Interactions between oncostatin M and the IL-6 signal transducer, gp130

Coordination of Immune-Stroma Crosstalk by IL-6 Family Cytokines

Stromal cells are a subject of rapidly growing immunological interest based on their ability to influence virtually all aspects of innate and adaptive immunity. Present in every bodily tissue, stromal cells complement the functions of classical immune cells by sensing pathogens and tissue damage, coordinating leukocyte recruitment and function, and promoting immune response resolution and tissue repair. These diverse roles come with a price: like classical immune cells, inappropriate stromal cell behavior can lead to various forms of pathology, including inflammatory disease, tissue fibrosis, and cancer. An important immunological function of stromal cells is to act as information relays, responding to leukocyte-derived signals and instructing leukocyte behavior in kind. In this regard, several members of the interleukin-6 (IL-6) cytokine family, including IL-6, IL-11, oncostatin M (OSM), and leukemia inhibitory factor (LIF), have gained recognition as factors that mediate crosstalk between stromal and immune cells, with diverse roles in numerous inflammatory and homeostatic processes. This review summarizes our current understanding of how IL-6 family cytokines control stromal-immune crosstalk in health and disease, and how these interactions can be leveraged for clinical benefit.

IL-6 and ovarian cancer: inflammatory cytokines in promotion of metastasis

Ovarian cancer is the most fatal gynecological cancer in the USA and the fifth most common cancer-related cause of death in women. Inflammation has been shown to play many roles in ovarian cancer tumor growth, with the proinflammatory cytokine interleukin-6 (IL-6) having been established as a key immunoregulatory cytokine. Ovarian cancer cells continuously secrete cytokines that promote tumorigenicity in both autocrine and paracrine fashions while also receiving signals from the tumor microenvironment (TME). The TME contains many cells including leukocytes and fibroblasts, which respond to proinflammatory cytokines and secrete their own cytokines, which can produce many effects including promotion of chemoresistance, resistance to apoptosis, invasion, angiogenesis by way of overexpression of vascular endothelial growth factor, and promotion of metastatic growth at distant sites. IL-6 and its proinflammatory family members, including oncostatin M, have been found to directly stimulate enhanced invasion of cancer cells through basement membrane degradation caused by the overexpression of matrix metalloproteinases, stimulate promotion of cell cycle, enhance resistance to chemotherapy, and cause epithelial-to-mesenchymal transition (EMT). IL-6 has been shown to activate signaling pathways that lead to tumor proliferation, the most studied of which being the Janus kinase (JAK) and STAT3 pathway. IL-6-induced JAK/STAT activation leads to constitutive activation of STAT3, which has been correlated with enhanced tumor cell growth and resistance to chemotherapy. IL-6 has also been shown to act as a trigger of the EMT, the hypothesized first step in the metastatic cascade. Understanding the important role of IL-6 and its family members' effects on the pathogenesis of ovarian cancer tumor growth and metastasis may lead to more novel treatments, detection methods, and improvement of overall clinical outcomes.

Neuropathies of Stüve-Wiedemann Syndrome due to mutations in leukemia inhibitory factor receptor (LIFR) gene

Stüve-Wiedemann syndrome (STWS; OMIM #610559) is a rare disease that results in dysfunction of the autonomic nervous system, which controls involuntary processes such as breathing rate and body temperature. In infants, this can result in respiratory distress, feeding and swallowing difficulties, and hyperthermic episodes. Individuals may sweat excessively when body temperature is not elevated. Additionally, individuals have reduced ability to feel pain and may lose reflexes such as the corneal reflex that normally causes one to blink, and the patellar reflex resulting in the knee-jerk. STWS usually results in infant mortality, yet some STWS patients survive into early adulthood. STWS is caused by a mutation in the leukemia inhibitory factor receptor (LIFR) gene, which is inherited in an autosomal-recessive pattern. Most LIFR mutations resulting in STWS cause instability of the mRNA due to frameshift mutations leading to premature stop codons, which prevent the formation of LIFR protein. STWS is managed on a symptomatic basis as no treatment is currently available.

