non-small cell lung cancer

The identification of biomarkers related to treatment in patients with non-small cell lung cancer (NSCLC) treated with immune checkpoint inhibitors (ICIs) represents a significant challenge. The aim of this study was to determine the predictive value of macrophage-related markers assessed in plasma and tissue samples of patients with NSCLC undergoing ICI treatment. This bicentric study included a prospective cohort of 88 patients with advanced NSCLC who received first-line therapy with ICI (either as monotherapy or in combination with chemotherapy) or chemotherapy alone (CT). Samples were collected from the patients at baseline and during follow-up. Plasma levels of CSF-1 and IL-34 were measured using ELISA, while expression levels of the macrophage receptors CD163 and CSF-1-R were evaluated using immunohistochemistry on lung biopsies. At baseline, the median plasma CSF-1 expression was higher in patients who did not respond to immunotherapy compared to those who responded (8898 pg/mL vs. 14031 pg/mL, p = 0.0005). Importantly, high CSF-1 levels at the initial assessment were associated with disease progression regardless of the treatment received. Furthermore, high CSF-1 levels were associated with shorter progression-free survival (PFS) and overall survival (OS) in patients receiving ICI therapy, but not in those treated with chemotherapy. There was no correlation between IL-34, CSF-1R, CD163 and therapeutic response. We observed in vitro that the activation of lymphocytes mediated by pembrolizumab was hindered by the treatment of PBMC with recombinant CSF-1, suggesting that CSF-1 creates a systemic immunosuppressive state that interferes with ICI treatment. In conclusion, baseline CSF-1 levels represent a potential predictive marker to ICI treatment in NSCLC.

Sp1 Controls the Basal Level of Interleukin-34 Transcription

Interleukin-34 (IL-34) is a cytokine that plays important roles at steady state and in diseases. The induced or inhibited expression of IL-34 by stimuli has been deeply investigated. However, the regulation of IL-34 basal expression is largely unknown. The aim of this study is to investigate whether IL-34 expression is regulated by a general transcription factor Specificity Protein 1 (Sp1) at transcription level. By using bioinformatic software, four putative Sp1-binding sites overlapping GC boxes were found in the core promoter region of IL-34. Alignment of the core promoter sequences of mammalian IL-34 showed GC box-C (-62/-57) and D (-11/-6) were conserved in some mammals. Luciferase assay results showed that only deletion of GC box-C (-62/-57) significantly reduced luciferase activities of IL-34 core promoter in SH-SY5Y cells. By using electrophoretic mobility shift assay (EMSA), it was found that Sp1 specifically interacted with GC box-C sequence CCCGCC (-62/-57) in the core promoter of IL-34. By using chromatin immunoprecipitation (ChIP), it was discovered that Sp1 bound to the core promoter of IL-34 in living cells. In addition, silencing of Sp1 expression by its specific siRNA reduced IL-34 mRNA and protein levels significantly in SH-SY5Y cells. Likewise, IL-34 expression was inhibited in a dose-dependent manner by a Sp1 inhibitor Plicamycin. Furthermore, silencing of Sp1 also downregulated mRNA and protein expression of IL-34 in GES-1 and 293T cell lines, suggesting that IL-34 transcription regulated by Sp1 was not cell-type specific. Taken together, these results indicate that Sp1 controls the basal level of IL-34 transcription.

Interleukin-34 and immune checkpoint inhibitors: Unified weapons against cancer

Interleukin-34 (IL-34) is a cytokine that is involved in the regulation of immune cells, including macrophages, in the tumor microenvironment (TME). Macrophages are a type of immune cell that can be found in large numbers within the TME and have been shown to have a role in the suppression of immune responses in cancer. This mmune suppression can contribute to cancer development and tumors' ability to evade the immune system. Immune checkpoint inhibitors (ICIs) are a type of cancer treatment that target proteins on immune cells that act as "checkpoints," regulating the activity of the immune system. Examples of these proteins include programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). ICIs work by blocking the activity of these proteins, allowing the immune system to mount a stronger response against cancer cells. The combination of IL-34 inhibition with ICIs has been proposed as a potential treatment option for cancer due to the role of IL-34 in the TME and its potential involvement in resistance to ICIs. Inhibiting the activity of IL-34 or targeting its signaling pathways may help to overcome resistance to ICIs and improve the effectiveness of these therapies. This review summarizes the current state of knowledge concerning the involvement of IL-34-mediated regulation of TME and the promotion of ICI resistance. Besides, this work may shed light on whether targeting IL-34 might be exploited as a potential treatment option for cancer patients in the future. However, further research is needed to fully understand the mechanisms underlying the role of IL-34 in TME and to determine the safety and efficacy of this approach in cancer patients.

Prognostic value of interleukin-34 and interleukin-38 in patients with newly diagnosed atrial fibrillation

Background

Interleukin (IL)-34 and IL-38 are associated with cardiovascular disease (CVD). However, their involvement in atrial fibrillation (AF) and AF-associated adverse events remains uncertain. Therefore, we aimed to investigate their association with various AF prognostic factors in a cohort study and assessed their predictive value for the prognosis of patients with AF.

Methods

Patients with new-onset non-valvular AF were consecutively enrolled between 2013 and 2015 at the Department of Cardiovascular Medicine of the Southwest Hospital of the Army Medical University (Third Military Medical University) in Chongqing, China. The endpoints included stroke and all-cause mortality. The baseline levels of plasma IL-34, IL-38, NT-proBNP, high-sensitivity cardiac troponin T (hs-cTnT), and GDF-15 were measured and their correlation with AF-related adverse events were analyzed in a Cox proportional-hazards regression model. The C-statistic, net reclassification improvement (NRI), and integrated discrimination improvement (IDI) were used to evaluate the performance of the AF prognostic models. Decision curve analysis (DCA) was used to evaluate the clinical net benefit of the original and modified models.

