Oncostatin-M stimulates tyrosine protein phosphorylation in parallel with the activation of p42MAPK/ERK-2 in Kaposi's cells. Evidence that this pathway is important in Kaposi cell growth

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.

HIV-Associated Cancer Biomarkers: A Requirement for Early Diagnosis

Globally, HIV/AIDS and cancer are increasingly public health problems and continue to exist as comorbidities. The sub-Saharan African region has the largest number of HIV infections. Malignancies previously associated with HIV/AIDS, also known as the AIDS-defining cancers (ADCs) have been documented to decrease, while the non-AIDS defining cancer (NADCs) are on the rise. On the other hand, cancer is a highly heterogeneous disease and precision oncology as the most effective cancer therapy is gaining attraction. Among HIV-infected individuals, the increased risk for developing cancer is due to the immune system of the patient being suppressed, frequent coinfection with oncogenic viruses and an increase in risky behavior such as poor lifestyle. The core of personalised medicine for cancer depends on the discovery and the development of biomarkers. Biomarkers are specific and highly sensitive markers that reveal information that aid in leading to the diagnosis, prognosis and therapy of the disease. This review focuses mainly on the risk assessment, diagnostic, prognostic and therapeutic role of various cancer biomarkers in HIV-positive patients. A careful selection of sensitive and specific HIV-associated cancer biomarkers is required to identify patients at most risk of tumour development, thus improving the diagnosis and prognosis of the disease.

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.

Classic and Novel Adipocytokines at the Intersection of Obesity and Cancer: Diagnostic and Therapeutic Strategies

PURPOSE OF REVIEW

In this review, we investigate the role of classic and novel adipocytokines in cancer pathogenesis synopsizing the mechanisms underlying the association between adipocytokines and malignancy. Special emphasis is given on novel adipocytokines as new evidence is emerging regarding their entanglement in neoplastic development.

RECENT FINDINGS

Recent data have emphasized the role of the triad of overweight/obesity, insulin resistance and adipocytokines in cancer. In the setting of obesity, classic and novel adipocytokines present independent and joint effects on activation of major intracellular signaling pathways implicated in cell proliferation, expansion, survival, adhesion, invasion, and metastasis. Until now, more than 15 adipocytokines have been associated with cancer, and this list continues to expand. While the plethora of circulating pro-inflammatory adipocytokines, such as leptin, resistin, extracellular nicotinamide phosphoribosyl transferase, and chemerin are elevated in malignancies, some adipocytokines such as adiponectin and omentin-1 are generally decreased in cancers and are considered protective against carcinogenesis. Elucidating the intertwining of inflammation, cellular bioenergetics, and adiposopathy is significant for the development of preventive, diagnostic, and therapeutic strategies against cancer. Novel more effective and safe adipocytokine-centered therapeutic interventions may pave the way for targeted oncotherapy.

Role of Pattern Recognition Receptors in KSHV Infection

Kaposi’s sarcoma-associated herpesvirus or Human herpesvirus-8 (KSHV/HHV-8), an oncogenic human herpesvirus and the leading cause of cancer in HIV-infected individuals, is a major public health concern with recurring reports of epidemics on a global level. The early detection of KSHV virus and subsequent activation of the antiviral immune response by the host’s immune system are crucial to prevent KSHV infection. The host’s immune system is an evolutionary conserved system that provides the most important line of defense against invading microbial pathogens, including viruses. Viruses are initially detected by the cells of the host innate immune system, which evoke concerted antiviral responses via the secretion of interferons (IFNs) and inflammatory cytokines/chemokines for elimination of the invaders. Type I IFN and cytokine gene expression are regulated by multiple intracellular signaling pathways that are activated by germline-encoded host sensors, i.e., pattern recognition receptors (PRRs) that recognize a conserved set of ligands, known as ‘pathogen-associated molecular patterns (PAMPs)’. On the contrary, persistent and dysregulated signaling of PRRs promotes numerous tumor-causing inflammatory events in various human cancers. Being an integral component of the mammalian innate immune response and due to their constitutive activation in tumor cells, targeting PRRs appears to be an effective strategy for tumor prevention and/or treatment. Cellular PRRs are known to respond to KSHV infection, and KSHV has been shown to be armed with an array of strategies to selectively inhibit cellular PRR-based immune sensing to its benefit. In particular, KSHV has acquired specific immunomodulatory genes to effectively subvert PRR responses during the early stages of primary infection, lytic reactivation and latency, for a successful establishment of a life-long persistent infection. The current review aims to comprehensively summarize the latest advances in our knowledge of role of PRRs in KSHV infections.

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 activates STAT3 to promote endometrial cancer invasion and angiogenesis

Oncostatin M (OSM), a pleiotropic cytokine, can either promote or inhibit the growth of tumors derived from specific tissues. However, little is known about the activity and expression pattern of OSM in endometrial cancers (ECs). Herein we show that expression of OSM in human ECs was significantly higher than that in hyperplastic or normal tissues. In EC tissues, high OSM levels were positively correlated with tumor stage, histological grade, myometrial invasion, and lymph node metastasis. Additionally, we demonstrated that recombinant human OSM (rhOSM) promoted tumor angiogenesis in EC cell lines by activating STAT3 (signal transducer and activator of transcription 3) and enhanced both cell migration and cell invasion. rhOSM did not, however, influence the proliferation of EC cells in vitro. In contrast, in our in vivo xenograft model, overexpression of rhOSM promoted cell proliferation, tumor growth, and angiogenesis in nude mice. Collectively, these experiments suggest that OSM may be a tumor promoter that encourages EC progression. OSM may thus serve as a potential target of antiangiogenic therapy for endometrial cancer.

Biomarkers of HIV-associated Cancer

Cancer biomarkers have provided great opportunities for improving the management of cancer patients by enhancing the efficiency of early detection, diagnosis, and efficacy of treatment. Every cell type has a unique molecular signature, referred to as biomarkers, which are identifiable characteristics such as levels or activities of a myriad of genes, proteins, or other molecular features. Biomarkers can facilitate the molecular definition of cancer, provide information about the course of cancer, and predict response to chemotherapy. They offer the hope of early detection as well as tracking disease progression and recurrence. Current progress in the characterization of molecular genetics of HIV-associated cancers may form the basis for improved patient stratification and future targeted or individualized therapies. Biomarker use for cancer staging and personalization of therapy at the time of diagnosis could improve patient care. This review focuses on the relevance of biomarkers in the most common HIV-associated malignancies, namely, Kaposi sarcoma, non-Hodgkin’s lymphoma, and invasive cervical cancer.

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.

