Signaling of type II oncostatin M receptor

Nonspecific Inhibition of IL6 Family Cytokine Signalling by Soluble gp130

IL6 is a proinflammatory cytokine that binds to membrane-bound IL6 receptor (IL6R) or soluble IL6R to signal via gp130 in cis or trans, respectively. We tested the hypothesis that sgp130Fc, which is believed to be a selective IL6 trans-signalling inhibitor, is in fact a non-specific inhibitor of gp130 signalling. In human cancer and primary cells, sgp130Fc inhibited IL6, IL11, OSM and CT1 cis-signalling. The IC50 values of sgp130Fc for IL6 and OSM cis-signalling were markedly (20- to 200-fold) lower than the concentrations of sgp130Fc used in mouse studies and clinical trials. sgp130 inhibited IL6 and OSM signalling in the presence of an ADAM10/17 inhibitor and the absence of soluble IL6R or OSMR, with effects that were indistinguishable from those of a gp130 neutralising antibody. These data show that sgp130Fc does not exclusively block IL6 trans-signalling and reveal instead that broad inhibition of gp130 signalling likely underlies its therapeutic effects. This proposes global or modular inhibition of gp130 as a therapeutic approach for treating human disease.

New perspectives in cancer immunotherapy: targeting IL-6 cytokine family

Chronic inflammation has been recognized as a canonical cancer hallmark. It is orchestrated by cytokines, which are master regulators of the tumor microenvironment (TME) as they represent the main communication bridge between cancer cells, the tumor stroma, and the immune system. Interleukin (IL)-6 represents a keystone cytokine in the link between inflammation and cancer. Many cytokines from the IL-6 family, which includes IL-6, oncostatin M, leukemia inhibitory factor, IL-11, IL-27, IL-31, ciliary neurotrophic factor, cardiotrophin 1, and cardiotrophin-like cytokine factor 1, have been shown to elicit tumor-promoting roles by modulating the TME, making them attractive therapeutic targets for cancer treatment.The development of immune checkpoint blockade (ICB) immunotherapies has radically changed the outcome of some cancers including melanoma, lung, and renal, although not without hurdles. However, ICB shows limited efficacy in other solid tumors. Recent reports support that chronic inflammation and IL-6 cytokine signaling are involved in resistance to immunotherapy. This review summarizes the available preclinical and clinical data regarding the implication of IL-6-related cytokines in regulating the immune TME and the response to ICB. Moreover, the potential clinical benefit of combining ICB with therapies targeting IL-6 cytokine members for cancer treatment is discussed.

Characterization of an Osmr Conditional Knockout Mouse Model

Oncostatin M (OSM) is a member of the interleukin-6 (IL-6) family of cytokines and has been found to have distinct anti-inflammatory and pro-inflammatory properties in various cellular and disease contexts. OSM signals through two receptor complexes, one of which includes OSMRβ. To investigate OSM-OSMRβ signaling in adult hematopoiesis, we utilized the readily available conditional Osmrfl/fl mouse model B6;129-Osmrtm1.1Nat/J, which is poorly characterized in the literature. This model contains loxP sites flanking exon 2 of the Osmr gene. We crossed Osmrfl/fl mice to interferon-inducible Mx1-Cre, which is robustly induced in adult hematopoietic cells. We observed complete recombination of the Osmrfl allele and loss of exon 2 in hematopoietic (bone marrow) as well as non-hematopoietic (liver, lung, kidney) tissues. Using a TaqMan assay with probes downstream of exon 2, Osmr transcript was lower in the kidney but equivalent in bone marrow, lung, and liver from Osmrfl/fl Mx1-Cre versus Mx1-Cre control mice, suggesting that transcript is being produced despite loss of this exon. Western blots show that liver cells from Osmrfl/fl Mx1-Cre mice had complete loss of OSMR protein, while bone marrow, kidney, and lung cells had reduced OSMR protein at varying levels. RNA-seq analysis of a subpopulation of bone marrow cells (hematopoietic stem cells) finds that some OSM-stimulated genes, but not all, are suppressed in Osmrfl/fl Mx1-Cre cells. Together, our data suggest that the B6;129-Osmrtm1.1Nat/J model should be utilized with caution as loss of Osmr exon 2 has variable and tissue-dependent impact on mRNA and protein expression.

Multifaceted oncostatin M: novel roles and therapeutic potential of the oncostatin M signaling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a self-immune inflammatory disease characterized by joint damage. A series of cytokines are involved in the development of RA. Oncostatin M (OSM) is a pleiotropic cytokine that primarily activates the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway, the mitogen-activated protein kinase (MAPK) signaling pathway, and other physiological processes such as cell proliferation, inflammatory response, immune response, and hematopoiesis through its receptor complex. In this review, we first describe the characteristics of OSM and its receptor, and the biological functions of OSM signaling. Subsequently, we discuss the possible roles of OSM in the development of RA from clinical and basic research perspectives. Finally, we summarize the progress of clinical studies targeting OSM for the treatment of RA. This review provides researchers with a systematic understanding of the role of OSM signaling in RA, which can guide the development of drugs targeting OSM for the treatment of RA.

The clinical relevance of OSM in inflammatory diseases: a comprehensive review

Oncostatin M (OSM) is a pleiotropic cytokine involved in a variety of inflammatory responses such as wound healing, liver regeneration, and bone remodeling. As a member of the interleukin-6 (IL-6) family of cytokines, OSM binds the shared receptor gp130, recruits either OSMRβ or LIFRβ, and activates a variety of signaling pathways including the JAK/STAT, MAPK, JNK, and PI3K/AKT pathways. Since its discovery in 1986, OSM has been identified as a significant contributor to a multitude of inflammatory diseases, including arthritis, inflammatory bowel disease, lung and skin disease, cardiovascular disease, and most recently, COVID-19. Additionally, OSM has also been extensively studied in the context of several cancer types including breast, cervical, ovarian, testicular, colon and gastrointestinal, brain,lung, skin, as well as other cancers. While OSM has been recognized as a significant contributor for each of these diseases, and studies have shown OSM inhibition is effective at treating or reducing symptoms, very few therapeutics have succeeded into clinical trials, and none have yet been approved by the FDA for treatment. In this review, we outline the role OSM plays in a variety of inflammatory diseases, including cancer, and outline the previous and current strategies for developing an inhibitor for OSM signaling.

Stimulation of Osteoclast Formation by Oncostatin M and the Role of WNT16 as a Negative Feedback Regulator

Oncostatin M (OSM), which belongs to the IL-6 family of cytokines, is the most potent and effective stimulator of osteoclast formation in this family, as assessed by different in vitro assays. Osteoclastogenesis induced by the IL-6 type of cytokines is mediated by the induction and paracrine stimulation of the osteoclastogenic cytokine receptor activator of nuclear factor κ-B ligand (RANKL), expressed on osteoblast cell membranes and targeting the receptor activator of nuclear factor κ-B (RANK) on osteoclast progenitor cells. The potent effect of OSM on osteoclastogenesis is due to an unusually robust induction of RANKL in osteoblasts through the OSM receptor (OSMR), mediated by a JAK-STAT/MAPK signaling pathway and by unique recruitment of the adapter protein Shc1 to the OSMR. Gene deletion of Osmr in mice results in decreased numbers of osteoclasts and enhanced trabecular bone caused by increased trabecular thickness, indicating that OSM may play a role in physiological regulation of bone remodeling. However, increased amounts of OSM, either through administration of recombinant protein or of adenoviral vectors expressing Osm, results in enhanced bone mass due to increased bone formation without any clear sign of increased osteoclast numbers, a finding which can be reconciled by cell culture experiments demonstrating that OSM can induce osteoblast differentiation and stimulate mineralization of bone nodules in such cultures. Thus, in vitro studies and gene deletion experiments show that OSM is a stimulator of osteoclast formation, whereas administration of OSM to mice shows that OSM is not a strong stimulator of osteoclastogenesis in vivo when administered to adult animals. These observations could be explained by our recent finding showing that OSM is a potent stimulator of the osteoclastogenesis inhibitor WNT16, acting in a negative feedback loop to reduce OSM-induced osteoclast formation.