Results

A total of 299 patients with new-onset AF were enrolled. During the median follow-up time of 28 (IQR: 27, 29) months, the higher levels of IL-34 were associated with a lower risk of stroke, and the higher levels of IL-38 were associated with an increased risk of all-cause death (all adjusted P < 0.05). In addition, elevated hs-cTnT and NT-proBNP concentrations were associated with a higher risk of stroke and all-cause mortality (all adjusted P < 0.05). Furthermore, the CHA₂DS₂-VASc score combined with IL-38 and NT-proBNP significantly improved the C-statistic, IDI, and NRI (all P < 0.01). There was no statistically significant difference (all P > 0.05) in the discrimination power between the preference models and the ABC (age, biomarkers, and clinical history) score for the two prognostic outcomes.

Conclusion

Our results suggested that IL-34 and IL-38 were independently associated with stroke and all-cause mortality in patients with AF. Moreover, adding IL-38 and NT-proBNP to the CHA₂DS₂-VASc score significantly improved its predictive ability of AF-related all-cause death. Finally, the preference model performed equally well as the ABC score in predicting AF prognosis.

Interleukin 34 in Disease Progressions: A Comprehensive Review

IL-34, a cytokine, discovered a decade before and is known to be a colony stimulating factor CSF-1 receptor (CSF-1R) ligand. Along with CSF-1R, it also interacts with syndecan-1 receptors and protein-tyrosine phosphatase (PTP-ζ). Hence, IL-34 takes part in a number of biological activities owing to its involvement in different signaling pathways. This review was done to analyze the recent studies on the functions of IL-34 in progression of diseases. The role of IL-34 under the physiological and pathological settings is studied by reviewing current data. In the last ten years, studies suggested that the IL-34 was involved in the regulation of morbid states such as inflammatory diseases, infections, transplant rejection, autoimmune diseases, neurologic diseases, and cancer. In general, the involvement of IL-34 is observed in many serious health ailments like metabolic diseases, heart diseases, infections and even cancer. As such, IL-34 can be regarded as a therapeutic target, potential biomarker or as a therapeutic tool, which ought to be assessed in future research activities.

Interleukin-34 deficiency aggravates development of colitis and colitis-associated cancer in mice

BACKGROUND

Although expression of interleukin (IL)-34 is upregulated in active ulcerative colitis (UC), the molecular function and underlying mechanism are largely unclear.

AIM

To investigate the function of IL-34 in acute colitis, in a wound healing model and in colitis-associated cancer in IL-34-deficient mice.

METHODS

Colitis was induced by administration of dextran sodium sulfate (DSS), and carcinogenesis was induced by azoxymethane (AOM). Whether the impact of IL-34 on colitis was dependent on macrophages was validated by depletion of macrophages in a murine model. The association between IL-34 expression and epithelial proliferation was studied in patients with active UC.

RESULTS

IL-34 deficiency aggravated murine colitis in acute colitis and in wound healing phase. The effect of IL-34 on experimental colitis was not dependent on macrophage differentiation and polarization. IL-34-deficient mice developed more tumors than wild-type mice following administration of AOM and DSS. No significant difference was shown in degree of cellular differentiation in tumors between wild-type and IL-34-deficient mice. IL-34 was dramatically increased in the active UC patients as previously reported. More importantly, expression of IL-34 was positively correlated with epithelial cell proliferation in patients with UC.

CONCLUSION

IL-34 deficiency exacerbates colonic inflammation and accelerates colitis-associated carcinogenesis in mice. It might be served as a potential therapeutic target in UC.

Self-Renewal of Macrophages: Tumor-Released Factors and Signaling Pathways

Macrophages are the most abundant immune cells of the tumor microenvironment (TME) and have multiple important functions in cancer. During tumor growth, both tissue-resident macrophages and newly recruited monocyte-derived macrophages can give rise to tumor-associated macrophages (TAMs), which have been associated with poor prognosis in most cancers. Compelling evidence indicate that the high degree of plasticity of macrophages and their ability to self-renew majorly impact tumor progression and resistance to therapy. In addition, the microenvironmental factors largely affect the metabolism of macrophages and may have a major influence on TAMs proliferation and subsets functions. Thus, understanding the signaling pathways regulating TAMs self-renewal capacity may help to identify promising targets for the development of novel anticancer agents. In this review, we focus on the environmental factors that promote the capacity of macrophages to self-renew and the molecular mechanisms that govern TAMs proliferation. We also highlight the impact of tumor-derived factors on macrophages metabolism and how distinct metabolic pathways affect macrophage self-renewal.