Hemangiosarcoma in rodents: mode-of-action evaluation and human relevance

Although rarely occurring in humans, hemangiosarcomas (HS) have become important in evaluating the potential human risk of several chemicals, including industrial, agricultural, and pharmaceutical agents. Spontaneous HS arise frequently in mice, less commonly in rats, and frequently in numerous breeds of dogs. This review explores knowledge gaps and uncertainties related to the mode of action (MOA) for the induction of HS in rodents, and evaluates the potential relevance for human risk. For genotoxic chemicals (vinyl chloride and thorotrast), significant information is available concerning the MOA. In contrast, numerous chemicals produce HS in rodents by nongenotoxic, proliferative mechanisms. An overall framework is presented, including direct and indirect actions on endothelial cells, paracrine effects in local tissues, activation of bone marrow endothelial precursor cells, and tissue hypoxia. Numerous obstacles are identified in investigations into the MOA for mouse HS and the relevance of the mouse tumors to humans, including lack of identifiable precursor lesions, usually late occurrence of the tumors, and complexities of endothelial biology. This review proposes a working MOA for HS induced by nongenotoxic compounds that can guide future research in this area. Importantly, a common MOA appears to exist for the nongenotoxic induction of HS, where there appears to be a convergence of multiple initiating events (e.g., hemolysis, decreased respiration, adipocyte growth) leading to either dysregulated angiogenesis and/or erythropoiesis that results from hypoxia and macrophage activation. These later events lead to the release of angiogenic growth factors and cytokines that stimulate endothelial cell proliferation, which, if sustained, provide the milieu that can lead to HS formation.

CD13/APN transcription is regulated by the proto-oncogene c-Maf via an atypical response element

Angiogenic growth factors induce the transcription of the cell surface peptidase CD13/APN in activated endothelial cells of the tumor vasculature. Inhibition of CD13/APN abrogates endothelial invasion and morphogenesis in vitro and tumor growth in vivo suggesting a critical functional role for CD13 in angiogenesis. Experiments to identify the transcription factors responsible for this regulation demonstrated that exogenous expression of the proto-oncogene c-Maf, but not other bZip family members tested, potently activates transcription from a critical regulatory region of the CD13 proximal promoter between -115 and -70 bp which is highly conserved among mammalian species. Using promoter mutation, EMSA and ChIP analyses we established that both endogenous and recombinant c-Maf directly interact with an atypical Maf response element contained within this active promoter region via its basic DNA/leucine zipper domain. However full activity of c-Maf requires the amino-terminal transactivation domain, and site-directed mutation of putative phosphorylation sites within the transactivation domain (serines 15 and 70) shows that these sites behave in a dramatic cell type-specific manner. Therefore, this atypical response element predicts a broader range of c-Maf target genes than previously appreciated and thus impacts its regulation of multiple myeloma as well as endothelial cell function and angiogenesis.

Oncostatin M, a multifunctional cytokine

Oncostatin M (OSM) is a multifunctional cytokine that belongs to the Interleukin (IL)-6 subfamily. Among the family members, OSM is most closely related to leukemia inhibitory factor (LIF) and it in fact utilizes the LIF receptor in addition to its specific receptor in the human. While OSM was originally recognized by its unique activity to inhibit the proliferation of tumor cells, accumulating evidence now indicates that OSM exhibits many unique biological activities in inflammation, hematopoiesis, and development. Here, we review the profile of OSM activities, receptors, and signal transduction.

A G protein-coupled receptor encoded by rhesus rhadinovirus is similar to ORF74 of Kaposi's sarcoma-associated herpesvirus

Rhesus rhadinovirus (RRV) is a gamma-2 herpesvirus and is the rhesus macaque homologue of human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus. DNA sequence analysis of RRV indicates that it shares numerous open reading frames (ORFs) with HHV-8, including one (ORF74) encoding a seven-transmembrane-spanning G protein-coupled receptor (GPCR) with similarity to cellular chemokine receptors. Examination of the predicted amino acid sequence of RRV ORF74 reveals that it encodes a seven-transmembrane-spanning GPCR sharing 40.8% amino acid sequence identity with HHV-8 ORF74 and 24.1% amino acid sequence identity with rhesus macaque CXCR2. In addition, immunofluorescence studies indicate that an epitope-tagged version of RRV ORF74 is expressed on the surfaces of transfected cells, suggesting that this protein is in fact a membrane receptor. In in vitro cell culture assays, RRV ORF74 possesses transforming potential, as NIH 3T3 clones stably expressing the receptor demonstrate an increased ability to grow in soft agarose and to induce tumor formation in nude mice. Further analysis of RRV ORF74 indicates that expression of the receptor in NIH 3T3 cells causes an increased secretion of vascular endothelial growth factor and activation of the ERK1/2 (p44/42) mitogen-activated protein kinase signaling pathway. The results of these studies suggest that RRV ORF74 encodes a GPCR with properties similar to those of its homologue in HHV-8 and that this gene may play a role in RRV-associated pathogenesis.

Oncostatin M regulates eotaxin expression in fibroblasts and eosinophilic inflammation in C57BL/6 mice

Oncostatin M (OSM) is a member of the IL-6/LIF (or gp130) cytokine family, and its potential role in inflammation is supported by a number of activities identified in vitro. In this study, we investigate the action of murine OSM on expression of the CC chemokine eotaxin by fibroblasts in vitro and on mouse lung tissue in vivo. Recombinant murine OSM stimulated eotaxin protein production and mRNA levels in the NIH 3T3 fibroblast cell line. IL-6 could regulate a small induction of eotaxin in NIH 3T3 cells, but other IL-6/LIF cytokines (LIF, cardiotrophin-1 (CT-1)) had no effect. Cell signaling studies showed that murine OSM, LIF, IL-6, and CT-1 stimulated the tyrosine phosphorylation of STAT-3, suggesting STAT-3 activation is not sufficient for eotaxin induction in NIH 3T3 cells. OSM induced ERK-1,2 and p38 mitogen-activated protein kinase phosphorylation in NIH 3T3 cells, and inhibitors of ERK (PD98059) or p38 (SB203580) could partially reduce OSM-induced eotaxin production, suggesting partial dependence on mitogen-activated protein kinase signaling. OSM (but not LIF, IL-6, or CT-1) also induced eotaxin release by mouse lung fibroblast cultures derived from C57BL/6 mice. Overexpression of murine OSM in lungs of C57BL/6 mice using an adenovirus vector encoding murine OSM resulted in a vigorous inflammatory response by day 7 after intranasal administration, including marked extracellular matrix accumulation and eosinophil infiltration. Elevated levels of eotaxin mRNA in whole lung were detected at days 4 and 5. These data strongly support a role of OSM in lung inflammatory responses that involve eosinophil infiltration.