Murine Oncostatin M Has Opposing Effects on the Proliferation of OP9 Bone Marrow Stromal Cells and NIH/3T3 Fibroblasts Signaling through the OSMR

The IL-6 family cytokine Oncostatin M (OSM) is involved in cell development, growth, hematopoiesis, inflammation, and cancer. Intriguingly, OSM has proliferative and antiproliferative effects depending on the target cell. The molecular mechanisms underlying these opposing effects are not fully understood. Previously, we found OSM upregulation in different myeloproliferative syndromes. However, OSM receptor (OSMR) expression was detected on stromal cells but not the malignant cells themselves. In the present study, we, therefore, investigated the effect of murine OSM (mOSM) on proliferation in stromal and fibroblast cell lines. We found that mOSM impairs the proliferation of bone marrow (BM) stromal cells, whereas fibroblasts responded to mOSM with increased proliferation. When we set out to reveal the mechanisms underlying these opposing effects, we detected increased expression of the OSM receptors OSMR and LIFR in stromal cells. Interestingly, Osmr knockdown and Lifr overexpression attenuated the OSM-mediated effect on proliferation in both cell lines indicating that mOSM affected the proliferation signaling mainly through the OSMR. Furthermore, mOSM induced activation of the JAK-STAT, PI3K-AKT, and MAPK-ERK pathways in OP9 and NIH/3T3 cells with differences in total protein levels between the two cell lines. Our findings offer new insights into the regulation of proliferation by mOSM.

Research Progress About Glioma Stem Cells in the Immune Microenvironment of Glioma

Gliomas are the most common primary tumors of the central nervous system. Due to the existence of the blood-brain barrier and its unique regional immune characteristics, the study of the immune microenvironment of gliomas is particularly important. Glioma stem cells are an important cause of initiating glioma, promoting tumor progression and leading to tumor recurrence. Immunotherapeutic strategies targeting glioma stem cells have become the focus of current research. This paper will focus on the research progress of glioma stem cells in the immune microenvironment of glioma to provide the basis for the immunotherapy of glioma.

Xmrks the Spot: Fish Models for Investigating Epidermal Growth Factor Receptor Signaling in Cancer Research

Studies conducted in several fish species, e.g., Xiphophorus hellerii (green swordtail) and Xiphophorus maculatus (southern platyfish) crosses, Oryzias latipes (medaka), and Danio rerio (zebrafish), have identified an oncogenic role for the receptor tyrosine kinase, Xmrk, a gene product closely related to the human epidermal growth factor receptor (EGFR), which is associated with a wide variety of pathological conditions, including cancer. Comparative analyses of Xmrk and EGFR signal transduction in melanoma have shown that both utilize STAT5 signaling to regulate apoptosis and cell proliferation, PI3K to modulate apoptosis, FAK to control migration, and the Ras/Raf/MEK/MAPK pathway to regulate cell survival, proliferation, and differentiation. Further, Xmrk and EGFR may also modulate similar chemokine, extracellular matrix, oxidative stress, and microRNA signaling pathways in melanoma. In hepatocellular carcinoma (HCC), Xmrk and EGFR signaling utilize STAT5 to regulate cell proliferation, and Xmrk may signal through PI3K and FasR to modulate apoptosis. At the same time, both activate the Ras/Raf/MEK/MAPK pathway to regulate cell proliferation and E-cadherin signaling. Xmrk models of melanoma have shown that inhibitors of PI3K and MEK have an anti-cancer effect, and in HCC, that the steroidal drug, adrenosterone, can prevent metastasis and recover E-cadherin expression, suggesting that fish Xmrk models can exploit similarities with EGFR signal transduction to identify and study new chemotherapeutic drugs.

Molecular Structure and Function of Janus Kinases: Implications for the Development of Inhibitors

Cytokines can trigger multiple signalling pathways, including Janus tyrosine kinases [JAK] and signal transducers and activators of transcription [STATS] pathways. JAKs are cytoplasmic proteins that, following the binding of cytokines to their receptors, transduce the signal by phosphorylating STAT proteins which enter the nuclei and rapidly target gene promoters to regulate gene transcription. Due to the critical involvement of JAK proteins in mediating innate and adaptive immune responses, these family of kinases have become desirable pharmacological targets in inflammatory diseases, including ulcerative colitis and Crohn's disease. In this review we provide an overview of the main cytokines that signal through the JAK/STAT pathway and the available in vivo evidence on mutant or deleted JAK proteins, and discuss the implications of pharmacologically targeting this kinase family in the context of inflammatory diseases.

Oncostatin M Plays a Critical Role in Survival after Acute Intestinal Ischemia: Reperfusion Injury

Background: Acute intestinal ischemia-reperfusion injury (AIIRI) is a devastating clinical condition relevant to multiple diseases processes, including sepsis, trauma, transplantation, and burns. An AIIRI is a contributor to the development of multiple organ dysfunction syndrome (MODS). Oncostatin M (OSM)/oncostatin M receptor (OSMR) signaling is an unrecognized and novel candidate pathway for the mediation of MODS. In this study, we hypothesized that OSM mediates the injury mechanism of AIIRI leading to MODS. Methods: Wild-type (WT) and OSMR-knockout (OSMR^-/-) C57BL/6 mice underwent AIIRI using a well-established model of selective occlusion of the superior mesenteric artery (SMA). Serum cytokine concentrations were measured using a multiplex detection system. Further tissue analysis was conducted with polymerase chain reaction, enzyme-linked immunosorbent assay, Western blots, and histologic review. Results: Survival was significantly higher in WT than in OSMR^-/- groups at 30 minutes of ischemia with 2 hours of reperfusion (100% versus 42.9%; P = 0.015). No significant differences in the degree of local intestinal injury was seen in the two groups. In contrast, the degree of lung injury, as evidenced by myeloperixodase activity, was lower in OSMR^-/- animals in the early AIIRI groups. There was a greater degree of renal dysfunction in OSMR^-/- mice. Oncostatin M mediated interleukin (IL)-10 upregulation, with WT animals having significantly lower IL-10 concentrations (52.04 ± 23.06 pg/mL versus 324.37 ± 140.35 pg/mL; P = 0.046). Conclusion: Oncostatin M signalling is essential during acute intestinal ischemia-reperfusion injury. An OSMR deficiency results in decreased early lung injury but increased renal dysfunction. There was a significantly increased mortality rate after AIIRI in mice with OSMR deficiency. Augmentation of OSM may be a novel immunomodulatory strategy for AIIRI.

Insight into adipokines to optimize therapeutic effects of stem cell for tissue regeneration

Stem cell therapy is considered as a promising regenerative medicine for repairing and treating damaged tissues and/or preventing various diseases. But there are still some obstacles such as low cell migration, poor stem cell engraftment and decreased cell survival that need to be overcome before transplantation. Therefore, a large body of studies has focused on improving the efficiency of stem cell therapy. For instance, preconditioning of stem cells has emerged as an effective strategy to reinforce therapeutic efficacy. Adipokines are signaling molecules, secreted by adipose tissue, which regulate a variety of biological processes in adipose tissue and other organs including the brain, liver, and muscle. In this review article, we shed light on the biological effects of some adipokines including apelin, oncostatin M, omentin-1 and vaspin on stem cell therapy and the most recent preclinical advances in our understanding of how these functions ameliorate stem cell therapy outcome.

Balancing STAT Activity as a Therapeutic Strategy

Driven by dysregulated IL-6 family member cytokine signaling in the tumor microenvironment (TME), aberrant signal transducer and activator of transcription (STAT3) and (STAT5) activation have been identified as key contributors to tumorigenesis. Following transformation, persistent STAT3 activation drives the emergence of mesenchymal/cancer-stem cell (CSC) properties, important determinants of metastatic potential and therapy failure. Moreover, STAT3 signaling within tumor-associated macrophages and neutrophils drives secretion of factors that facilitate metastasis and suppress immune cell function. Persistent STAT5 activation is responsible for cancer cell maintenance through suppression of apoptosis and tumor suppressor signaling. Furthermore, STAT5-mediated CD4+/CD25+ regulatory T cells (T_regs) have been implicated in suppression of immunosurveillance. We discuss these roles for STAT3 and STAT5, and weigh the attractiveness of different modes of targeting each cancer therapy. Moreover, we discuss how anti-tumorigenic STATs, including STAT1 and STAT2, may be leveraged to suppress the pro-tumorigenic functions of STAT3/STAT5 signaling.