Targeting IL-34/MCSF-1R Axis in Colon Cancer

Colorectal carcinoma (CRC) is one of the most common neoplasias in the Western world and it is still one of the most deadly cancers worldwide mainly due to the fact that metastatic CRC is not responsive to current pharmacologic treatment. Identification of pathways that sustain CRC cell behaviour could help develop effective therapeutic compounds. A large body of evidence indicates that colon carcinogenesis is a dynamic process in which multiple cell types present in the tumor microenvironment either stimulate or suppress CRC cell growth, survival, and diffusion mainly via the production of cytokines. Interleukin-34 (IL-34), a cytokine initially known for its ability to regulate monocyte/macrophage survival and function, is highly produced in human CRC by both cancer cells and non-tumoral cells. IL-34 function is mainly mediated by interaction with the macrophage colony-stimulating factor-1 receptor (MCSF-1R), which is also over-expressed by CRC cells as well as by tumour-associated macrophages (TAMs) and cancer-associated fibroblasts. IL-34-driven MCSF-1R activation triggers several pro-tumoral functions in the colon. In this article, we review the current understanding of the involvement of IL-34 and its receptor in CRC, with particular attention to the available evidence about the IL-34/MCSF-1R axis-mediated regulation of TAMs and the role of IL-34 and MCSF-1R in promoting cancer resistance to chemotherapy and immunotherapy

Interleukin-34 promotes tumorigenic signals for colon cancer cells

Colorectal carcinoma (CRC) is one of the most common forms of malignancy in the Western world. Accumulating evidence indicates that colon carcinogenesis is tightly controlled by tumour-associated immune cells and stromal cells, which can either stimulate or suppress CRC cell growth and survival, mainly via the production of cytokines. Interleukin-34 (IL-34), a cytokine known to regulate mainly monocyte/macrophage survival and function, is highly produced within the CRC microenvironment by several cell types, including cancer cells, tumour-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), and regulates the pro-tumoural functions of such cells. In this article, we summarize the available data supporting the multiple effects of IL-34 in human CRC.

IL-34 affects fibroblast-like synoviocyte proliferation, apoptosis and function by regulating IL-17

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by proliferation and insufficient apoptosis of fibroblast-like synoviocytes (FLSs).The biology and functions of interleukin (IL)-34 are only beginning to be uncovered. We previously demonstrated IL-34 could upregulate the expression of IL-17 in RA patients. In this study, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry of Annexin V and PI staining were performed to assess cell proliferation and apoptosis progression in RA-FLSs after stimulated with increasing concentrations of IL-34, respectively. Inflammatory cytokines and angiogenic factors were measured using quantitative real-time PCR, Western blotting and ELISA. We explored the association between IL-34 and RA-FLS proliferation and apoptosis in the context of RA. Stimulating RA-FLSs with different concentrations of IL-34 significantly promoted the proliferation and inhibited the apoptosis of RA-FLSs in a concentration-dependent manner. Neutralization of IL-17 with the IL-17 inhibitor plumbagin (PB) reduced the effects of IL-34. Proinflammatory cytokine (IL-17A IL-6 and tumor necrosis factor-α, TNF-α) and angiogenic factor (vascular endothelial growth factor, VEGF and hypoxia-inducible factor-1α, HIF-1α) expression was markedly upregulated in RA-FLSs stimulated by IL-34. PB-mediated inhibition of IL-17A also decreased the expression of IL-6, TNF-α, HIF-1α and VEGF in RA-FLSs. Taken together, these findings suggest that targeting IL-34 production in RA-FLSs may be a therapeutic strategy for RA.

Involvement of the M-CSF/IL-34/CSF-1R pathway in malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer related to asbestos exposure. The tumor microenvironment content, particularly the presence of macrophages, was described as crucial for the development of the disease. This work aimed at studying the involvement of the M-CSF (CSF-1)/IL-34/CSF-1R pathway in the formation of macrophages in MPM, using samples from patients.

Methods

Pleural effusions (PEs), frozen tumors, primary MPM cells and MPM cell lines used in this study belong to biocollections associated with clinical databases. Cytokine expressions were studied using real-time PCR and ELISA. The Cancer Genome Atlas database was used to confirm our results on an independent cohort. An original three-dimensional (3D) coculture model including MPM cells, monocytes from healthy donors and a tumor antigen-specific cytotoxic CD8 T cell clone was used.

Results

We observed that high interleukin (IL)-34 levels in PE were significantly associated with a shorter survival of patients. In tumors, expression of CSF1 was correlated with ‘M2-like macrophages’ markers, whereas this was not the case with IL34 expression, suggesting two distinct modes of action of these cytokines. Expression of IL34 was higher in MPM cells compared with primary mesothelial cells. Particularly, high expression of IL34 was observed in MPM cells with an alteration of CDKN2A. Finally, using 3D coculture model, we demonstrated the direct involvement of MPM cells in the formation of immunosuppressive macrophages, through activation of the colony stimulating factor-1 receptor (CSF1-R) pathway, causing the inhibition of cytotoxicity of tumor antigen-specific CD8⁺ T cells.

Conclusions

The M-CSF/IL-34/CSF-1R pathway seems strongly implicated in MPM and could constitute a therapeutic target to act on immunosuppression and to support immunotherapeutic strategies.

IL-34 and CSF-1, deciphering similarities and differences at steady state and in diseases

Although IL-34 and CSF-1 share actions as key mediators of monocytes/macrophages survival and differentiation, they also display differences that should be identified to better define their respective roles in health and diseases. IL-34 displays low sequence homology with CSF-1 but has a similar general structure and they both bind to a common receptor CSF-1R, although binding and subsequent intracellular signaling shows differences. CSF-1R expression has been until now mainly described at a steady state in monocytes/macrophages and myeloid dendritic cells, as well as in some cancers. IL-34 has also 2 other receptors, protein-tyrosine phosphatase zeta (PTPζ) and CD138 (Syndecan-1), expressed in some epithelium, cells of the central nervous system (CNS), as well as in numerous cancers. While most, if not all, of CSF-1 actions are mediated through monocyte/macrophages, IL-34 has also other potential actions through PTPζ and CD138. Additionally, IL-34 and CSF-1 are produced by different cells in different tissues. This review describes and discusses similarities and differences between IL-34 and CSF-1 at steady state and in pathological situations and identifies possible ways to target IL-34, CSF-1, and its receptors.