Activation of signal transducer and activator of transcription 1 (STAT1) is not sufficient for the induction of STAT1-dependent genes in endothelial cells. Comparison of interferon-gamma and oncostatin M

We compared human endothelial cell (EC) responses to interferon-gamma (IFN gamma) and oncostatin M (OnM), cytokines that utilize Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. Both cytokines cause phosphorylation of Tyr residue 701 and Ser residue 727 of STAT1, as shown by immunoblotting. Both activate DNA binding of STAT1 homodimers, shown by electrophoretic mobility shift assay. However, only IFN gamma increases expression of three STAT1-dependent gene products examined, namely transporter associated with antigen processing-1 (TAP1), interferon regulatory factor-1 (IRF1), and class I major histocompatibility complex (MHC) protein, as demonstrated by immunoblotting. Only IFN gamma increases TAP1 transcription assessed by reporter gene assay. OnM pretreatment or co-treatment does not inhibit IFN gamma responses. Interestingly, IFN gamma activation of STAT1 is considerably more long-lived than that produced by OnM. To determine whether duration is functionally significant, we transduced EC with a chimeric receptor containing extracellular domains of platelet-derived growth factor receptor beta and intracellular regions of gp130, the signaling subunit of the OnM receptor, mutated to prevent binding of the tyrosine phosphatase SHP-2. Addition of platelet-derived growth factor to such transduced cells produces STAT1 activation that is comparable in magnitude and duration to that caused by IFN gamma, but still fails to induce TAP1, IRF1, or class I MHC molecules. OnM also activates STAT1 but not transcription of STAT1-dependent genes in HepG2 cells. Transient transfection of HepG2 cells with a STAT-defective mouse IFN gamma receptor failed to complement the OnM STAT signal. We conclude that STAT1 activation is necessary but not sufficient for induction of transcription of IFN gamma-responsive genes. However, signals provided by IFN gamma other than STAT1 activation cannot be provided in trans to complement the response to OnM.

Differential response to Tat and FGF-2 of two novel clonal populations derived from murine Kaposi-like lesions developing in Tat transgenic mice

Kaposi's sarcoma (KS), a highly vascularized multifocal tumor frequent and aggressive in HIV-infected individuals, is initiated and maintained by the concomitant action of HIV-1 Tat, cytokines, and growth factors. Spindle cells, the proliferative component of KS lesions, were isolated from Kaposi-like lesions developing in Tat transgenic mice and cloned. Here we describe the behavior of two of the clones obtained: cells from clone 1 showed the classical endothelial phenotype and were therefore named murine endothelial cells (MEC), while cells from clone 2 had a typical spindle shape, coexpressed markers of endothelial, smooth muscle, and macrophage lineage; and were named spindle cells (SC). Tat stimulated MEC growth and migration, but not uPA production, suggesting that Tat cannot activate a complete angiogenic program in these cells, unless FGF-2 is present. Tat stimulated SC growth only when the cells were cultured at low density and this correlated with the induction of tyrosine phosphorylation of various substrates, among which was erk-2, which mediates mitogenic signaling. The inhibition of SC growth in high cell density culture by Tat could be circumvented by the addition of FGF-2. We conclude that (i) the response of SC to Tat is density dependent and (ii) the angiogenic effect of Tat on both MEC and SC requires the presence of FGF-2.

Interleukin-6 family cytokines: signaling and effects in human airway smooth muscle cells

Interleukin (IL)-1β induces cyclooxygenase (COX)-2 expression and prostanoid formation in cultured human airway smooth muscle (HASM) cells. In other cell types, IL-6 family cytokines induce COX-2 or augment IL-1β-induced COX-2 expression. The purpose of this study was to determine whether IL-6 family cytokines were involved in COX-2 expression in HASM cells. RT-PCR was used to demonstrate that the necessary receptor components for IL-6-type cytokine binding are expressed in HASM cells. IL-6 and oncostatin M (OSM) each caused a dose-dependent phosphorylation of signal transducer and activator of transcription-3, whereas IL-11 did not. IL-6, IL-11, and OSM alone had no effect on COX-2 expression. However, OSM caused dose-dependent augmentation of COX-2 expression and prostaglandin (PG) E2release induced by IL-1β. In contrast, IL-6 and IL-11 did not alter IL-1β-induced COX-2 expression. IL-6 did increase IL-1β-induced PGE2formation in unstimulated cells but not in cells stimulated with arachidonic acid (AA; 10−5M), suggesting that IL-6 effects were mediated at the level of AA release. Our results indicate that IL-6 and OSM are capable of inducing signaling in HASM cells. In addition, OSM and IL-1β synergistically cause COX-2 expression and PGE2release.

Oncostatin M stimulates the growth of dermal fibroblasts via a mitogen-activated protein kinase-dependent pathway

Oncostatin M (OSM), a member of the hemopoietic cytokine family, has been implicated in the process of fibrosis and dermal wound healing. As a part of an ongoing study of the mechanisms of fibrosis and dermal wound healing, we have investigated the mechanism of the growth regulation of dermal fibroblasts by OSM. OSM stimulates the mitogenesis of dermal fibroblasts in a dose-dependent manner. This effect was completely blocked by anti-OSM IgG, but not by anti-IL-6 IgG. Furthermore, OSM induction was abolished by genistein, a tyrosine kinase inhibitor, or by PD98059, a specific mitogen-activated protein (MAP) kinase pathway inhibitor, but not by calphostin C, a protein kinase C inhibitor. Immunoblotting analysis using a specific Ab against phosphorylated MAP kinase (Thr202/Tyr204) showed that OSM induces phosphorylation of MAP kinase in dermal fibroblasts. Furthermore, transient transfection of the dominant-negative mutant MAP kinase into dermal fibroblasts abolished the OSM induction. These results strongly suggest that OSM stimulates the growth of dermal fibroblasts via a MAP kinase-dependent pathway.

Induction of angiotensin-converting enzyme by oncostatin m in human endothelial cells

OBJECTIVE

To examine the role of oncostatin M (OSM) in the regulation of angiotensin converting enzyme (ACE) in endothelial cells.

METHODS

Cultured endothelial cells were incubated with OSM (25-200 pM) for 24 h. Incubations were performed without or with the tyrosine kinase inhibitor, herbimycin (87 nM), or the selective MAP kinase kinase inhibitor, PD98059 (50 microM). ACE amount in intact endothelial cells was measured by an inhibitor binding assay and ACE mRNA levels by RNase protection assay.

RESULTS

OSM caused a dose dependent increase in ACE amount and increased the expression of ACE mRNA. The stimulatory effect of OSM was inhibited by pretreatments with herbimycin or PD98059.

CONCLUSIONS

OSM induced ACE in cultured HUVECs. Tyrosine kinase and MAPK activation were probably involved in ACE induction. Local induction of ACE by OSM in the vascular wall may be a consequence of inflammatory processes leading to locally increased production of angiotensin II and breakdown of bradykinin.

Oncostatin M induces interleukin-6 and cyclooxygenase-2 expression in human vascular smooth muscle cells : synergy with interleukin-1beta

Oncostatin M (OSM), a cytokine first identified from activated monocytes and T lymphocytes, is one of the most potent autocrine growth factor for AIDS and Kaposi's sarcoma. Little is known about the effects of OSM on normal vascular cells. We thus exposed human aortic smooth muscle cells (hASMCs) to OSM, examined cell proliferation and morphology, and determined interleukin-6 (IL-6) and cyclooxygenase-2 (COX-2) expression. OSM had a weak antiproliferative effect. After a 4-day incubation with 100 ng/mL OSM, cell count decreased to 69+/-3% of control. However, OSM induced striking changes in hASMC morphology, characterized by a polyclonal shape, in contrast to the spindle morphological feature of control hASMCs. OSM stimulated the release of IL-6 by hASMCs in a dose-dependent way; after a 48-hour exposure, values were 8.5+/-0.7, 29.7+/-3.5, 50.9+/-4.4, and 73.8+/-7.6x10(3) U/mL (n=6) at OSM concentrations of 0, 1, 10, and 100 ng/mL, respectively. OSM induced marked expression of COX-2 protein and mRNA. Leukemia inhibitory factor had no effect on hASMCs, indicating that OSM effects on hASMCs were mediated by the OSM type II receptor and not by the leukemia inhibitory factor receptor. OSM used the JAK/STAT signaling pathway, as demonstrated by rapid phosphorylation of JAK1 and specific activation of STAT1. Interestingly, OSM acted in synergy with IL-1beta on IL-6 production and COX-2 expression. In conclusion, OSM is a novel regulator of human smooth muscle cell functions, acting in concert with IL-1beta, and OSM may play a role in major vascular diseases such as atherosclerosis.