Oncostatin M as a new diagnostic, prognostic and therapeutic target in inflammatory bowel disease (IBD)

Introduction: Given the high rate of primary and acquired resistance to current inflammatory bowel disease (IBD) treatments, novel drug targets and biomarkers that aid in therapeutic prediction are eagerly awaited. Furthermore, postponing treatment initiation because of a diagnostic delay profoundly affects patient well-being and overall disease evolution. Among the emerging targets and biomarkers, oncostatin M (OSM) has gained much interest in the past few years.Areas covered: A literature search to June 2019 was performed to identify the most relevant reports on Oncostatin M. The authors summarize the biology of OSM, its role in health and disease, its potential as a diagnostic, prognostic and therapeutic biomarker in the field of IBD and how it might be a drug target of the future.Expert opinion: OSM has diagnostic, prognostic and therapeutic capabilities. High mucosal OSM predicts primary non-response to anti-TNF antibodies. However, one could question whether a single cytokine can capture the complexity and heterogeneity of IBD. Neutralizing OSM in patients with elevated mucosal OSM appears to be attractive and should be considered as a valid option for the first biomarker-stratified, proof-of-concept trial that studies a novel therapeutic compound in IBD.

ER stress abrogates the immunosuppressive effect of IL-10 on human macrophages through inhibition of STAT3 activation

Objective and design

To determine whether ER stress affects the inhibitory pathways of the human immune system, particularly the immunosuppressive effect of IL-10 on macrophages.

Material or subjects

In vitro stimulation of human monocyte-derived macrophages.

Treatment

Cells were stimulated with TLR ligands and IL-10, while ER stress was induced using thapsigargin or tunicamycin.

Methods

mRNA expression was determined using qPCR, while cytokine protein production was measured using ELISA. Protein expression of receptors and transcription factors was determined using flow cytometry. Student’s t test was used for statistics.

Results

While under normal conditions IL-10 potently suppresses pro-inflammatory cytokine production by LPS-stimulated macrophages, we demonstrate that ER stress counteracts the immunosuppressive effects of IL-10, leading to increased pro-inflammatory cytokine production. We identified that ER stress directly interferes with IL-10R signaling by reducing STAT3 phosphorylation on Tyr705, which thereby inhibits the expression of SOCS3. Moreover, we show that ER stress also inhibits STAT3 activation induced by other receptors such as IL-6R.

Conclusions

Combined, these data uncover a new general mechanism by which ER stress promotes inflammation. Considering its potential involvement in the pathogenesis of diseases such as Crohn’s disease and spondyloarthritis, targeting of this mechanism may provide new opportunities to counteract inflammation.

OSMR gene effect on the pathogenesis of chronic autoimmune Urticaria via the JAK/STAT3 pathway

Background

Chronic autoimmune urticaria (CAU) is a common skin disease and remains unclear understanding of pathogenesis in the vast majority of cases. In order to explore a new therapy for CAU, the current study was performed to investigate the possible functioning of the Oncostatin M receptor (OSMR) gene in the autoimmunity of CAU via regulation of the JAK/STAT3 signaling pathway.

Methods

CAU skin tissues from 24 CAU patients and normal skin tissues from normal subjects were collected. Hematoxylin-eosin (HE) staining was conducted to count eosinophils, and immunohistochemistry was carried out to detect the positive rate of OSMR expression in two kinds of skin tissues. A total of 72 Kunming (KM) mice were selected, and 60 mice were used for establishing CAU models and later transfected with different plasmids. The expression of inflammatory factors was evaluated by enzyme-linked immunosorbent assays (ELISA). Expressions of janus kinase (JAK), signal transducer and activator of transcription 3 (STAT3), interferon-stimulated gene 15 (ISG15), CT10-regulated kinase (CRK), and interferon regulatory factor 9 (IRF9) were identified using Western blot assay and reverse transcription quantitative polymerase chain reaction (RT-qPCR). Epithelial cell proliferation was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, and cell cycle distribution and cell apoptosis were assessed using flow cytometry.

Results

The findings confirm that OSMR protein expression and histamine release rate are highly elevated in human CAU skin tissues, and the expression of the JAK/STAT3 signaling pathway-related genes (OSMR, JAK2, STAT3, ISG15, CRK and IRF9) was up-regulated. OSMR gene silencing in CAU mice significantly decreases the content of inflammatory factors (IL-1, IL-6, IFN-γ, and IgE), the number of eosinophils, and reduces the expression of the JAK/STAT3 signaling pathway related genes, and further enhances cell proliferation, promotes cell cycle entry and inhibits apoptosis of epithelial cells.

Conclusion

All aforementioned results indicate that OSMR gene silencing inhibits the activation of the JAK/STAT3 signaling pathway, thereby suppressing the development of CAU.

The AB loop and D-helix in binding site III of human Oncostatin M (OSM) are required for OSM receptor activation

Oncostatin M (OSM) and leukemia inhibitory factor (LIF) are closely related members of the interleukin-6 (IL-6) cytokine family. Both cytokines share a common origin and structure, and both interact through a specific region, termed binding site III, to activate a dimeric receptor complex formed by glycoprotein 130 (gp130) and LIF receptor (LIFR) in humans. However, only OSM activates the OSM receptor (OSMR)-gp130 complex. The molecular features that enable OSM to specifically activate the OSMR are currently unknown. To define specific sequence motifs within OSM that are critical for initiating signaling via OSMR, here we generated chimeric OSM-LIF cytokines and performed alanine-scanning experiments. Replacement of the OSM AB loop within OSM's binding site III with that of LIF abrogated OSMR activation, measured as STAT3 phosphorylation at Tyr-705, but did not compromise LIFR activation. Correspondingly, substitution of the AB loop and D-helix in LIF with their OSM counterparts was sufficient for OSMR activation. The alanine-scanning experiments revealed that residues Tyr-34, Gln-38, Gly-39, and Leu-45 (in the AB loop) and Pro-153 (in the D-helix) had specific roles in activating OSMR but not LIFR signaling, whereas Leu-40 and Cys-49 (in the AB loop), and Phe-160 and Lys-163 (in the D-helix) were required for activation of both receptors. Because most of the key amino acid residues identified here are conserved between LIF and OSM, we concluded that comparatively minor differences in a few amino acid residues within binding site III account for the differential biological effects of OSM and LIF.

Interferon-γ is a master checkpoint regulator of cytokine-induced differentiation

Cytokines are protein mediators that are known to be involved in many biological processes, including cell growth, survival, inflammation, and development. To study their regulation, we generated a library of 209 different cytokines. This was used in a combinatorial format to study the effects of cytokines on each other, with particular reference to the control of differentiation. This study showed that IFN-γ is a master checkpoint regulator for many cytokines. It operates via an autocrine mechanism to elevate STAT1 and induce internalization of gp130, a common component of many heterodimeric cytokine receptors. This targeting of a receptor subunit that is common to all members of an otherwise diverse family solves the problem of how a master regulator can control so many diverse receptors. When one adds an autocrine mechanism, fine control at the level of individual cells is achieved.

Functional proteogenomics reveals biomarkers and therapeutic targets in lymphomas

Identification of biomarkers and therapeutic targets is a critical goal of precision medicine. N-glycoproteins are a particularly attractive class of proteins that constitute potential cancer biomarkers and therapeutic targets for small molecules, antibodies, and cellular therapies. Using mass spectrometry (MS), we generated a compendium of 1,091 N-glycoproteins (from 40 human primary lymphomas and cell lines). Hierarchical clustering revealed distinct subtype signatures that included several subtype-specific biomarkers. Orthogonal immunological studies in 671 primary lymphoma tissue biopsies and 32 lymphoma-derived cell lines corroborated MS data. In anaplastic lymphoma kinase-positive (ALK⁺) anaplastic large cell lymphoma (ALCL), integration of N-glycoproteomics and transcriptome sequencing revealed an ALK-regulated cytokine/receptor signaling network, including vulnerabilities corroborated by a genome-wide clustered regularly interspaced short palindromic screen. Functional targeting of IL-31 receptor β, an ALCL-enriched and ALK-regulated N-glycoprotein in this network, abrogated ALK⁺ALCL growth in vitro and in vivo. Our results highlight the utility of functional proteogenomic approaches for discovery of cancer biomarkers and therapeutic targets.