Stüve-Wiedemann syndrome: LIFR and associated cytokines in clinical course and etiology

Stüve-Wiedemann syndrome (STWS; OMIM #610559) is a rare bent-bone dysplasia that includes radiologic bone anomalies, respiratory distress, feeding difficulties, and hyperthermic episodes. STWS usually results in infant mortality, yet some STWS patients survive into and, in some cases, beyond adolescence. STWS is caused by a mutation in the leukemia inhibitory factor receptor (LIFR) gene, which is inherited in an autosomally recessive pattern. Most LIFR mutations resulting in STWS are null mutations which cause instability of the mRNA and prevent the formation of LIFR, impairing the signaling pathway. LIFR signaling usually follows the JAK/STAT3 pathway, and is initiated by several interleukin-6-type cytokines. STWS is managed on a symptomatic basis since there is no treatment currently available.

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.

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.

Murine oncostatin M stimulates mouse synovial fibroblasts in vitro and induces inflammation and destruction in mouse joints in vivo

Oncostatin M (OSM) is a multifunctional cytokine, a member of the interleukin-6/leukemia inhibitory factor (IL-6/LIF) family, that can regulate a number of connective-tissue cell types in vitro including cartilage and synovial tissue-derived fibroblasts, however its role in joint inflammation in vivo is not clear. We have analyzed murine OSM (muOSM) activity in vitro and in vivo in mouse joint tissue, to determine the potential role of this cytokine in local joint inflammation and pathology. The effects of muOSM and other IL-6/LIF cytokines on mouse synovial fibroblast cultures were assessed in vitro and showed induction of monocyte chemotactic protein-1, interleukin-6, and tissue inhibitor metalloproteinase-1, as well as enhancement of colony growth in soft agarose culture. Other IL-6/LIF cytokines including IL-6, LIF, or cardiotrophin-1, did not have such effects when tested at relatively high concentrations (20 ng/ml). To assess effects of muOSM in articular joints in vivo, we used recombinant adenovirus expressing muOSM cDNA (AdmuOSM) and injected purified recombinant virus (10(6) to 10(8) pfu) intra-articularly into the knees of various mouse strains. Histological analysis revealed dramatic alterations in the synovium but not in synovium of knees treated with the control virus Ad-dl70 or knees treated with Adm-IL-6 encoding biologically active murine IL-6. AdmuOSM effects were characterized by increases in the synovial cell proliferation, infiltration of mononuclear cells, and increases in extracellular matrix deposition that were evident at day 4, but much more marked at days 7, 14, and 21 after administration. The synovium took on characteristics similar to pannus and appeared to contact and invade cartilage. Collectively, these results provide good evidence that OSM regulates synovial fibroblast function differently than other IL-6-type cytokines, and can induce a proliferative invasive phenotype of synovium in vivo in mice on overexpression. We suggest that OSM may contribute to pathology in arthritis.

Oncostatin M is produced during pregnancy by decidual cells and stimulates the release of HCG

Oncostatin M (OSM) is a member of the interleukin-6 superfamily and a multifunctional cytokine that effects the growth and differentiation of many different cell types. OSM concentrations in the sera of pregnant women were found to be significantly higher than those of non-pregnant women. Western blot analysis revealed that the OSM protein was present in the decidua and chorionic tissue in each trimester. Throughout pregnancy, the amount of the OSM protein in the decidua was larger than that in the chorionic tissue. Immunohistochemistry using an anti-OSM monoclonal antibody demonstrated that OSM was mainly localized in the decidual glands and stroma. OSM transcripts in the decidua and the chorionic tissue were detected during each trimester by reverse transcription-polymerase chain reaction (RT-PCR). The regulation of human chorionic gonadotrophin (HCG) release by the placenta in first trimester stimulated with recombinant OSM was also investigated. Stimulation of the placenta by OSM augmented HCG release in a time- and dose-dependent manner. HCG release induced by recombinant human OSM was completely blocked by antibodies against OSM and the signal transducer, gp130, but only partially inhibited by antibodies against the leukaemia inhibiting factor (LIF) receptor. These results suggest that OSM molecules produced by decidual glands and stromal cells during pregnancy have an important role in placental endocrine function.