Oncostatin M induces angiogenesis in vitro and in vivo

Neovascularization of the atherosclerotic plaque is responsible for its weakening and consequently for the complications of vascular disease. Macrophages are a source of growth factors that can modulate angiogenesis. In this study, we analyzed the effect of oncostatin M (OSM) on angiogenesis, as it could be involved in the development of atherosclerosis. The effect of OSM was compared with those of leukemia inhibitory factor (LIF) and interleukin-6 (IL-6). On human dermal microvasculature endothelial cells (HMEC-1s), OSM (22.5 to 112.5 pmol/L) induced a dose-dependent increase in cell proliferation greater than that induced by the classic angiogenic factors vascular endothelial growth factor (VEGF; 543 pmol/L) and basic fibroblast growth factor (bFGF; 1.1 nmol/L). LIF (19 to 475 pmol/L) induced only a 30% increase in cell proliferation, and IL-6 had no effect. Furthermore, in a modified Boyden-chamber model, OSM, LIF, and IL-6 were chemoattractant for HMEC-1s. In a tridimensional gel of fibrin, OSM increased tube formation and tube length, which were already noticeable by day 3. LIF and IL-6 induced a weaker effect that was only obvious by day 10. The angiogenic effect of OSM was also demonstrated in vivo in a rabbit corneal model: OSM was more potent than LIF, the length of the neovessels being longer with OSM than with LIF, whereas IL-6 was without effect. We tested factors that could be involved in the proliferative effect of OSM on HMEC-1s. OSM induced only a slight increase in the urokinase receptor and a 60% increase in VEGF secretion, whereas it does not modify IL-8 secretion or bFGF levels. The effect of OSM seems to depend on endothelial cell origin and cell species: OSM (up to 112.5 pmol/L) did not induce human umbilical vein endothelial cell proliferation and even had a small inhibitory effect (17%) on calf pulmonary artery endothelial cells. In conclusion, OSM induces an angiogenic effect on capillary endothelial cells, which could be, at least in part, implicated in pathological processes such as atherosclerosis or tumor growth.

Implication of TNF Receptor-I-Mediated Extracellular Signal-Regulated Kinases 1 and 2 (ERK1/2) Activation in Growth of AIDS-Associated Kaposi’s Sarcoma Cells: A Possible Role of a Novel Death Domain Protein MADD in TNF-α-Induced ERK1/2 Activation in Kaposi’s Sarcoma Cells

TNF-α is a key pathogenic mediator of infectious and inflammatory diseases. HIV infection stimulates and dysregulates the immune system, leading to abnormal production of TNF-α. Despite its cytotoxic effect on some tumor cell lines, TNF-α functions as a growth stimulator for Kaposi’s sarcoma (KS), a common malignancy in HIV-infected patients. However, signaling pathways linked to TNF-α-induced mitogenic responses are not well understood. We found that extracellular signal-regulated kinases 1 and 2 (ERK1/2) in KS cells were significantly activated by TNF-α through tyrosine/threonine phosphorylation. Using neutralizing anti-TNFR-I and TNFR-II mAbs, we have now obtained evidence that TNF-α-induced KS cell growth and ERK1/2 activation are mediated exclusively by TNFR-I, not by TNFR-II. A selective inhibitor for ERK1/2 activator kinases, PD98059, profoundly inhibited not only the activation of ERK1/2, but also the TNF-α-induced KS cell proliferation. We therefore propose that the TNFR-I-ERK1/2 pathway plays a pivotal role in transmitting to KS cells the mitogenic signals of TNF-α. TNFR-I possesses no intrinsic kinase activity, suggesting that TNFR-I-associated proteins may provide a link between TNFR-I and ERK1/2 activation. We found that actinomycin D treatment of KS cells selectively abolished expression of mitogen-activated protein kinase-activating death domain protein (MADD), a novel TNFR-I-associated death domain protein. TNF-α failed to induce ERK1/2 activation in the actinomycin D-treated cells. MADD may couple TNFR-I with the ERK1/2 signaling pathway required for KS cell proliferation.

Different early effets of tyrphostin AG957 and geldanamycins on mitogen-activated protein kinase and p120cbl phosphorylation in anti CD-3-stimulated T-lymphoblasts

AG957, a tyrphostin tyrosine kinase inhibitor, has been shown previously to inhibit p210(bcr-abl) phosphorylation with concurrent inhibition of p210(bcr-abl)-expressing K562 cell growth (Kaur G and Sausville EA, Anticancer Drugs 7: 815-824, 1996). To assess the specificity of the action of AG957, we have examined its effect in another tyrosine kinase-mediated system, anti CD-3-stimulated Jurkat T Acute Lymphoblastic Leukemia cells. We also compared the effects of AG957 with those of geldanamycin, which can disrupt tyrosine kinase signaling through binding to heat shock protein (hsp90), and two geldanamycin analogs, 17-amino-17-demethoxygeldanamycin (17AG) and 17-allylamino-17-demethoxygeldanamycin (17AAG). At concentrations found to produce 90% inhibition of Jurkat T-cell growth, AG957 within 4 hr of addition inhibited mitogen-activated protein (MAP) kinase activation and activity, as shown by a decreased anti CD-3-stimulated erk-2 mobility shift in lysates of treated cells and a decrease in the stimulated myelin basic protein peptide kinase activity in erk-2 immunoprecipitates, respectively. AG957 did not inhibit this activity when added directly to immunoprecipitates. Effects in cells were found to be accompanied by a decrease in the anti CD-3-stimulated phosphorylation of p120cbl. Under conditions of a similar degree of growth inhibition, geldanamycin initially did not inhibit MAP kinase activation. Geldanamycin analogs did not decrease anti CD-3-induced cbl phosphorylation, but did reduce basal p120cbl tyrosine phosphorylation. The action of AG957 occurred with an apparent shift of several tyrosine-phosphorylated proteins to apparent higher molecular weights, which also did not occur with the geldanamycins. These results suggest that growth inhibition by AG957 can alter tyrosine kinase signaling systems unrelated to p210(bcr-abl) with a prominent early effect on MAP kinase activation in T-lymphoblasts. AG957 and geldanamycin affect tyrosine kinase signaling by distinct mechanisms.