Emerging roles of IL-34 in health and disease

Macrophages are part of the innate immune system and are present in every organ of the body. They fulfill critical roles in tissue homeostasis and development and are involved in various pathologies. An essential factor for the development, homeostasis, and function of mononuclear phagocytes is the colony stimulating factor-1 receptor (CSF-1R), which has two known ligands: CSF-1 and interleukin-34 (IL-34). While CSF-1 has been extensively studied, the biology and functions of IL-34 are only now beginning to be uncovered. In this review, we discuss recent advances of IL-34 biology in health and disease with a specific focus on mononuclear phagocytes.

Interleukin-34 expression in ovarian cancer: a possible correlation with disease progression

Ovarian cancer is the second-most lethal gynecological malignancy and the seventh-commonest cause of cancer-related death in women around the world. Most of the ovarian cancer patients are diagnosed at advanced stages and suffer from recurrence after primary cytoreductive surgery and standard first-line chemotherapy. Thus, the successful management of ovarian cancer patients requires the identification of factors that contribute to progression and relapse. Interleukin-34 (IL-34) is a novel cytokine that acts as a tissue-specific ligand of colony-stimulating factor-1 receptor (CSF-1R). In cancer, IL-34 exerts pro-tumorigenic functions that promote tumor growth, metastasis, angiogenesis, immune suppression and therapeutic resistance. In this study, we evaluate the impact of IL-34 on progression and survival of ovarian cancer patients. First, IL-34 was found to be expressed in several human ovarian cancer cell lines and cancer tissues from patients. The expression of IL-34 was enhanced by cytotoxic chemotherapy in ovarian cancer cell lines and cancer tissues from chemotherapy-treated ovarian cancer patients. Importantly, high IL-34 expression correlated with worse progression-free survival (PFS) and overall survival in different cohorts. The assessment of PFS based on a combination between IL34 expression and other related genes such as CSF1R and CD163 helped further to reach more statistical significance compared with IL34 alone. Furthermore, in the murine ovarian cancer cell HM-1 in vivo model, it was suggested that IL-34-derived tumor cells was correlated with tumor progression and survival by modulating the immune environment. Collectively, these findings indicate a possible correlation between IL-34 expression and disease progression in ovarian cancer patients and the mouse model.

Role of Interleukin-34 in Cancer

Cross-talk between cancer cells and the immune cells occurring in the tumor microenvironment is crucial in promoting signals that foster tumor growth and metastasis. Both cancer cells and immune cells secrete various interleukins (IL), which, either directly or indirectly, stimulate cancer-cell proliferation, survival, and diffusion, as well as contribute to sculpt the immune microenvironment, thereby amplifying tumorigenic stimuli. IL-34, a cytokine produced by a wide range of cells, has been initially involved in the control of differentiation, proliferation, and survival of myeloid cells. More recent studies documented the overexpression of IL-34 in several cancers, such as hepatocarcinoma, osteosarcoma, multiple myeloma, colon cancer, and lung cancer, and showed that tumor cells can produce and functionally respond to this cytokine. In this review, we summarize the multiple roles of IL-34 in various cancers, with the aim to better understand the relationship between the expression of this cytokine and cancer behavior and to provide new insights for exploring a new potential therapeutic target.

Interleukin-34 mediated by hepatitis B virus X protein via CCAAT/enhancer-binding protein α contributes to the proliferation and migration of hepatoma cells

Objectives

Interleukin‐34 (IL‐34) is associated with hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). However, the role and associated mechanisms of IL‐34 in HBV‐related HCC remain unclear. In this study, the expression, biological function and associated mechanisms of IL‐34 in HBV‐related HCC cells were investigated.

Methods

IL‐34 expression induced by HBV and HBV X (HBX) gene was measured in hepatoma cells. The role of CCAAT/enhancer‐binding protein α (CEBP/α) in HBX‐induced IL‐34 expression was examined. The signal pathways involved in the expression of CEBP/α and IL‐34 induced by HBX were assessed. The role of IL‐34 in the proliferation and migration of HCC cells, and related mechanisms were explored.

Results

Dependent on HBX, HBV increased IL‐34 expression in hepatoma cells, and HBX upregulated and interacted with CEBP/α to enhance the activity of IL‐34 promoters. CEBP/α mediated by HBX was associated with the activation of PI3‐K and NF‐κB pathways to promote IL‐34 expression. Via CSF1‐R and CD138, IL‐34 promoted the proliferation and migration of hepatoma cells, and contributed to the activation of ERK and STAT3 pathways and the upregulation of Bcl‐xl and c‐Myc mediated by HBX.

Conclusion

We demonstrate that IL‐34 contributes to HBX‐mediated functional abnormality of HCC cells and provides a novel insight into the molecular mechanism of carcinogenesis mediated by HBX.