STAT3-mediated SMAD3 activation underlies Oncostatin M-induced Senescence

Cytokines in the developing tumor microenvironment (TME) can drive transformation and subsequent progression toward metastasis. Elevated levels of the Interleukin-6 (IL-6) family cytokine Oncostatin M (OSM) in the breast TME correlate with aggressive, metastatic cancers, increased tumor recurrence, and poor patient prognosis. Paradoxically, OSM engages a tumor-suppressive, Signal Transducer and Activator of Transcription 3 (STAT3)-dependent senescence response in normal and non-transformed human mammary epithelial cells (HMEC). Here, we identify a novel link between OSM-activated STAT3 signaling and the Transforming Growth Factor-β (TGF-β) signaling pathway that engages senescence in HMEC. Inhibition of functional TGF-β/SMAD signaling by expressing a dominant-negative TGF-β receptor, treating with a TGF-β receptor inhibitor, or suppressing SMAD3 expression using a SMAD3-shRNA prevented OSM-induced senescence. OSM promoted a protein complex involving activated-STAT3 and SMAD3, induced the nuclear localization of SMAD3, and enhanced SMAD3-mediated transcription responsible for senescence. In contrast, expression of MYC (c-MYC) from a constitutive promoter abrogated senescence and strikingly, cooperated with OSM to promote a transformed phenotype, epithelial-mesenchymal transition (EMT), and invasiveness. Our findings suggest that a novel STAT3/SMAD3-signaling axis is required for OSM-mediated senescence that is coopted during the transformation process to confer aggressive cancer cell properties. Understanding how developing cancer cells bypass OSM/STAT3/SMAD3-mediated senescence may help identify novel targets for future "pro-senescence" therapies aiming to reengage this hidden tumor-suppressive response.

Stabilization of Oncostatin-M mRNA by Binding of Nucleolin to a GC-Rich Element in Its 3'UTR

Oncostatin-M (OSM) is a patho-physiologically important pleiotropic, multifunctional cytokine. OSM mRNA sequence analysis revealed that its 3'UTR contains three highly conserved GC-rich cis-elements (GCREs) whose role in mRNA stability is unidentified. In the present study, the functional role of the proximal GC-rich region of osm 3'-UTR (GCRE-1) in post-transcriptional regulation of osm expression in U937 cells was assessed by transfecting construct containing GCRE-1 at 3'-end of a fairly stable reporter gene followed by analysis of the expression of the reporter. GCRE-1 showed mRNA destabilizing activity; however, upon PMA treatment the reporter message containing GCRE-1 was stabilized. This stabilization is owing to a time-dependent progressive binding of trans-factors (at least five proteins) to GCRE-1 post-PMA treatment. Nucleolin was identified as one of the proteins in the RNP complex of GCRE-1 with PMA-treated U937 cytosolic extracts by oligo-dT affinity chromatography of poly-adenylated GCRE-1. Immuno-blot revealed time-dependent enhancement of nucleolin in the cytoplasm which in turn directly binds GCRE-1. RNA co-immunoprecipitation confirmed the GCRE-1-nucleolin interaction in vivo. To elucidate the functional role of nucleolin in stabilization of osm mRNA, nucleolin was overexpressed in U937 cells and found to stabilize the intrinsic osm mRNA, where co-transfection with the reporter containing GCRE-1 confirms the role of GCRE-1 in stabilization of the reporter mRNA. Thus, in conclusion, the results asserted that PMA treatment in U937 cells leads to cytoplasmic translocation of nucleolin that directly binds GCRE-1, one of the major GC-rich instability elements, thereby stabilizing the osm mRNA.

Oncostatin M induces IL-33 expression in liver endothelial cells in mice and expands ST2+CD4+ lymphocytes

Interleukin (IL)-33 is crucially involved in liver pathology and drives hepatoprotective functions. However, the regulation of IL-33 by cytokines of the IL-6 family, including oncostatin M (OSM) and IL-6, is not well studied. The aim of the present study was to determine whether OSM mediates regulation of IL-33 expression in liver cells. Intramuscular administration in mice of an adenovirus encoding OSM (AdOSM) leads to increase in expression of OSM in muscles, liver, and serum of AdOSM-infected mice compared with control mice. The increase of circulating OSM markedly regulated mRNA of genes associated with blood vessel biology, chemotaxis, cellular death, induction of cell adhesion molecules, and the alarmin cytokine IL-33 in liver. Steady-state IL-33 mRNA was upregulated by OSM at an early phase (8 h) following AdOSM infection. At the protein level, the expression of IL-33 was significantly induced in liver endothelial cells [liver sinusoidal endothelial cells (LSEC) and vascular endothelial cells] with a peak at 8 days post-AdOSM infection in mice. In addition, we found OSM-stimulated human microvascular endothelial HMEC-1 cells and human LSEC/TRP3 cells showed a significant increase in expression of IL-33 mRNA in a dose-dependent manner in cell culture. The OSM-mediated overexpression of IL-33 was associated with the activation/enrichment of CD4(+)ST2(+) cells in liver of AdOSM-infected mice compared with adenovirus encoding green fluorescent protein-treated control mice. In summary, these data suggest that the cytokine OSM regulates the IL-33 expression in liver endothelial cells in vivo and in HMEC-1/TRP3 cells in vitro and may specifically expand the target CD4(+)ST2(+) cells in liver.

Characterization of the CD40L/Oncostatin M/Oncostatin M receptor axis as an antiviral and immunostimulatory system disrupted in chronic HCV infection

BACKGROUND & AIMS

Oncostatin M (OSM) is an inflammatory cytokine which interacts with a heterodimeric receptor formed by gp130 and either OSMRβ or LIFR. Here we have analysed OSM and its receptors in livers with chronic hepatitis C (CHC) and studied the factors that regulate this system.

METHODS

OSM, OSM receptors and OSM-target molecules were studied by immunohistochemistry and/or qPCR analysis in livers from CHC patients and controls. We determined the production of OSM by CD40L-stimulated antigen presenting cells (APC) and its biological effects on HuH7 cells containing HCV replicon (HuH7 Core-3').

RESULTS

OSM was upregulated in livers with CHC and its production was mapped to CD11c+ cells. OSM levels correlated directly with inflammatory activity and CD40L expression. In vitro studies showed that OSM is released by APC upon interaction with activated CD4+ T cells in a CD40L-dependent manner. Culture of HuH7 Core-3' cells with supernatant from CD40L-stimulated APC repressed HCV replication and induced IL-7 and IL-15Rα. These effects were dampened by antibodies blocking OSM or gp130 and by silencing OSMRβ. In CHC livers OSMRβ and LIFR were significantly downregulated and their values correlated with those of OSM-induced molecules. Experiments in HuH7 cells showed that impaired STAT3 signaling and exposure to TGFβ1, two findings in CHC, are factors involved in repressing OSMRβ and LIFR, respectively.

CONCLUSIONS

OSM is a cytokine possessing vigorous antiviral and immunostimulatory properties which is released by APC upon interaction with CD40L present on activated CD4+ T cells. In livers with CHC, OSM is overexpressed but its biological activity appears to be hampered because of downregulation of its receptor subunits.