Oncostatin M Up-Regulates Tissue Inhibitor of Metalloproteinases-3 Gene Expression in Articular Chondrocytes via De Novo Transcription, Protein Synthesis, and Tyrosine Kinase- and Mitogen-Activated Protein Kinase-Dependent Mechanisms

Cytokines and growth factors regulate physiologic and pathologic turn-over of cartilage extracellular matrix (ECM) by altering the balance between tissue inhibitors of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs). Oncostatin M (OSM) is a cytokine of the IL-6 family whose levels are increased in the serum and synovial fluids of patients with rheumatoid arthritis. We examined responsiveness of the TIMP-3 gene to OSM in articular chondrocytes and studied the regulatory and signaling mechanisms of this response. OSM induced TIMP-3 mRNA and protein expression in a dose- and time-dependent fashion. Concomitantly, stromelysin-1 and collagenase-1 RNA and activities were also induced. A cartilage matrix growth factor, TGF-β, induced TIMP-3, but combined OSM and TGF-β did not further increase the extent of induction, suggesting a lack of synergy between the two. OSM induction of TIMP-3 gene expression was dependent upon de novo protein synthesis and transcription. RNA decay time-courses suggested that the OSM-mediated increase of TIMP-3 RNA was not due to enhanced message stability and, along with inhibition by actinomycin-D, suggested a transcriptional control. The antiinflammatory glucocorticoid, dexamethasone, down-regulated this augmentation. Investigation of the signaling mechanisms revealed that protein tyrosine kinase inhibitors genistein and herbimycin A, as well as the specific mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059, suppressed OSM-induced TIMP-3 message expression, suggesting the involvement of tyrosine kinases and mitogen-activated protein kinase cascades in the signaling of OSM leading to TIMP-3 RNA enhancement. Thus OSM can potentially alter the cartilage matrix metabolism by regulating genes like TIMP-3 and matrix metalloproteinases.

Fibronectin modulates the effects of HIV-1 Tat on the growth of murine Kaposi's sarcoma-like cells through the down-regulation of tyrosine phosphorylation

HIV-1 Tat plays a role in the pathogenesis of Kaposi's sarcoma. We therefore investigated the effect of Tat on the growth of murine Kaposi's sarcoma-like spindle (TTB) cells derived from dermal lesions. We observed that Tat and a peptide corresponding to the carboxyl-terminal region (Tat65-80) containing an RGD sequence inhibit TTB cell proliferation only when cells are cultured on fibronectin. This inhibitory effect correlates with redistribution of the alpha(v) integrin subunit on the surface of TTB cells and with down-regulation of tyrosine phosphorylation of specific substrates due to an increased tyrosine phosphatase activity. Indeed, phenylarsine oxide, a potent inhibitor of phosphotyrosine phosphatases, prevented the effects of Tat on TTB cells. We therefore argue that the action of Tat on TTB cells is mediated by the RGD motif through an integrin-based cell signaling pathway involving the activity of phosphotyrosine phosphatase(s), which would lead to a decrease in the levels of phosphotyrosine-containing proteins, among which is erk-2/p42MAPK.

Oncostatin M stimulates c-Fos to bind a transcriptionally responsive AP-1 element within the tissue inhibitor of metalloproteinase-1 promoter

Tissue inhibitor of metalloproteinases-1 (TIMP-1) can be regulated by gp130 cytokines such as IL-6 and oncostatin M (OSM). Polymerase chain reaction deletion analysis of the murine TIMP-1 proximal promoter in chloramphenicol acetyltransferase reporter gene constructs identified an AP-1 element (-59/-53) that allows maximal responsiveness to OSM in HepG2 cells. Fos and Jun nuclear factors bound constitutively to this site as identified by supershift analysis in electrophoretic mobility shift assays, and oncostatin M (but not IL-6) induced an additional "complex 2" that contained c-Fos and JunD. OSM stimulated a rapid and transient increase in c-Fos mRNA and nuclear protein that coincided with complex 2 formation. Phorbol 13-myristate 12-acetate could also induce c-Fos but could not regulate the TIMP-1 reporter gene constructs. Transfection studies also showed that 3'-deletion of sequences downstream of the transcriptional start site (+1/+47) markedly reduced OSM -fold induction. Nuclear factors bound to SP1 and Ets sequences were detected, but were not altered upon OSM stimulation. Although OSM and IL-6 induced STAT (signal transducers and activators of transcription) factors to bind a high affinity Sis-inducible element DNA probe, binding to homologous TIMP-1 promoter sequences was not detected. Thus, OSM (but not IL-6) stimulates c-Fos, which participates in maximal activation of TIMP-1 transcription, likely in cooperation with other factors such as SP1 or as yet unidentified mechanisms involving the +1 to +47 region of the promoter.

Inhibition of growth and induction of differentiation of glioma cell lines by oncostatin M (OSM)

The neuropoietic cytokines of the interleukin-6 family are a group of structurally and functionally related polypeptides. We studied the effect of the multifunctional neuropoietic cytokines, including oncostatin M (OSM), leukemia inhibitory factor (LIF) and interleukin-6 (IL-6), on anaplastic glioma cell lines. Growth and morphology of the glioma cell lines were affected differently. While IL-6 and LIF exerted no or only small minor morphological changes and growth retardation, OSM induced a marked change in morphology and a strong suppression of growth. OSM treated cells were characterized by enlargement and the formation of multiple, thin processes thus resembling mature cultured astrocytes. The growth inhibitory effects were dose dependent with a maximum exerted by addition of 50 ng/ml OSM. The inhibition of DNA synthesis by OSM could be abolished by antibodies blocking either the activity of OSM or the OSM-receptor component, gp130.

Inflammatory cytokines induce the expression of basic fibroblast growth factor (bFGF) isoforms required for the growth of Kaposi's sarcoma and endothelial cells through the activation of AP-1 response elements in the bFGF promoter

BACKGROUND

The growth of Kaposi's sarcoma (KS) spindle cells is dependent on a number of inflammatory cytokines as well as the autocrine growth factor, basic fibroblast growth factor (bFGF). Moreover, inflammatory cytokines, found at increased levels in KS lesions, promote bFGF production in KS and endothelial cells.

OBJECTIVES

To determine the induction of bFGF isoforms, role of bFGF in cell growth and activation of the bFGF promoter by inflammatory cytokines.

DESIGN AND METHOD

3H-Thymidine uptake, bFGF immunoblotting and transfection of dominant-negative MAP kinase components were used to study the effect of cytokines on the bFGF promoter, bFGF isoform expression and proliferation of KS cells.

RESULTS

Treatment with oncostatin M (OSM), interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha induced the expression of 18, 22 and 24 kDa bFGF isoforms in KS and human umbilical vein endothelial cells (HUVEC). Antisense bFGF oligonucleotides interfered in the induction of KS cell proliferation by individual cytokines. OSM, IL-1 and TNF-alpha induced the transcriptional activation of a bFGF promoter reporter gene in parallel with the activation of an AP-1 reporter. Dominant-negative ERK and dominant-negative JNK mutants interfered in cytokine-induced activation of these reporters in accordance with the role of the MAP kinase cascades in individual cytokine signaling pathways.