Immunomodulation of Interleukin-34 and its Potential Significance as a Disease Biomarker and Therapeutic Target

Interleukin (IL)-34 is a cytokine discovered a few years ago and identified as the second colony-stimulating factor (CSF)-1 receptor (CSF-1R) ligand. Although CSF-1 and IL-34 share the same receptor through which they trigger similar effects, IL-34 also binds to receptors protein-tyrosine phosphatase (PTP)-ζ and syndecan-1. Thus, IL-34 is involved in several signaling pathways and participates in a wide array of biological actions. This review analyzes current studies on the role of IL-34 under physiological and pathological conditions, and explores its potential significance as a disease biomarker and therapeutic target. In physiological conditions, IL-34 expression is restricted to the microglia and Langerhans cells, with a fundamental role in cellular differentiation, adhesion and migration, proliferation, metabolism, and survival. It is released in response to inflammatory stimuli, such as pathogen-associated molecular patterns or pro-inflammatory cytokines, with effects over various immune cells, including monocytes, macrophages, and regulatory T cells that shape the immune microenvironment. Over the past decade, accumulating evidence has suggested a potent immune regulation of IL-34 in pathological states such as autoimmune diseases, cancer, transplant rejection, neurologic diseases, infections, and inflammatory diseases. Importantly, IL-34 may hold great promise for acting as a biomarker for monitoring disease severity and progression, and may serve as a new therapeutic target for the treatment of several diseases in clinical settings.

MicroRNA-31 Negatively Regulates Interleukin-34 Expression In Vitro

Interleukin-34 (IL-34) is a recently discovered cytokine that promotes tissue macrophage maturation and differentiation. We previously found that 1α,25-Dihydroxyvitamin D3 up-regulated IL-34 expression in SH-SY5Y neural cells. However, whether microRNA regulates IL-34 expression is not completely clear. By using on-line TargetScan and MiRanda software, we found that there was only one conserved microRNA-31 (miR-31) binding site in the 3' untranslated region (3'UTR) of IL-34 mRNA. Intriguingly, using qPCR we demonstrated that miR-31 levels were negatively correlated to IL-34 mRNA levels in different cell lines. By examining the effect of miR-31 on IL-34 3' UTR reporter luciferase activity and on IL-34 mRNA and argonaute RISC catalytic component 2 (AGO2) binding, it was found that miR-31 bound directly to IL-34 3'UTR and regulated the post-transcriptional expression of IL-34 in MGC-803 cells. Moreover, a miR-31 mimic significantly reduced IL-34 expression levels while a miR-31 inhibitor up-regulated IL-34 expression in KYSE-45 and HT-29 cells. Taken together, these results show that miR-31 negatively regulates IL-34 expression by directly binding to the IL-34 3' UTR in vitro.

Interleukin-34, a comprehensive review

IL-34 is a novel cytokine that was identified in 2008 in a comprehensive proteomic analysis as a tissue-specific ligand of CSF-1 receptor (CSF-1R). IL-34 exists in all vertebrates including fish, amphibians, birds, and mammals, showing high conservation among species. Structurally, IL-34 belongs to the short-chain helical hematopoietic cytokine family but shows no apparent consensus structural domains, motifs, or sequence homology with other cytokines. IL-34 is synthesized as a secreted homodimeric glycoprotein that binds to the extracellular domains of CSF-1R and receptor-type protein-tyrosine phosphatase-zeta (PTP-ζ) in addition to the chondroitin sulfate chains of syndecan-1. These interactions result in activating several signaling pathways that regulate major cellular functions, including proliferation, differentiation, survival, metabolism, and cytokine/chemokine expression in addition to cellular adhesion and migration. In the steady state, IL-34 contributes to the development and maintenance of specific myeloid cell subsets in a tissue-specific manner: Langerhans cells in the skin and microglia in the brain. In pathological conditions, changes in IL-34 expression-increased or decreased-are involved in disease pathogenesis and correlate with progression, severity, and chronicity. One decade after its discovery, IL-34 has been introduced as a newcomer to the big family of interleukins with specific physiological functions, critical pathological roles, and promising clinical applications in disease diagnosis and treatment. In this review, we celebrate the 10th anniversary of IL-34 discovery, introducing its biological characteristics, and discussing the importance of IL-34 signaling network in health and disease.

IL-34 regulates IL-6 and IL-8 production in human lung fibroblasts via MAPK, PI3K-Akt, JAK and NF-κB signaling pathways

IL-34 plays diverse roles in disease due to its inflammatory and immunosuppressive properties. Elevated IL-34 expression has been observed in lung cancers and pulmonary infections although its role is unclear. We found that IL-34 addition to primary lung fibroblasts significantly promoted IL-6 and IL-8 expression in a dose and time dependent manner. These effects were reversed when JAK, NF-κB, Akt and p38 inhibitors were included before IL-34 addition. Protein phosphorylation in these pathways was also observed through western-blotting. Stimulation of human lung fibroblasts with IL-34 in combination with TNF-α, IL-17A and IL-4 enhanced inflammatory cytokine production. Our data confirmed the inflammatory effect of IL-34 on human lung fibroblasts and suggested that the IL-34/CSF-1R axis may be a novel therapeutic target in pulmonary disease.

Impact of pathological features of brain metastases in prognosis

AIM

To evaluate the prognostic value of tumor-infiltrating lymphocytes (TILs) and Ki67 in brain metastasis lesions, and the effect of adding them to variables of graded prognostic assessment score.

PATIENTS & METHODS

Clinicopathological information from 111 medical charts of brain metastasis patients was obtained, and TIL distribution (n = 84), Ki67 index (n = 79) and CD3 TIL (n = 64) were prospectively evaluated.