The enigmatic cytokine oncostatin m and roles in disease

Oncostatin M is a secreted cytokine involved in homeostasis and in diseases involving chronic inflammation. It is a member of the gp130 family of cytokines that have pleiotropic functions in differentiation, cell proliferation, and hematopoetic, immunologic, and inflammatory networks. However, Oncostatin M also has activities novel to mediators of this cytokine family and others and may have fundamental roles in mechanisms of inflammation in pathology. Studies have explored Oncostatin M functions in cancer, bone metabolism, liver regeneration, and conditions with chronic inflammation including rheumatoid arthritis, lung and skin inflammatory disease, atherosclerosis, and cardiovascular disease. This paper will review Oncostatin M biology in a historical fashion and focus on its unique activities, in vitro and in vivo, that differentiate it from other cytokines and inspire further study or consideration in therapeutic approaches.

gp130 activation is regulated by D2–D3 interdomain connectivity

Activation of the IL-6 (interleukin 6) receptor subunit gp130 (glycoprotein 130) has been linked to the formation of complexes with IL-6 and the IL-6 receptor, as well as to gp130 dimerization. However, it has been shown that gp130 is present as a pre-formed dimer, indicating that its activation is not solely dependent on dimerization. Therefore the detailed mechanism of gp130 activation still remains to be deciphered. Recently, deletion mutations of gp130 have been found in inflammatory hepatocellular adenoma. The mutations clustered around one IL-6-binding epitope of gp130 and resulted in a ligand-independent constitutively active gp130. We therefore hypothesized that conformational changes of this particular IL-6-binding epitope precedes gp130 activation. Using a rational structure-based approach we identified for the first time amino acids critical for gp130 activation. We can show that gp130 D2–D3 interdomain connectivity by hydrophobic residues stabilizes inactive gp130 conformation. Conformational destabilization of the EF loop present in domain D2 and disruption of D2–D3 hydrophobic interactions resulted in ligand-independent gp130 activation. Furthermore we show that the N-terminal amino acid residues of domain D1 participate in the activation of the gp130 deletion mutants. Taken together we present novel insights into the molecular basis of the activation of a cytokine receptor signalling subunit.

A unique loop structure in oncostatin M determines binding affinity toward oncostatin M receptor and leukemia inhibitory factor receptor

Oncostatin M (OSM) and leukemia inhibitory factor are pleiotropic cytokines that belong to the interleukin-6 (IL-6) family. These cytokines play a crucial role in diverse biological events like inflammation, neuroprotection, hematopoiesis, metabolism, and development. The family is grouped together based on structural similarities and their ability to activate the transmembrane receptor glycoprotein 130 (gp130). The common structure among these cytokines defines the spacing and the orientation of binding sites for cell surface receptors. OSM is unique in this family as it can signal using heterodimers of gp130 with either leukemia inhibitory factor receptor (LIFR) (type I) or oncostatin M receptor (OSMR) (type II). We have identified a unique helical loop on OSM between its B and C helices that is not found on other IL-6 family cytokines. This loop is located near the "FXXK" motif in active site III, which is essential for OSM's binding to both LIFR and OSMR. In this study, we show that the BC loop does not play a role in OSM's unique ability to bind OSMR. Shortening of the loop enhanced OSM's interaction with OSMR and LIFR as shown by kinetic and equilibrium binding analysis, suggesting the loop may hinder receptor interactions. As a consequence of improved binding, these structurally modified OSMs exhibited enhanced biological activity, including suppressed proliferation of A375 melanoma cells.

Oncostatin M induces heat hypersensitivity by gp130-dependent sensitization of TRPV1 in sensory neurons

Oncostatin M (OSM) is a member of the interleukin-6 cytokine family and regulates eg. gene activation, cell survival, proliferation and differentiation. OSM binds to a receptor complex consisting of the ubiquitously expressed signal transducer gp130 and the ligand binding OSM receptor subunit, which is expressed on a specific subset of primary afferent neurons. In the present study, the effect of OSM on heat nociception was investigated in nociceptor-specific gp130 knock-out (SNS-gp130^-/-) and gp130 floxed (gp130^fl/fl) mice.

Subcutaneous injection of pathophysiologically relevant concentrations of OSM into the hind-paw of C57BL6J wild type mice significantly reduced paw withdrawal latencies to heat stimulation. In contrast to gp130^fl/fl mice, OSM did not induce heat hypersensitivity in vivo in SNS-gp130^-/- mice. OSM applied at the receptive fields of sensory neurons in in vitro skin-nerve preparations showed that OSM significantly increased the discharge rate during a standard ramp-shaped heat stimulus. The capsaicin- and heat-sensitive ion channel TRPV1, expressed on a subpopulation of nociceptive neurons, has been shown to play an important role in inflammation-induced heat hypersensitivity. Stimulation of cultured dorsal root ganglion neurons with OSM resulted in potentiation of capsaicin induced ionic currents. In line with these recordings, mice with a null mutation of the TRPV1 gene did not show any signs of OSM-induced heat hypersensitivity in vivo.

The present data suggest that OSM induces thermal hypersensitivity by directly sensitizing nociceptors via OSMR-gp130 receptor mediated potentiation of TRPV1.

Development and utilization of activated STAT3 detection assays for screening a library of secreted proteins

Interleukin-6 (IL-6) family of cytokines are multifunctional proteins that play an important role in host defenses, acute phase reactions, immune responses, hematopoiesis, and tumorigenesis. The cytokines are produced by various lymphoid and nonlymphoid cells and mediate their biological activity through initial low-affinity binding to cell surface receptors, which are specific for their respective ligands. Ligand-specific receptor binding results in the receptor heterodimerization with ubiquitously expressed signal-transducing transmembrane component gp130 followed by activation of the gp130-associated Janus kinase, which, in turn, phosphorylates signal transducer and activator of transcription 3 (STAT3). Phosphorylated STAT3 (pSTAT3) dimerizes and translocates to the nucleus, where it activates gene transcription. Activation of STAT3 is essential to IL-6 family-associated physiological effects. Therefore, the ability to assess STAT3 phosphorylation is important for drug discovery efforts targeting IL-6 family cytokines. Various reagents and technologies are available to detect the effect of IL-6 type cytokines in treated cells. The present study describes the development of two pSTAT3 detection assays: the high-throughput screening assay based on Meso-Scale Discovery technology, which utilizes electrochemoluminescent signal measurements for the detection of pSTAT3 in treated cell extracts, and the secondary characterization assay based on fluorescent imaging analysis, which monitors pSTAT3 nuclear translocation in cells after activation. We have successfully utilized these assays to screen a small library of secreted proteins and identified inducers of STAT3 phosphorylation. The results obtained in this study demonstrate that both assays are robust, reliable, and amenable to high-throughput screening applications.

Neutral evolution on mammalian protein surfaces

Because of their low effective population sizes, natural selection is expected to have reduced effectiveness in organisms such as mammals. By comparing the amino acid substitution rates between mammalian protein surfaces and interiors, it was found that almost a third of the proteins surveyed failed to reject the null hypothesis of neutral substitutions among surface residues. Proteins with such partly neutral evolution nonetheless have no fewer protein interactions than do other proteins. I suggest that natural selection can function to preserve protein interactions without requiring strict conservation of the individual residue contacts that impart those interactions.

Long term oncostatin M treatment induces an osteocyte-like differentiation on osteosarcoma and calvaria cells

Previous in vitro studies on primary osteoblastic and osteosarcoma cells (normal and transformed osteoblasts) have shown that oncostatin M (OSM), a member of the interleukin-6 family, possesses cytostatic and pro-apoptotic effects in association with complex and poorly understood activities on osteoblast differentiation. In this study, we use rat osteosarcoma cells transduced with lentiviral particles encoding OSM (lvOSM) to stably produce this cytokine. We show that after several weeks of culture, transduced OSRGA and ROS 17/2.8 cells are growth inhibited and sensitized to apoptosis induced by the kinase inhibitor Staurosporine (Sts). Moreover, this long term OSM treatment induces (i) a decrease in osteoblastic markers, (ii) morphological changes leading to an elongated and/or stellate shape and (iii) an increase in osteocytic markers (sclerostin and/or E11), suggesting an osteocyte-like differentiation. We also show that non transformed rat calvaria cells transduced with lvOSM differentiate into stellate shaped cells expressing sclerostin, E11, Phex and functional hemichannels. Together, these results indicate that osteosarcoma cells stably producing OSM do not develop resistance to this cytokine and thus could be a valuable new tool to study the anti-cancer effect of OSM in vivo. Moreover, OSM-over-expressing osteoblastic cells differentiate into osteocyte-like cells, the major cellular contingent in bone, providing new culture conditions for this cell type which is difficult to obtain in vitro.