CONCLUSIONS

OSM, IL-1 and TNF-alpha induce KS cell growth by inducing the expression of various bFGF isoforms. Moreover, bFGF production by KS and HUVEC is dependent on the activation of the ERK and JNK cascades, which result in the transcriptional activation of the bFGF promoter.

Oncostatin M stimulates transcription of the human alpha2(I) collagen gene via the Sp1/Sp3-binding site

Oncostatin M (OSM), a member of the hematopoietic cytokine family, has been implicated in excessive bone growth and in the process of fibrosis. As part of an ongoing study of the molecular mechanisms of fibrosis, we have investigated the transcriptional regulation of the alpha2(I) collagen gene by OSM in human fibroblasts. An OSM response element was mapped by deletional analysis between base pairs (bp) -148 and -108 in the alpha2(I) collagen promoter. Further functional analysis of the alpha2(I) collagen promoter containing various substitution mutations revealed that both the basal activity and OSM stimulation of this promoter are mediated by a TCCTCC motif located between bp -128 and -123. Furthermore, three copies of the 12-bp synthetic alpha2(I) collagen promoter fragment containing the "TCC" motif conferred OSM inducibility to the otherwise unresponsive thymidine kinase promoter. Electrophoretic mobility shift assays demonstrated that the TCCTCC motif constitutes a novel binding site for the transcription factors Sp1 and Sp3. No differences have been observed in in vitro gel shift binding assays between unstimulated and OSM-stimulated fibroblasts. However, subtle conformational changes were detected in the region of the promoter surrounding TCC repeats after OSM stimulation using in vivo footprint analysis. In conclusion, this study characterized a dual-function response element that mediates the basal activity and OSM stimulation of the human alpha2(I) collagen promoter.

Characterization of Signal Transduction Pathways in Human Bone Marrow Endothelial Cells

Human bone marrow endothelial cells immortalized with the T antigen of SV40 (TrHBMEC) have previously been characterized by us with regard to their properties that are similar to primary marrow endothelial cells and their utility as a model system. We now report that TrHBMEC express a recently discovered signal transduction molecule termed RAFTK (related adhesion focal tyrosine kinase), also called Pyk2 or CAK-β. RAFTK, the second member of the focal adhesion kinase (FAK) family, is known to be activated in response to calcium flux in neuronal cells and integrin stimulation in megakaryocytes and B cells. We have studied the effects of cytokines on RAFTK activation in TrHBMEC. Treatment of TrHBMEC with the vascular endothelial growth factor (VEGF ), as well as the VEGF-related protein (VRP), the recently identified ligand for the FLT-4 receptor, resulted in enhanced tyrosine phosphorylation of RAFTK. Similar changes in RAFTK phosphorylation were observed upon stimulation of TrHBMEC with basic fibroblast growth factor (bFGF ) or oncostatin M (OSM). Stimulation of these cells with growth factors also resulted in an increase in RAFTK activity and the c-Jun NH2 -terminal kinase (JNK). RAFTK coimmunoprecipitated with the cytoskeletal protein paxillin through its C-terminal proline-rich domain in TrHBMEC. These results suggest that, in marrow endothelium, activation of RAFTK by VEGF, VRP, OSM, and bFGF represents a new element in the signal transduction pathways used by these growth factors and likely acts to coordinate signaling from their surface receptors to the cytoskeleton, thereby modulating cell growth and function.

Characterization of Signal Transduction Pathways in Human Bone Marrow Endothelial Cells

Human bone marrow endothelial cells immortalized with the T antigen of SV40 (TrHBMEC) have previously been characterized by us with regard to their properties that are similar to primary marrow endothelial cells and their utility as a model system. We now report that TrHBMEC express a recently discovered signal transduction molecule termed RAFTK (related adhesion focal tyrosine kinase), also called Pyk2 or CAK-β. RAFTK, the second member of the focal adhesion kinase (FAK) family, is known to be activated in response to calcium flux in neuronal cells and integrin stimulation in megakaryocytes and B cells. We have studied the effects of cytokines on RAFTK activation in TrHBMEC. Treatment of TrHBMEC with the vascular endothelial growth factor (VEGF ), as well as the VEGF-related protein (VRP), the recently identified ligand for the FLT-4 receptor, resulted in enhanced tyrosine phosphorylation of RAFTK. Similar changes in RAFTK phosphorylation were observed upon stimulation of TrHBMEC with basic fibroblast growth factor (bFGF ) or oncostatin M (OSM). Stimulation of these cells with growth factors also resulted in an increase in RAFTK activity and the c-Jun NH2 -terminal kinase (JNK). RAFTK coimmunoprecipitated with the cytoskeletal protein paxillin through its C-terminal proline-rich domain in TrHBMEC. These results suggest that, in marrow endothelium, activation of RAFTK by VEGF, VRP, OSM, and bFGF represents a new element in the signal transduction pathways used by these growth factors and likely acts to coordinate signaling from their surface receptors to the cytoskeleton, thereby modulating cell growth and function.

Human herpesvirus 8 and Kaposi's sarcoma

In the last 2 years, the discovery that the suspected causative agent of Kaposi's sarcoma (KS) is a new gamma-herpesvirus, called human herpesvirus type 8 (HHV8) or Kaposi's sarcoma-associated herpesvirus (KSHV), has been followed by studies showing it to be a sine qua non of all clinical forms of KS and a specific marker for KS in the differential diagnosis of angioproliferative lesions. Reports that the virus is ubiquitous have been based on the polymerase chain reaction and appear to be contradicted by serological studies of blood donors and patients with acquired immunodeficiency syndrome (AIDS)-related and classical KS. Further serological surveys and the application of molecular probes in histological sections should resolve the issue. The recent descriptions of KSHV RNA molecules and several viral mimickers of human cytokines offer the chance to map the viral latent-lytic cycle and will change the direction of cytokine research in KS. These discoveries suggest that the increase of endemic classical KS noted in Nordic countries before the AIDS epidemic was due to spread of KSHV by unknown routes. The aggregate data should force a paradigm shift away from the notion that human immunodeficiency virus infection has a necessary role to play in AIDS-KS other than as a cause of progressive immunodeficiency.

Oncostatin M is a proinflammatory mediator. In vivo effects correlate with endothelial cell expression of inflammatory cytokines and adhesion molecules

Oncostatin M is a member of the IL-6 family of cytokines that is primarily known for its effects on cell growth. Endothelial cells have an abundance of receptors for oncostatin M, and may be its primary target. We determined if oncostatin M induces a key endothelial cell function, initiation of the inflammatory response. We found that subcutaneous injection of oncostatin M in mice caused an acute inflammatory reaction. Oncostatin M in vitro stimulated: (a) polymorphonuclear leukocyte (PMN) transmigration through confluent monolayers of primary human endothelial cells; (b) biphasic PMN adhesion through rapid P-selectin expression, and delayed adhesion mediated by E-selectin synthesis; (c) intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 accumulation; and (d) the expression of PMN activators IL-6, epithelial neutrophil activating peptide-78, growth-related cytokine alpha and growth-related cytokine beta without concomitant IL-8 synthesis. The nature of the response to oncostatin M varied with concentration, suggesting high and low affinity oncostatin M receptors independently stimulated specific responses. Immunohistochemistry showed that macrophage-like cells infiltrating human aortic aneurysms expressed oncostatin M, so it is present during a chronic inflammatory reaction. Therefore, oncostatin M, but not other IL-6 family members, fulfills Koch's postulates as an inflammatory mediator. Since its effects on endothelial cells differ significantly from established mediators like TNFalpha, it may uniquely contribute to the inflammatory cycle.