RESULTS

Most frequent TIL pattern was perivascular (67.8%), and median Ki67 and CD3 TIL percents were 30 and 4.8%, respectively. Ki67 ≥15 was associated with shorter survival (p = 0.018) but CD3 TIL was not (p = 0.870). The highest graded prognostic assessment score was not associated with survival (p = 0.648), however, those with low Ki67 and high score was associated with better outcome (p = 0.007).

CONCLUSION

High Ki67 index in brain metastasis carries a worse prognosis.

Recent advances in colony stimulating factor-1 receptor/c-FMS as an emerging target for various therapeutic implications

Colony stimulating factor-1 (CSF-1) is one of the most common proinflammatory cytokine responsible for various inflammatory disorders. It has a remarkable role in the development and progression of osteoarthritis, cancer and other autoimmune disease conditions. The CSF-1 acts by binding to the receptor, called colony stimulating factor-1 receptor (CSF-1R) also known as c-FMS resulting in the cascade of signalling pathway causing cell proliferation and differentiation. Interleukin-34 (IL-34), recently identified as another ligand for CSF-IR, is a cytokine protein. Both, CSF-1 and IL-34, although two distinct cytokines, follow the similar signalling pathway on binding to the same receptor, CSF-1R. Like CSF-1, IL-34 promotes the differentiation and survival of monocyte, macrophages and osteoclasts. This CSF-1R/c-FMS is over expressed in many cancers and on tumour associated macrophages, consequently, have been exploited as a drug target for promising treatment for cancer and inflammatory diseases. Some CSF-1R/c-FMS inhibitors such as ABT-869, Imatinib, AG013736, JNJ-40346527, PLX3397, DCC-3014 and Ki20227 have been successfully used in these disease conditions. Many c-FMS inhibitors have been the candidates of clinical trials, but suffer from some side effects like cardiotoxicity, vomiting, swollen eyes, diarrhoea, etc. If selectivity of cFMS inhibition is achieved successfully, side effects can be overruled and this approach may become a novel therapy for treatment of various therapeutic interventions. Thus, successful targeting of c-FMS may result in multifunctional therapy. With this background of information, the present review focuses on the recent developments in the area of CSF-1R/c-FMS inhibitors with emphasis on crystal structure, mechanism of action and various therapeutic implications in which c-FMS plays a pivotal role. The review on structure activity relationship of various compounds acting as the inhibitors of c-FMS which gives the selection criteria for the development of novel molecules is also being presented.

Enhanced IL-34 expression in Nivolumab-resistant metastatic melanoma

Background

Immunotherapies that target immune-checkpoint molecules such PD-1 have helped to achieve durable responses in melanoma treatment. However, 25% of melanoma patients who showed objective responses to PD-1 blockade develop resistance and suffer from disease progression and ultimately death, which necessitates the identification of related resistance mechanisms.

IL-34 is a cytokine that controls the biology of myeloid cell lineage through binding to CSF-1R. IL-34 is importantly involved in the pathogenesis of various diseases. In cancer, the expression of IL-34 has been suggested to associate with tumor growth, metastasis, angiogenesis, and therapeutic resistance such as in lung cancers and malignant pleural mesotheliomas. In this study, we evaluate the possible involvement of IL-34 in immunotherapeutic resistance.

Case presentation

Melanoma resection species were obtained from a patient who developed a refractory melanoma against immunotherapy with Nivolumab, and stained with anti-IL-34, anti-melanoma antigens and anti-CD163 antibody. Staining of these markers was compared between primary or metastatic refractory melanoma tissues. Immunohistochemistry staining of melanoma tissues showed an enhanced expression of IL-34 in metastatic refractory melanoma compared to primary melanoma tissues, which correlates with increased frequencies of CD163⁺ macrophages.

Conclusion

We introduce for the first time a clinical case of a patient with metastatic refractory melanoma that acquired resistance to anti-PD-1 immunotherapy, showing an enhanced expression of IL-34 in refractory melanoma tissues.

The roles of CSFs on the functional polarization of tumor-associated macrophages

Macrophages have a central role in numerous physiological processes, such as immune defense, maintenance of tissue homeostasis, wound healing, and inflammation. Moreover, in numerous severe disorders, such as cancer or chronic inflammation, their functions can be profoundly affected. Macrophages continuously sense their environment and adapt their phenotypes and functions to the local requirements; this process is called plasticity. In addition to stress signals, metabolites, and direct cell-contact interactions with surrounding cells, numerous cytokines play a central role in controlling macrophage polarization. In this review, we will focus on three human macrophage differentiation factors: macrophage colony-stimulating factor (M-CSF), IL-34, and granulocyte M-CSF. These CSFs allow human monocyte survival, promote their differentiation into macrophages, and control macrophage polarization as they give rise to cells with different phenotype and functions. Based on recent observations, the role of granulocyte CSF on macrophage polarization is also addressed. Finally, our current knowledge on the expression of these growth factors in tumor microenvironment and their impact on the generation and polarization of tumor-associated macrophages are summarized.

Interleukin 34, from pathogenesis to clinical applications

Interleukin-34 (IL-34) is a hematopoietic cytokine that was described for the first time in 2008 as a second ligand of CSF1R in addition to M-CSF. IL-34 and M-CSF share no sequence homology, but have similar functions, affecting the biology of myeloid cell lineage. In contrast to M-CSF, IL-34 shows unique signaling and expression patterns. Physiologically, IL-34 expression is restricted to epidermis and CNS, acting as a regulator of Langerhans cells and microglia, respectively. However, IL-34 expression can be induced and regulated by NF-κB under pathological conditions. Importantly, growing evidence indicates a correlation between IL-34 and disease severity, chronicity and progression. In addition to its promising roles as a novel diagnostic and prognostic biomarker of disease, IL-34 may also serve as a powerful target for therapeutic intervention. Here, we review the current knowledge regarding the emerging roles of IL-34 in disease, and focus on the clinical applications of IL-34 in medicine.