Oncostatin M enhances the antiviral effects of type I interferon and activates immunostimulatory functions in liver epithelial cells

Oncostatin M (OSM) is released together with type I interferon (IFN) by activated dendritic cells, suggesting a concerted action of these cytokines in the biological response against infection. We found that OSM increases the antiviral effect of IFN-alpha in Huh7 hepatoma cells infected with hepatitis A or hepatitis C virus and synergizes with IFN-alpha in the induction of antiviral genes. The combination of OSM and IFN-alpha led to upregulation of both STAT1 and STAT3 together with intense and prolonged activation of STAT1, STAT3, and Jak1. OSM with or without IFN-alpha also activated p38 mitogen-activated protein kinase, which is known to enhance transcription of IFN-alpha-inducible genes. Interestingly, OSM combined with IFN-alpha strongly induced immunoproteasome genes and other genes involved in antigen processing and presentation. Moreover, OSM, alone or in combination with IFN-alpha, upregulated relevant innate immunity molecules and increased the expression of intracellular adhesion molecule 1 and interleukin-15 receptor alpha (IL-15Ralpha) in liver cells. Hepatoma cells transfected with a plasmid encoding a viral antigen were able to activate effector T cells when pretreated with IFN-alpha plus OSM but not with each cytokine separately. Also, OSM, more than IFN-alpha, augmented the ability of Huh7 cells to transpresent IL-15 to responding lymphocytes and increased the immunostimulatory activity of liver epithelial cells by presenting a short viral peptide to sensitized cytotoxic T cells. In conclusion, OSM enhances the antiviral effects of type I interferon and cooperates with it in the induction of adaptive immune responses to pathogens. These findings may have therapeutic implications.

A dual role for oncostatin M signaling in the differentiation and death of mammary epithelial cells in vivo

Recent studies in breast cancer cell lines have shown that oncostatin M (OSM) not only inhibits proliferation but also promotes cell detachment and enhances cell motility. In this study, we have looked at the role of OSM signaling in nontransformed mouse mammary epithelial cells in vitro using the KIM-2 mammary epithelial cell line and in vivo using OSM receptor (OSMR)-deficient mice. OSM and its receptor were up-regulated approximately 2 d after the onset of postlactational mammary regression, in response to leukemia inhibitory factor (LIF)-induced signal transducer and activator of transcription-3 (STAT3). This resulted in sustained STAT3 activity, increased epithelial apoptosis, and enhanced clearance of epithelial structures during the remodeling phase of mammary involution. Concurrently, OSM signaling precipitated the dephosphorylation of STAT5 and repressed expression of the milk protein genes beta-casein and whey acidic protein (WAP). Similarly, during pregnancy, OSM signaling suppressed beta-casein and WAP gene expression. In vitro, OSM but not LIF persistently down-regulated phosphorylated (p)-STAT5, even in the continued presence of prolactin. OSM also promoted the expression of metalloproteinases MMP3, MMP12, and MMP14, which, in vitro, were responsible for OSM-specific apoptosis. Thus, the sequential activation of IL-6-related cytokines during mammary involution culminates in an OSM-dependent repression of epithelial-specific gene expression and the potentiation of epithelial cell extinction mediated, at least in part, by the reciprocal regulation of p-STAT5 and p-STAT3.

Box 2 region of the oncostatin M receptor determines specificity for recruitment of Janus kinases and STAT5 activation

Human and murine oncostatin M (OSM) induce their bioactivities through a heterodimeric receptor complex consisting of gp130 and the OSM receptor (OSMR), which initiates a signaling pathway involving Janus kinases (JAKs) and transcription factors of the signal transducers and activators of transcription (STAT) family. In contrast to the signal transducing receptor subunit gp130, the OSMR allows strong activation of STAT5B. The underlying molecular mechanism, however, remained unclear. Here we demonstrate that the human and murine OSM receptors use distinct mechanisms for STAT5B activation. The human receptor contains a STAT5B recruiting tyrosine motif (Tyr837/Tyr839) C-terminal to the box 1/2 region, which is absent in the mouse receptor. In contrast, the murine receptor initiates STAT5 activation directly via the receptor bound Janus kinases. Intriguingly, the murine receptor preferentially recruits JAK2, whereas the human receptor seems to have a higher affinity for JAK1. We identify a single amino acid (Phe820) in the human receptor that is responsible for this preference. Exchange by the murine counterpart (Cys815) allows recruitment of JAK2 by the human receptor and consequently activation of STAT5B independently of receptor tyrosine motifs. STAT5B interacts directly with JAK2 only in response to activation of the murine OSMR or the mutated human OSMR. Additionally, we show that OSM-induced STAT1 phosphorylation occurs independently of receptor tyrosine motifs and is mediated directly by Janus kinases, whereas the two C-terminally located tyrosine residues Tyr917/Tyr945 of the OSMR are crucial for STAT3 activation.

Stat5 as a diagnostic marker for leukemia

The Jak-Stat-Socs pathway is an important component of cytokine receptor signaling. Not surprisingly, perturbation of this pathway is implicated in diseases of hematopoietic and immune origin, including leukemia, lymphoma and immune deficiencies. This review examines the role of a key component of this pathway, Stat5. This has been shown to be activated in a variety of leukemias and myeloproliferative disorders, including downstream of a range of key oncogenes where it has been shown to play an important role in mediating their effects. Therefore, Stat5 represents a useful pan-leukemia/myeloproliferative disorder diagnostic marker and key therapeutic end point, as well as representing an attractive therapeutic target for these disorders.

Oncostatin-M inhibits luteinizing hormone stimulated Leydig cell progenitor formation in vitro

BACKGROUND

The initial steps of stem Leydig cell differentiation into steroid producing progenitor cells are thought to take place independent of luteinizing hormone (LH), under the influence of locally produced factors such as leukaemia inhibitory factor (LIF), platelet derived growth factor A and stem cell factor. For the formation of a normal sized Leydig cell population in the adult testis, the presence of LH appears to be essential. Oncostatin M (OSM) is a multifunctional cytokine and member of the interleukin (IL)-6 family that also includes other cytokines such as LIF. In the rat OSM is highly expressed in the late fetal and neonatal testis, and may thus be a candidate factor involved in Leydig cell progenitor formation.

METHODS

Interstitial cells were isolated from 13-day-old rat testes and cultured for 1, 3 or 8 days in the presence of different doses of OSM (range: 0.01 to 10 ng/ml) alone or in combination with LH (1 ng/ml). The effects of OSM and LH on cell proliferation were determined by incubating the cultures with [3H]thymidine or bromodeoxyuridine (BrdU). Developing progenitor cells were identified histochemically by the presence of the marker enzyme 3beta-hydroxysteroid dehydrogenase (3beta-HSD).

RESULTS

OSM, when added at a dose of 10 ng/ml, caused a nearly 2-fold increase in the percentage of Leydig cell progenitors after 8 days of culture. Immunohistochemical double labelling experiments with 3beta-HSD and BrdU antibodies showed that this increase was the result of differentiation of stem Leydig cells/precursor cells and not caused by proliferation of progenitor cells themselves. The addition of LH to the cultures consistently resulted in an increase in progenitor formation throughout the culture period. Surprisingly, when OSM and LH were added together, the LH induced rise in progenitor cells was significantly inhibited after 3 and 8 days of culture.

CONCLUSION

Taken together, the results of the present study suggest that locally produced OSM may not only play a role in the regulation of Sertoli cell proliferation and the initiation of spermatogenesis but may also play a role in the regulation of Leydig cell progenitor formation by keeping the augmenting effects of LH on this process in abeyance.

Sensitization of osteosarcoma cells to apoptosis by oncostatin M depends on STAT5 and p53

Oncostatin M (OSM), a cytokine of the interleukin-6 family, induces growth arrest and differentiation of osteoblastic cells into glial-like/osteocytic cells. Here, we asked whether OSM regulates apoptosis of normal or transformed (osteosarcoma) osteoblasts. We show that OSM sensitizes cells to apoptosis induced by various death inducers such as staurosporine, ultraviolet or tumor necrosis factor-alpha. Apoptosis is mediated by the mitochondrial pathway, with release of cytochrome c from the mitochondria to the cytosol and activation of caspases-9 and -3. DNA micro-arrays revealed that OSM modulates the expression of Bax, Bad, Bnip3, Bcl-2 and Mcl-1. Pharmacological inhibitors, dominant-negative signal transducer and activator of transcriptions (STATs), stable RNA interference and knockout cells indicated that the transcription factors p53 and STAT5, which are activated by OSM, are implicated in the sensitization to apoptosis, being responsible for Bax induction and Bcl-2 reduction, respectively. These results indicate that, in addition to growth arrest and induced differentiation, OSM also sensitizes normal and transformed osteoblasts to apoptosis by a mechanism implicating (i) activation and nuclear translocation of STAT5 and p53 and (ii) an increased Bax/Bcl-2 ratio. Therefore, association of OSM with kinase inhibitors such as Sts represents new therapeutic opportunities for wild-type p53 osteosarcoma.