Cytokine signaling through the novel tyrosine kinase RAFTK in Kaposi's sarcoma cells

A number of cytokines, including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), oncostatin M (OSM), IL-6, and tumor necrosis factor alpha (TNF-alpha), have been postulated to have a role in the pathogenesis of Kaposi's sarcoma (KS). The proliferative effects of bFGF and OSM may be via their reported activation of the c-Jun NH2-terminal kinase (JNK) signaling pathway in KS cells. We now report that KS cells express a recently identified focal adhesion kinase termed RAFTK which appears in other cell systems to coordinate surface signals between cytokine and integrin receptors and the cytoskeleton as well as act downstream to modulate JNK activation. We also report that the tyrosine kinase receptor FLT-4, present on normal lymphatic endothelium, is robustly expressed in KS cells. Treatment of KS cells with VEGF-related protein (VRP), the ligand for the FLT-4 receptor, as well as with the cytokines bFGF, OSM, IL-6, VEGF, or TNF-alpha resulted in phosphorylation and activation of RAFTK. Following its activation, there was an enhanced association of RAFTK with the cytoskeletal protein paxillin. This association was mediated by the hydrophobic COOH-terminal domain of the kinase. Furthermore, JNK activity was increased in KS cells after VEGF or VRP stimulation. We postulate that in these tumor cells RAFTK may be activated by a diverse group of stimulatory cytokines and facilitate signal transduction to the cytoskeleton and downstream to the growth promoting JNK pathway.

Human herpesvirus 8 encodes a homolog of interleukin-6

Kaposi's sarcoma is a multifocal lesion that is reported to be greatly influenced by cytokines such as interleukin-6 (IL-6) and oncostatin M. DNA sequences of a novel human gammaherpesvirus, termed human herpesvirus 8 (HHV-8) or Kaposi sarcoma-associated herpesvirus, have been identified in all epidemiological forms of Kaposi's sarcoma with high frequency. The presence of HHV-8 DNA is also clearly associated with certain B-cell lymphomas (body cavity-based lymphomas) and multicentric Castleman's disease. Sequence analysis of a 17-kb fragment revealed that adjacent to a block of conserved herpesvirus genes (major DNA-binding protein, glycoprotein B, and DNA polymerase), the genome of HHV-8 encodes structural homolog of IL-6. This cytokine is involved not only in the pathogenesis of Kaposi's sarcoma but also in certain B-cell lymphomas and multicentric Castleman's disease. The viral counterpart of IL-6 (vIL-6) has conserved important features such as cysteine residues involved in disulfide bridging or an amino-terminal signal peptide. Most notably, the region known to be involved in receptor binding is highly conserved in vIL-6. This conservation of essential features and the remarkable overlap between diseases associated with HHV-8 and diseases associated with IL-6 disregulation clearly suggest that vIL-6 is involved in HHV-8 pathogenesis.

AIDS-related Kaposi's sarcoma. A template for the translation of molecular pathogenesis into targeted therapeutic approaches

AIDS-related Kaposi's sarcoma (KS) represents a complex interaction of host and viral factors. There are a number of fundamental questions surrounding the interplay between the disparate factors that can contribute to the pathogenesis and pathophysiology of this disease. Targets such as the enhancement of immune function, inhibition of angiogenic factors or immunostimulatory cytokines, inhibition of viral proteins such as Tat, or hormonal manipulations are now or will in the future become the focus of research to develop innovative anti-KS therapy and prevention measures. Antiviral approaches aimed at HIV or other viruses may potentially target a number of steps in KS pathogenesis. This article reviews diverse modalities--cytotoxic, antiviral, gene-directed, growth factor-targeted, and antiangiogenesis--that singly, or more likely in combination, stand to make an impact on the cure and prevention of AIDS-related KS.

Pathogenesis of AIDS--related Kaposi's sarcoma. Evidence of a viral etiology

Kaposi's sarcoma is the most common malignancy in patients with HIV infection. New studies point to the involvement of a new human Kaposi's sarcoma herpes virus (KSHV) as a transforming agent. After transformation, cytokine perturbations facilitate growth and in some cases clonal growth occurs. This results in a malignancy with devastating clinical consequences. A clear understanding of the mechanism of transformation by KSHV will lead to better therapies.

Characterization of the structure and function of a new mitogen-activated protein kinase (p38beta)

Mitogen-activated protein (MAP) kinase cascades represent one of the major signal systems used by eukaryotic cells to transduce extracellular signals into cellular responses. Four MAP kinase subgroups have been identified in humans: ERK, JNK (SAPK), ERK5 (BMK), and p38. Here we characterize a new MAP kinase, p38beta. p38beta is a 372-amino acid protein most closely related to p38. It contains a TGY dual phosphorylation site, which is required for its kinase activity. Like p38, p38beta is activated by proinflammatory cytokines and environmental stress. A comparison of events associated with the activation of p38beta and p38 revealed differences, most notably in the preferred activation of p38beta by MAP kinase kinase 6 (MKK6), whereas p38 was activated nearly equally by MKK3, MKK4, and MKK6. Moreover, in vitro and in vivo experiments showed a strong substrate preference by p38beta for activating transcription factor 2 (ATF2). Enhancement of ATF2-dependent gene expression by p38beta was approximately20-fold greater than that of p38 and other MAP kinases tested. The data reported here suggest that while closely related, p38beta and p38 may be regulated by differing mechanisms and may exert their actions on separate downstream targets.

Interleukin 4 or oncostatin M induces a prolonged increase in P-selectin mRNA and protein in human endothelial cells

During acute inflammation, P-selectin is transiently mobilized from Weibel-Palade bodies to the surface of histamine-activated endothelial cells, where it mediates rolling adhesion of neutrophils under hydrodynamic flow. During chronic or allergic inflammation, sustained expression of P-selectin on the endothelial cell surface has been observed. We found that the cytokines interleukin 4 (IL-4) or oncostatin M (OSM) induced a five- to ninefold increase in P-selectin messenger RNA (mRNA) in human umbilical vein endothelial cells (HUVEC) that persisted as long as 72 h. IL-4 elevated P-selectin mRNA by increasing its transcription rate rather than by prolonging its already long half-life. Stimulation of P-selectin transcription by IL-4 or OSM required new protein synthesis and tyrosine phosphorylation of cellular proteins. Tumor necrosis factor alpha, IL-1 beta, lipopolysaccharide, or IL-3 did not increase P-selectin mRNA in HUVEC, and did not augment the IL-4-induced increase in P-selectin transcripts. IL-4 or OSM increased P-selectin protein on the cell surface as well as in Weibel-Palade bodies. Under flow conditions, neutrophils rolled on P-selectin expressed by IL-4-treated HUVEC, and even more neutrophils rolled on P-selectin after IL-4-treated HUVEC were stimulated with histamine. These data demonstrate that IL-4 or OSM stimulates endothelial cells to synthesize more P-selectin over prolonged periods. The increased expression of P-selectin may facilitate the emigration of leukocytes into sites of chronic or allergic inflammation.