Immunoregulatory properties of the cytokine IL-34

Interleukin-34 is a cytokine with only partially understood functions, described for the first time in 2008. Although IL-34 shares very little homology with CSF-1 (CSF1, M-CSF), they share a common receptor CSF-1R (CSF-1R) and IL-34 has also two distinct receptors (PTP-ζ) and CD138 (syndecan-1). To make the situation more complex, IL-34 has also been shown as pairing with CSF-1 to form a heterodimer. Until now, studies have demonstrated that this cytokine is released by some tissues that differ to those where CSF-1 is expressed and is involved in the differentiation and survival of macrophages, monocytes, and dendritic cells in response to inflammation. The involvement of IL-34 has been shown in areas as diverse as neuronal protection, autoimmune diseases, infection, cancer, and transplantation. Our recent work has demonstrated a new and possible therapeutic role for IL-34 as a Foxp3+ Treg-secreted cytokine mediator of transplant tolerance. In this review, we recapitulate most recent findings on IL-34 and its controversial effects on immune responses and address its immunoregulatory properties and the potential of targeting this cytokine in human.

Molecular cloning, expression, IgE binding activities and in silico epitope prediction of Per a 9 allergens of the American cockroach

Per a 9 is a major allergen of the American cockroach (CR), which has been recognized as an important cause of imunoglobulin E-mediated type I hypersensitivity worldwide. However, it is not neasy to obtain a substantial quantity of this allergen for use in functional studies. In the present study, the Per a 9 gene was cloned and expressed in Escherichia coli (E. coli) systems. It was found that 13/16 (81.3%) of the sera from patients with allergies caused by the American CR reacted to Per a 9, as assessed by enzyme-linked immunosorbent assay, confirming that Per a 9 is a major allergen of CR. The induction of the expression of CD63 and CCR3 in passively sensitized basophils (from sera of patients with allergies caused by the American CR) by approximately 4.2-fold indicated that recombinant Per a 9 was functionally active. Three immunoinformatics tools, including the DNAStar Protean system, Bioinformatics Predicted Antigenic Peptides (BPAP) system and the BepiPred 1.0 server were used to predict the potential B cell epitopes, while Net-MHCIIpan-2.0 and NetMHCII-2.2 were used to predict the T cell epitopes of Per a 9. As a result, we predicted 11 peptides (23-28, 39-46, 58-64, 91-118, 131-136, 145-154, 159-165, 176-183, 290-299, 309-320 and 338-344) as potential B cell linear epitopes. In T cell prediction, the Per a 9 allergen was predicted to have 5 potential T cell epitope sequences, 119-127, 194-202, 210-218, 239-250 and 279-290. The findings of our study may prove to be useful in the development of peptide-based vaccines to combat CR-induced allergies.

Association of Sp1 and survivin in epithelial ovarian cancer: Sp1 inhibitor and cisplatin, a novel combination for inhibiting epithelial ovarian cancer cell proliferation

The expression of specificity protein 1 (Sp1) and survivin was evaluated in clinical specimens of epithelial ovarian cancer (EOC) patients. When compared to normal tissue, EOC samples showed high expression of Sp1 and survivin using qPCR (Sp1: ∼2-fold; survivin: ∼5-fold) and Western blot (Sp1: >2.6-fold; survivin: >100-fold). The Sp1 inhibitor, and anti-cancer small molecule, tolfenamic acid (TA), was tested to enhance the response of Cisplatin (Cis) in EOC cell lines. Cell viability (CellTiter-Glo), combination index (CalcuSyn software), apoptosis (Annexin-V staining), cell cycle analyses (flow cytometry), and reactive oxygen species (flow cytometry) were determined. Cell migration and invasion was assessed using matrigel coated transwell chambers. Agilent Technologies proteomics analysis identified potential signaling pathways involved. The combination of TA (50 μM) and Cis (5 μM) synergistically increased the growth inhibition in ES2 (∼80 %, p < 0.001) and OVCAR-3 (60 %, p < 0.001) cells. TA or TA + Cis treatment in ES2 cells caused cell cycle arrest in G1 Phase (TA) or S-Phase (TA + Cis) and unregulated reactive oxygen species. Invasion and migration was decreased in ES2 cells. Global proteomic profiling showed modulation of proteins associated with oxidative phosphorylation, apoptosis, electron transport chain, DNA damage, and cell cycle proteins. These results demonstrate an association of Sp1 and survivin in EOC and confirm targeting these candidates with TA potentially sensitizes EOC cells to cisplatin.