Constitutive Suppressor of Cytokine Signaling 3 Expression Confers a Growth Advantage to a Human Melanoma Cell Line

The growth of melanocytes and many early stage melanoma cells can be inhibited by cytokines, whereas late stage melanoma cells have often been reported to be "multi-cytokine-resistant." Here, we analyzed the melanoma cell line 1286, resistant towards the growth-inhibitory effects of interleukin 6 (IL-6), and oncostatin M (OSM), to better understand the mechanisms underlying cytokine resistance. Although the relevant receptors gp130 and OSMR are expressed at the cell surface of these cells, cytokine stimulation hardly led to the activation of Janus kinase 1 and signal transducer and activator of transcription (STAT)3 and STAT1. We found a high-level constitutive expression of suppressors of cytokine signaling 3 (SOCS3) that did not further increase after cytokine treatment. Importantly, upon suppression of SOCS3 by short interfering RNA, cells became susceptible towards OSM and IL-6: they showed an enhanced STAT3 phosphorylation and a dramatically increased STAT1 phosphorylation. Moreover, suppression of SOCS3 rendered 1286 cells sensitive to the antiproliferative action of IL-6 and OSM, but not of IFN-alpha. Interestingly, SOCS3-short interfering RNA treatment also increased the growth-inhibitory effect in cytokine-sensitive WM239 cells expressing SOCS3 in an inducible way. Thus, SOCS3 expression confers a growth advantage to these cell lines. Constitutive SOCS3 mRNA expression, although at lower levels than in 1286 cells, was found in nine additional human melanoma cell lines and in normal human melanocytes, although at the protein level, SOCS3 expression was marginal at best. However, in situ analysis of human melanoma specimens revealed SOCS3 immunoreactivity in 3 out of 10 samples, suggesting that in vivo SOCS3 may possibly play a role in IL-6 resistance in at least a fraction of tumors.

Oncostatin M Secreted by Skin Infiltrating T Lymphocytes Is a Potent Keratinocyte Activator Involved in Skin Inflammation

Cutaneous inflammatory diseases such as psoriasis vulgaris and atopic dermatitis are associated with altered keratinocyte function, as well as with a particular cytokine production profile of skin-infiltrating T lymphocytes. In this study we show that normal human epidermal keratinocytes express a functional type II oncostatin-M (OSM) receptor (OSMR) consisting of the gp130 and OSMRbeta components, but not the type I OSMR. The type II OSMR is expressed in skin lesions from both psoriatic patients and those with atopic dermatitis. Its ligand, OSM, induces via the recruitment of the STAT3 and MAP kinase pathways a gene expression profile in primary keratinocytes and in a reconstituted epidermis that is characteristic of proinflammatory and innate immune responses. Moreover, OSM is a potent stimulator of keratinocyte migration in vitro and increases the thickness of a reconstituted epidermis. OSM transcripts are enhanced in both psoriatic and atopic dermatitic skin as compared with healthy skin and mirror the enhanced production of OSM by T cells isolated from diseased lesions. Results from a microarray analysis comparing the gene-modulating effects of OSM with those of 33 different cytokines indicate that OSM is a potent keratinocyte activator similar to TNF-alpha, IL-1, IL-17, and IL-22 and that it acts in synergy with the latter cytokines in the induction of S100A7 and beta-defensin 2 expression, characteristic of psoriatic skin. Taken together, these results demonstrate that OSM and its receptor play an important role in cutaneous inflammatory responses in general and that the specific effects of OSM are associated with distinct inflammatory diseases depending on the cytokine environment.

Oncostatin M (OSM) cytostasis of breast tumor cells: characterization of an OSM receptor beta-specific kernel

The interleukin-6 cytokine oncostatin M (OSM) induces potent growth-inhibitory and morphogenic responses in several different tumor cell types, highlighting the importance of OSM signaling mechanisms as targets for therapeutic intervention. The specific molecular pathways involved are not well understood, as OSM can signal through two separate heterodimeric receptor complexes, glycoprotein 130 (gp130)/leukemia inhibitory factor receptor (LIFR) alpha and gp130/OSM receptor beta (OSMRbeta). In this investigation, we used a LIFR antagonist to help resolve signaling responses and identify patterns of gene expression elicited by the different receptor complexes. OSM-induced biological effects on breast tumor-derived cell lines were specifically mediated through the gp130/OSMRbeta complex. Each cytokine tested exhibited differential signaling capability and manifested both shared and unique patterns of gene activation, emphasizing compositional differences in activator protein-1 transcription factor activity and expression. In particular, OSM strongly activated the c-Jun NH(2)-terminal kinase (JNK) serine/threonine kinase and downstream components, including activating transcription factor (ATF)/cyclic AMP-responsive element binding protein family member, ATF3. JNK/stress-activated protein kinase kinase inhibition abrogated cell morphogenesis induced by OSM, indicating an important role for this pathway in OSM specificity. These findings identify a core signaling/transcriptional mechanism specific to the OSMRbeta in breast tumor cells.

Regulation of pre-B cell colony-enhancing factor by STAT-3-dependent interleukin-6 trans-signaling: implications in the pathogenesis of rheumatoid arthritis

OBJECTIVE

To determine whether interleukin-6 (IL-6) trans-signaling directs the expression of pre-B cell colony-enhancing factor (PBEF) in vitro and in vivo.

METHODS

Complementary DNA from rheumatoid arthritis (RA) synovial fibroblasts treated with IL-6 and soluble IL-6 receptor (sIL-6R) was used to probe a cytokine microarray. PBEF regulation by the IL-6-related cytokines, IL-6, sIL-6R, oncostatin M (OSM), IL-11, and leukemia inhibitory factor (LIF) was determined by reverse transcription-polymerase chain reaction analysis. IL-6-mediated STAT-3 regulation of PBEF was determined using a cell-permeable STAT-3 inhibitor peptide. Antigen-induced arthritis (AIA) was induced in wild-type (IL-6(+/+)) and IL-6-deficient (IL-6(-/-)) mice. PBEF and STAT were detected by immunohistochemistry, immunoblotting, and electrophoretic mobility shift assay. Synovial levels of PBEF were quantified by enzyme immunoassay.

RESULTS

IL-6 trans-signaling regulated PBEF in a STAT-3-dependent manner. In addition, PBEF was regulated by the IL-6-related cytokine OSM, but not IL-11 or LIF. Flow cytometric analysis of the IL-6-related cognate receptors suggested that OSM regulates PBEF via its OSM receptor beta and not its LIF receptor. The involvement of PBEF in arthritis progression was confirmed in vivo, where induction of AIA resulted in a 4-fold increase in the synovial expression of PBEF. In contrast, little or no change was observed in IL-6(-/-) mice, in which the inflammatory infiltrate was markedly reduced and synovial STAT-1/3 activity was also impaired. Analysis of human RA synovial tissue confirmed that PBEF immunolocalized in apical synovial membrane cells, endothelial cells, adipocytes, and lymphoid aggregates. Synovial fluid levels of PBEF were significantly higher in RA patients than in osteoarthritis patients.

CONCLUSION

Experiments presented herein demonstrate that PBEF is regulated via IL-6 trans-signaling and the IL-6-related cytokine OSM. PBEF is also actively expressed during arthritis. Although these data confirm an involvement of PBEF in disease progression, the consequence of its action remains to be determined.