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.

Oncostatin M induces association of Grb2 with Janus kinase JAK2 in multiple myeloma cells

Oncostatin M (OSM) is a 28-kD glycoprotein recently identified as a growth factor for human multiple myeloma cells. It belongs to a family of distantly related cytokines that includes interleukin 6, ciliary neurotrophic factor, leukemia-inhibitory factor, and interleukin 11. These cytokines initiate signaling by inducing either homodimerization of gp130 or heterodimerization of gp130 with leukemia-inhibitory factor receptor beta components. Such dimerization in turn activates receptor-associated tyrosine kinases. In the present study using U266B1 human multiple myeloma cells, we show that OSM induces tyrosine phosphorylation and activation of JAK2, but not JAK1 or Tyk2, kinases. The results also demonstrate that OSM induces direct interaction of JAK2 kinase with Grb2, an SH2/SH3 domain containing adaptor protein. The SH2 domain of Grb2 is directly associated with tyrosine-phosphorylated JAK2. Furthermore, the presence of Sos in the JAK2-Grb2 complex suggests a role for Ras in OSM-transduced signaling.

The signal transduction pathway of erythropoietin involves three forms of mitogen-activated protein (MAP) kinase in UT7 erythroleukemia cells

The survival and proliferation of the UT-7 human leukemic cell line is strictly dependent on the presence of either interleukin 3, granulocyte-macrophage colony-stimulating factor or erythropoietin. In these cells, erythropoietin stimulation led to the rapid phosphorylation of several proteins including the erythropoietin receptor and proteins with molecular masses around 45 kDa which could be mitogen-activated protein (MAP) kinases. Separation of cytosol from resting or erythropoietin-stimulated UT-7 cells by anion-exchange chromatography revealed two peaks of myelin basic protein kinase activity. The kinase activity of the first peak was independent of erythropoietin treatment of the cells and corresponded to an unidentified 50-kDa kinase, whereas the second peak was only present in erythropoietin-stimulated cells and corresponded to three forms of MAP kinases with molecular masses of 45, 44 and 42 kDa. The three forms were separated by hydrophobic chromatography and were shown to be activated in erythropoietin-stimulated cells. The 44-kDa and 42-kDa forms corresponded to extracellular signal-regulated kinase (ERK)-1 and ERK-2, respectively. Evidence was obtained showing that the 45-kDa form is not a shifted form of ERK-1 but corresponded to a less well defined form of MAP kinase which may be the previously described ERK-4. MAP kinase activation was detected after 1 min erythropoietin stimulation and remained detectable after more than 1 hour. A role for MAP kinase activation in erythropoietin-stimulated cell proliferation was suggested by the simultaneous inhibition of erythropoietin-induced MAP kinase stimulation and cell proliferation. The potential activator of MAP kinase, RAF-1, was hyperphosphorylated in erythropoietin-stimulated cells and its autophosphorylation activity was strongly increased. The protein adaptor Shc was heavily phosphorylated in UT-7 erythropoietin-stimulated cells and associated strongly with a unidentified 145-kDa protein. However, Shc bound poorly to the activated erythropoietin receptor and most Shc proteins were cytosolic in both unstimulated and erythropoietin-stimulated cells. In contrast, Grb2 associated efficiently with the activated erythropoietin receptor and a significant part of Grb2 was associated to a particulate subcellular fraction upon erythropoietin stimulation.

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.

Activation of extracellular signal-regulated protein kinase (ERK/MAP kinase) following CD28 cross-linking: activation in cells lacking p56lck

T lymphocytes require two signals for activation. Recognition of antigen/MHC complexes by the T cell receptor delivers the first signal, while a second signal, delivered by the cell surface receptors CD80 and/or CD86 binding to the T cell surface molecule CD28, has been shown to be effective for the initiation of effective T cell responses. While some of the cytoplasmic effector molecules involved in T cell receptor signaling is known, little is known regarding those involved in the co-stimulation of T cells by CD28. Using the T cell leukemic cell line Jurkat as a model for T cell activation, we demonstrate that cross-linking CD28 using monoclonal antibodies causes tyrosine phosphorylation and activation of MAP kinase/ERK. This activation was rapid, peaking at approximately 5 minutes post CD28 cross-linking, and transient. Activation of MAP kinase/ERK occurred 3 fold less efficiently in a Jurkat line lacking functional p56lck (JCAM.1), and was almost undetectable in a line lacking CD45 (J45.01). These results suggest that CD28 cross-linking can activate intracellular signaling pathways via several different tyrosine kinases. Thus CD28 signaling can activate src family kinases lck and fyn, as well as the Tec family kinase emt/itk. Activation of any one or a combination of these tyrosine kinases may be sufficient for the activation of MAPK following CD28 cross-linking. Activation of MAPK has been shown to cause activation of AP-1 and other transcription factors via serine and/or threonine phosphorylation.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic assay for genistein in biological fluids

A specific, sensitive and technically convenient HPLC method for assaying genistein in biological fluids has been developed. The compound and 4-hydroxybenzophenone, added as an internal standard, were efficiently isolated from both plasma and urine by extraction with tert-butyl methyl ether. Following evaporation of the organic solvent, the extract was reconstituted with methanol-0.05 M ammonium acetate buffer, pH 4.7 (30:70, v/v), and loaded onto a 4 microns Nova-Pak C8 column (15 cm x 3.9 mm I.D.). Chromatography was performed at ambient temperature using a mobile phase of acetonitrile-0.05 M ammonium formate buffer, pH 4.0 (27:73, v/v), at a flow-rate of 1.0 ml/min, with UV detection at 260 nm. Mean values of the tR for the drug and internal standard, determined from chromatograms of the 1 microgram/ml plasma standard during a 6 month period, were 8.27 +/- 0.55 and 11.92 +/- 0.71 min, respectively (S.D., n = 29). With a sample volume of 50 microliters, the lowest concentration of genistein included in the plasma standard curve, 0.020 microgram/ml, was quantified with a 10.7% R.S.D. over a 5 month period. Plasma standards having concentrations of 0.050 to 1.02 micrograms/ml exhibited R.S.D. values ranging from 2.3 to 6.1%. The drug was quantified in urine with similar reproducibility. The sensitivity of the assay was adequate for characterizing the plasma pharmacokinetics of genistein in the mouse and dog. However, a 10-fold improvement in sensitivity was afforded by increasing the sample size to 250 microliters, without otherwise modifying the method. Thus, this procedure may prove suitable for determining plasma and urine levels of genistein in humans consuming dietary isoflavonoids in a much more convenient manner than permitted by existing methodology.