Oncostatin M: development of a pleiotropic cytokine

Oncostatin M (OM) is a member of the interleukin-6 (IL-6) cytokine subfamily. The binding of OM to its receptor initiates signal transduction through JAK-signal transducers and activators of transcription (STAT) pathways and activates transcription activators through mitogen-activated protein (MAP) kinases. Results of in vitro assays documented that OM modulates cytokine expression and alters the production of proteases that down-regulate inflammation. Administration of OM to lipopolysaccharide (LPS)-challenged mice lowered serum tumor necrosis factor-alpha (TNF-alpha) levels and decreased the lethal effects of LPS administration. OM also reduced inflammation in animal models of human disease, including inflammatory bowel disease, antibody-induced arthritis, and experimental autoimmune encephalomyelitis. Preclinical safety studies have been conducted in the mouse and monkey. Mice were administered OM (subcutaneously) at 72, 360, or 1,560 micrograms/kg/day in a 2-wk toxicity study. Decreased body weights occurred at 1,560 micrograms/kg. Drug-related changes at 360 and 1,560 micrograms/kg consisted of dermal irritation at the injection site, leukopenia, and thymic lymphoid depletion; all changes were reversible following a 2-wk recovery period. In a 2-wk subcutaneous study in monkeys, OM was administered at 1, 5, 15, 45, or 150 micrograms/kg/day. At all doses there was reversible, transient inappetence and dermal irritation at the injection site. Drug-related changes at 5, 15, 45, and 150 micrograms/kg consisted of reversible elevations in both serum amyloid A and IL-6, and reversible thymic lymphoid depletion. Transient increases in body temperature occurred at 15, 45, and 150 micrograms/kg. The observed spectrum of immunomodulatory effects suggests that OM may have therapeutic utility in treating chronic inflammatory diseases.

Leukemia inhibitory factor: part of a large ingathering family

Leukemia Inhibitory Factor (LIF) has a wide variety of biological activities. It regulates the differentiation of embryonic stem cells, neural cells, osteoblasts, adipocytes, hepatocytes and kidney epithelial cells. It also triggers the proliferation of myoblasts, primordial germ cells and some endothelial cells. Many of these biological functions parallel those of interleukin-6, Oncostatin M, ciliary neurotrophic factor, interleukin-11 and cardiotrophin-1. These structurally related cytokines also share subunits of their receptors which could partially explain the redundancy in this system of soluble mediators. In vivo LIF proves important in regulating the inflammatory response by fine tuning of the delicate balance of at least four systems in the body, namely the immune, the hematopoietic, the nervous and the endocrine systems. Although we are far from its therapeutic applications, the fast increasing knowledge in this field may bring new insights for the understanding of the cytokine biology in general.

Evidence for the formation of a heterotrimeric complex of leukaemia inhibitory factor with its receptor subunits in solution

Leukaemia inhibitory factor (LIF) is a polyfunctional cytokine that is known to require at least two distinct receptor components (LIF receptor alpha-chain and gp130) in order to form a high-affinity, functional, receptor complex. Human LIF binds with unusually high affinity to a naturally occurring mouse soluble LIF receptor alpha-chain, and this property was used to purify a stable complex of human LIF and mouse LIF receptor alpha-chain from pregnant-mouse serum. Recombinant soluble human gp130 was expressed, with a FLAG(R) epitope (DYKDDDDK) at the N-terminus, in the methylotropic yeast Pichia pastoris and purified using affinity chromatography. The formation of a trimeric complex in solution was established by native gel electrophoresis, gel-filtration chromatography, sedimentation equilibrium analysis, surface plasmon resonance spectroscopy and chemical cross-linking. The stoichiometry of this solution complex was 1:1:1, in contrast with that of the complex of interleukin-6, the interleukin-6-specific low-affinity receptor subunit and gp130, which is 2:2:2.

Kaposi's sarcoma: advances and perspectives

Kaposi's sarcoma (KS) is an unusual neoplasm that has proved to be an enigma in many ways since its original description by Kaposi in 1872. Its epidemiology has stimulated tremendous interest, amplified markedly in 1981 when it became known as an original defining part of the complex of immune disorders now known as AIDS. The cell of origin, etiology, and therapy for both AIDS-associated and AIDS-unassociated KS continue as matters of intense investigation. In fact, whether it is a reactive hyperplasia or a true malignancy is still a matter of debate, as is the concept of multicentricity versus metastases. Epidemiologic studies suggest that a separate agent apart from HIV-1 may cause KS. A newly postulated KS-associated herpes virus may be linked. The role of the HIV-1 tat gene product, basic fibroblast growth factor, scatter factor, oncostatin M, and other factors that regulate the growth of KS cells are discussed, as well as therapeutic options.