A characteristic subset of psoriasis-associated genes is induced by oncostatin-M in reconstituted epidermis

The pathological manifestations of psoriasis are orchestrated by many secreted proteins, but only a handful, tumor necrosis factor-alpha, IFN-gamma and IL-1, have been studied in great detail. Oncostatin-M (OsM) has also been found in psoriatic skin and we hypothesized that it makes a unique and characteristic contribution to the psoriatic processes. To define in-depth the molecular effects of OsM in epidermis, we used high-density DNA microarrays for transcriptional profiling of OsM-treated human skin equivalents. We identified 374 unambiguously OsM-regulated genes, out of 22,000 probed. OsM suppressed the expression of the "classical" epidermal differentiation markers, but strongly and specifically induced the S100A proteins. Cytoskeletal and complement proteins, proteases, and their inhibitors were also induced by OsM. Interestingly, a large set of genes was induced by OsM at early time points but suppressed later; these genes are known regulatory targets of IFN and thus provide a nexus between the OsM and IFN pathways. OsM induces IL-4 and suppresses the T-helper 1-type and IL-1-responsive signals, potentially attenuating the psoriatic pathology. The data suggest that OsM plays a unique role in psoriasis, different from all other, more thoroughly studied cytokines.

Forced dimerization of gp130 leads to constitutive STAT3 activation, cytokine-independent growth, and blockade of differentiation of embryonic stem cells

The mode of activation of glycoprotein 130 kDa (gp130) and the transmission of the activation status through the plasma membrane are incompletely understood. In particular, the molecular function of the three juxtamembrane fibronectin III-like domains of gp130 in signal transmission remains unclear. To ask whether forced dimerization of gp130 is sufficient for receptor activation, we replaced the entire extracellular portion of gp130 with the c-jun leucine zipper region in the chimeric receptor protein L-gp130. On expression in cells, L-gp130 stimulates ligand-independent signal transducer and activator of transcription (STAT) 3 and extracellular signal-regulated kinase 1/2 phosphorylation. gp130 activation could be abrogated by the addition of a competing peptide comprising the leucine zipper region of c-fos. When stably expressed in the interleukin-3-dependent Ba/F3 murine pre-B-cells, these cells showed constitutive STAT3 activation and cytokine-independent growth over several months. Because gp130 stimulation completely suppressed differentiation of murine embryonic stem cells in vitro, we also stably expressed L-gp130 in these cells, which completely blocked their differentiation in the absence of cytokine stimulation and was consistent with high constitutive expression levels of the stem cell factor OCT-4. Thus, L-gp130 can be used in vitro and in vivo to mimic constitutive and ligand-independent activation of gp130 and STAT3, the latter of which is frequently observed in neoplastic diseases.

Oncostatin-M Up-Regulates VCAM-1 and Synergizes with IL-4 in Eotaxin Expression: Involvement of STAT6

Oncostatin-M (OSM) is an IL-6/gp130 family member that can stimulate the eosinophil-selective CC chemokine eotaxin-1 in vitro and eosinophil accumulation in mouse lung in vivo. The adhesion molecule VCAM-1 and eotaxin have been implicated in extravasation and accumulation of eosinophils into tissue in animal models of asthma. In this study, we investigated the role of OSM in regulation of VCAM-1 expression, and STAT6 tyrosine 641 phosphorylation in murine fibroblasts. OSM induced VCAM-1 expression in C57BL/6 mouse lung fibroblasts (MLF) and NIH 3T3 fibroblasts at the protein and mRNA level in vitro. OSM also induced STAT6 Y641 phosphorylation in MLF and NIH 3T3 fibroblasts, an activity not observed with other IL-6/gp130 cytokine family members (IL-6, leukemia inhibitory factor, cardiotropin-1, and IL-11) nor in cells derived from STAT6(-/-) mice (STAT6(-/-) MLF). STAT6 was not essential for OSM-induced VCAM-1 or eotaxin-1 as assessed in STAT6(-/-) MLF. Combination of IL-4 and OSM synergistically enhanced eotaxin-1 expression in MLF. IL-4 induction and the IL-4/OSM synergistic induction of eotaxin-1 was abrogated in STAT6(-/-) MLF, however, regulation of IL-6 was similar in -/- or wild-type MLF. Induction of VCAM-1 by OSM was diminished by pharmacological inhibitors of PI3K (LY294002) but not inhibitors of ERK1/2 (PD98059) or p38 MAPK (SB203580). These data support the role of OSM in eosinophil accumulation into lung tissue through eotaxin-1 and VCAM-1 expression and the notion that OSM is able to induce unique signal transduction events through its receptor complex of OSMR beta-chain and gp130.

Breast cancer cells stimulate neutrophils to produce oncostatin M: potential implications for tumor progression

Tumor-associated and tumor-infiltrating neutrophils (TAN) and macrophages (TAM) can account for as much as 50% of the total tumor mass in invasive breast carcinomas. It is thought that tumors secrete factors that elicit a wound-repair response from TAMs and TANs and that this response inadvertently stimulates tumor progression. Oncostatin M is a pleiotropic cytokine belonging to the interleukin-6 family that is expressed by several cell types including activated human T lymphocytes, macrophages, and neutrophils. Whereas oncostatin M can inhibit the proliferation of breast cancer cells in vitro, recent studies suggest that oncostatin M may promote tumor progression by enhancing angiogenesis and metastasis. In addition, neutrophils can be stimulated to synthesize and rapidly release large quantities of oncostatin M. In this article, we show that human neutrophils secrete oncostatin M when cocultured with MDA-MB-231 and T47D human breast cancer cells. Neutrophils isolated from whole blood or breast cancer cells alone express little oncostatin M by immunocytochemistry and ELISA, but neutrophils express and release high levels of oncostatin M when they are cocultured with breast cancer cells. In addition, we show that granulocyte-macrophage colony-stimulating factor produced by breast cancer cells and cell-cell contact are both necessary for the release of oncostatin M from neutrophils. Importantly, neutrophil-derived oncostatin M induces vascular endothelial growth factor from breast cancer cells in coculture and increases breast cancer cell detachment and invasive capacity, suggesting that neutrophils and oncostatin M may promote tumor progression in vivo.

Transcriptional responses of human epidermal keratinocytes to Oncostatin-M

Oncostatin-M (OsM) plays an important role in inflammatory and oncogenic processes in skin, including psoriasis and Kaposi sarcoma. However, the molecular responses to OsM in keratinocytes have not been explored in depth. Here we show the results of transcriptional profiling in OsM-treated primary human epidermal keratinocytes, using high-density DNA microarrays. We find that OsM strongly and specifically affects the expression of many genes, in particular those involved with innate immunity, angiogenesis, adhesion, motility, tissue remodeling, cell cycle and transcription. The timing of the responses to OsM comprises two waves, early at 1h, and late at 48 h, with much fewer genes regulated in the intervening time points. Secreted cytokines and growth factors and their receptors, as well as nuclear transcription factors, are primary targets of OsM regulation, and these, in turn, effect the secondary changes.

Dynamics of the gp130 cytokine complex: a model for assembly on the cellular membrane

Cytokines of the interleukin-6 (IL-6)-type family all bind to the glycoprotein gp130 on the cell surface and require interaction with two gp130 or one gp130 and another related signal transducing receptor subunit. In addition, some cytokines of this family, such as IL-6, interleukin-11, ciliary neurotrophic factor, neuropoietin, cardiotrophin-1, and cardiotrophin-1-like-cytokine, interact with specific ligand binding receptor proteins. High- and low-affinity binding sites have been determined for these cytokines. So far, however, the stoichiometry of the signaling receptor complexes has remained unclear, because the formation of the cytokine/cytokine-receptor complexes has been analyzed with soluble receptor components in solution, which do not necessarily reflect the situation on the cellular membrane. Consequently, the binding affinities measured in solution have been orders of magnitude below the values obtained with whole cells. We have expressed two gp130 extracellular domains in the context of a Fc-fusion protein, which fixes the receptors within one dimension and thereby restricts the flexibility of the proteins in a fashion similar to that within the plasma membrane. We measured binding of IL-6 and interleukin-b receptor (IL-6R) by means of fluorescence-correlation spectroscopy. For the first time we have succeeded in recapitulating in a cell-free condition the binding affinities and dynamics of IL-6 and IL-6R to the gp130 receptor proteins, which have been determined on whole cells. Our results demonstrate that a dimer of gp130 first binds one IL-6/IL-6R complex and only at higher ligand concentrations does it bind a second IL-6/IL-6R complex. This view contrasts with the current perception of IL-6 receptor activation and reveals an alternative receptor activation mechanism.