Identifying the role of Wilms tumor 1 associated protein in cancer prediction using integrative genomic analyses

The Wilms tumor suppressor, WT1 was first identified due to its essential role in the normal development of the human genitourinary system. Wilms tumor 1 associated protein (WTAP) was subsequently revealed to interact with WT1 using yeast two-hybrid screening. The present study identified 44 complete WTAP genes in the genomes of vertebrates, including fish, amphibians, birds and mammals. The vertebrate WTAP proteins clustered into the primate, rodent and teleost lineages using phylogenetic tree analysis. From 1,347 available SNPs in the human WTAP gene, 19 were identified to cause missense mutations. WTAP was expressed in bladder, blood, brain, breast, colorectal, esophagus, eye, head and neck, lung, ovarian, prostate, skin and soft tissue cancers. A total of 17 out of 328 microarrays demonstrated an association between WTAP gene expression and cancer prognosis. However, the association between WTAP gene expression and prognosis varied in distinct types of cancer, and even in identical types of cancer from separate microarray databases. By searching the Catalogue of Somatic Mutations in Cancer database, 65 somatic mutations were identified in the human WTAP gene from the cancer tissue samples. These results suggest that the function of WTAP in tumor formation may be multidimensional. Furthermore, signal transducer and activator of transcription 1, forkhead box protein O1, interferon regulatory factor 1, glucocorticoid receptor and peroxisome proliferator-activated receptor γ transcription factor binding sites were identified in the upstream (promoter) region of the human WTAP gene, suggesting that these transcription factors may be involved in WTAP functions in tumor formation.

Transcription factor RFX1 is ubiquitinated by E3 ligase STUB1 in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease caused by complex interactions between genes and the environment. The expression level of transcription factor regulatory factor X 1 (RFX1) is reduced in T cells from SLE patients. RFX1 can regulate epigenetic modifications of CD70 and CD11a and plays an important role in the development of SLE. However, the mechanisms that mediate reduction of RFX1 in SLE are unclear. Here, we demonstrate that RFX1 protein expression can be tightly regulated by polyubiquitination-mediated proteosomal degradation via STIP1 homology and U-box containing protein 1 (STUB1). The E3 ligase STUB1 is upregulated in CD4(+)T cells of SLE patients compared to healthy subjects. Overexpression of STUB1 in CD4(+)T cells leads to upregulation of levels of CD70 and CD11a in T cells. The modulation of STUB1 activity may provide a novel therapeutic approach for SLE.

Integrative genomic analysis of interleukin-36RN and its prognostic value in cancer

Interleukin (IL)-36RN, previously known as IL1-F5 and IL-1δ, shares a 360-kb region of chromosome 2q13 with members of IL-1 systems. IL-36RN encodes an anti-inflammatory cytokine, IL-36 receptor antagonist (IL-36Ra). In spite of IL-36Ra showing the highest homology to IL-1 receptor (IL-1R) antagonist, it differs from the latter in aspects including its binding to IL-lRrp2 but not to IL-1R1. IL-36RN is mainly expressed in epithelial cells and has important roles in inflammatory diseases. In the present study, IL-36RN was identified in the genomes of 27 species, including human, chimpanzee, mouse, horse and dolphin. Human IL-36RN was mainly expressed in the eye, head and neck, fetal heart, lung, testis, cervix and placenta; furthermore, it was highly expressed in bladder and parathyroid tumors. Furthermore, a total of 30 single nucleotide polymorphisms causing missense mutations were determined, which are considered to be the causes of various diseases, such as generalized pustular psoriasis. In addition, the link between IL-36RN and the prognosis of certain cancer types was revealed through meta-analysis. Tumor-associated transcriptional factors c-Fos, activator protein-1, c-Jun and nuclear factor κB were found to bind to the upstream region in the IL-36RN gene. This may indicate that IL-36RN is involved in tumorigenesis and tumor progression through the regulation of tumor-associated transcriptional factors. The present study identified IL-36RN in various species and investigated the associations between IL-36RN and cancer prognosis, which would determine whether IL-36RN drove the evolution of the various species with regard to tumorigenesis.

Integrative genomic analyses of the RNA-binding protein, RNPC1, and its potential role in cancer prediction

The RNA binding motif protein 38 (RBM38, also known as RNPC1) plays a pivotal role in regulating a wide range of biological processes, from cell proliferation and cell cycle arrest to cell myogenic differentiation. It was originally recognized as an oncogene, and was frequently found to be amplified in prostate, ovarian and colorectal cancer, chronic lymphocytic leukemia, colon carcinoma, esophageal cancer, dog lymphomas and breast cancer. In the present study, the complete RNPC1 gene was identified in a number of vertebrate genomes, suggesting that RNPC1 exists in all types of vertebrates, including fish, amphibians, birds and mammals. In the different genomes, the gene had a similar 4 exon/3 intron organization, and all the genetic loci were syntenically conserved. The phylogenetic tree demonstrated that the RNPC1 gene from the mammalian, bird, reptile and teleost lineage formed a species-specific cluster. A total of 34 functionally relevant single nucleotide polymorphisms (SNPs), including 14 SNPs causing missense mutations, 8 exonic splicing enhancer SNPs and 12 SNPs causing nonsense mutations, were identified in the human RNPC1 gene. RNPC1 was found to be expressed in bladder, blood, brain, breast, colorectal, eye, head and neck, lung, ovarian, skin and soft tissue cancer. In 14 of the 94 tests, an association between RNPC1 gene expression and cancer prognosis was observed. We found that the association between the expression of RNPC1 and prognosis varied in different types of cancer, and even in the same type of cancer from the different databases used. This suggests that the function of RNPC1 in these tumors may be multidimensional. The sex determining region Y (SRY)-box 5 (Sox5), runt-related transcription factor 3 (RUNX3), CCAAT displacement protein 1 (CUTL1), v-rel avian reticuloendotheliosis viral oncogene homolog (Rel)A, peroxisome proliferator-activated receptor γ isoform 2 (PPARγ2) and activating transcription factor 6 (ATF6) regulatory transcription factor binding sites were identified in the upstream (promoter) region of the RNPC1 gene, and may thus be involved in the effects of RNPC1 in tumors.