AIDS-associated Kaposi's sarcoma (KS) cells express oncostatin M (OM)-specific receptor but not leukemia inhibitory factor/OM receptor or interleukin-6 receptor. Complete block of OM-induced KS cell growth and OM binding by anti-gp130 antibodies

Oncostatin M (OM), which shares functional similarity and structural homology to leukemia inhibitory factor (LIF) and interleukin-6 (IL-6), functions as a potent growth factor for AIDS-associated Kaposi's sarcoma-derived cells (AIDS-KS cells). OM was also suggested to bind to the LIF receptor (LIF/OM receptor), which consists of a signal transducing subunit for LIF and IL-6 (gp130) and a LIF receptor alpha-subunit. Recent studies indicate that IL-6 has growth-stimulating activity for AIDS-KS cells. However, we find that AIDS-KS cell growth is exclusively induced by OM and not by LIF or IL-6. We also observed the lack of binding properties of AIDS-KS cells for LIF and IL-6. Scatchard plots revealed the existence of two affinity classes of OM receptor sites on AIDS-KS cells, with Kd values of 6-12 pM (high affinity) and 521-815 pM (low affinity). In competition binding studies, we find that the OM-specific receptor, but not the LIF/OM receptor, contributes to the OM-specific growth stimulation of AIDS-KS cells. We also noted that anti-gp130 antibodies can completely abolish OM-induced growth stimulation of AIDS-KS cells as well as OM binding to AIDS-KS cells. PCR amplification clearly revealed high levels of gp130 expression in AIDS-KS cells, while the transcript of LIF receptor alpha-subunit or IL-6 receptor alpha-subunit was not observed. Therefore, we conclude that (a) AIDS-KS cells express the OM-specific receptor with high and low affinity, but not the LIF/OM receptor; (b) gp130 on AIDS-KS cells plays a key role in OM binding and signaling on the OM-specific receptor; and (c) the lack of biological response of AIDS-KS cells to IL-6 and LIF can be explained by the absence of the IL-6 and LIF/OM receptors. All this evidence shows the correlation of OM-specific biological activity with expression of the OM-specific receptor and the involvement of gp130 on this receptor, as based on findings in in vitro growth assays and binding experiments for AIDS-KS cells.

The membrane distal half of gp130 is responsible for the formation of a ternary complex with IL-6 and the IL-6 receptor

Gp130 is the signal transducing subunit of the interleukin-6 receptor. Signaling is initiated by the complex formation of gp130 with IL-6 bound to the IL-6 receptor (IL-6R). We have subdivided the extracellular domain of gp130 in two parts and expressed the mutant proteins as soluble IgG fusion proteins in COS-7 cells. By studying the formation of the ternary complex we show that the membrane distal half of gp130 which contains a cytokine receptor domain is responsible for the interaction with the IL-6/IL-6R complex. Interestingly this is the same region which is believed to be involved in specific recognition of the related cytokines LIF, OM, and probably also of CNTF and IL-11.

LIF and OM directly interact with a soluble form of gp130, the IL-6 receptor signal transducing subunit

Oncostatin M and LIF are related members of a cytokine family that also includes IL-6, CNTF and G-CSF. These proteins exhibit overlapping biological properties and with the exception of G-CSF, they all appear to utilize gp130 as a signaling component of their high affinity receptor complexes. Recently it has been demonstrated that monomeric, membrane bound gp130 can directly bind OM. To further investigate the binding properties of gp130 we generated a soluble form of gp130, sgp130-Rg, to investigate potential gp130 interactions with OM and other members of this cytokine family. Using chemical crosslinking techniques we demonstrate that OM and LIF but not CNTF or IL-6 directly interact with sgp130-Rg. Since OM signaling can be prevented by binding gp130 with anti gp130 mAbs we also investigated the potential of sgp130-Rg to prevent the biological activities of both LIF and OM. Here we demonstrate that sgp130-Rg can bind LIF and OM preventing their biological activities on the TF-1 erythroleukemia cell line. This property suggests that sgp130-Rg may have therapeutic value in the specific prevention of LIF or OM mediated pathologies.