Oncostatin M as a potent mitogen for AIDS-Kaposi's sarcoma-derived cells

Natural products with anti-tumorigenesis potential targeting macrophage

BACKGROUND

Inflammation is a risk factor for tumorigenesis. Macrophage, a subset of immune cells with high plasticity, plays a multifaceted role in this process. Natural products, which are bioactive compounds derived from traditional herbs or foods, have exhibited diverse effects on macrophages and tumorigenesis making them a valuable resource of drug discovery or optimization in tumor prevention.

PURPOSE

Provide a comprehensive overview of the various roles of macrophages in tumorigenesis, as well as the effects of natural products on tumorigenesis by modulating macrophage function.

METHODS

A thorough literature search spanning the past two decades was carried out using PubMed, Web of Science, Elsevier, and CNKI following the PRISMA guidelines. The search terms employed included "macrophage and tumorigenesis", "natural products, macrophages and tumorigenesis", "traditional Chinese medicine and tumorigenesis", "natural products and macrophage polarization", "macrophage and tumor related microenvironment", "macrophage and tumor signal pathway", "toxicity of natural products" and combinations thereof. Furthermore, certain articles are identified through the tracking of citations from other publications or by accessing the websites of relevant journals. Studies that meet the following criteria are excluded: (1) Articles not written in English or Chinese; (2) Full texts were not available; (3) Duplicate articles and irrelevant studies. The data collected was organized and summarized based on molecular mechanisms or compound structure.

RESULTS

This review elucidates the multifaceted effect of macrophages on tumorigenesis, encompassing process such as inflammation, angiogenesis, and tumor cell invasion by regulating metabolism, non-coding RNA, signal transduction and intercellular crosstalk. Natural products, including vitexin, ovatodiolide, ligustilide, and emodin, as well as herbal remedies, have demonstrated efficacy in modulating macrophage function, thereby attenuating tumorigenesis. These interventions mainly focus on mitigating the initial inflammatory response or modifying the inflammatory environment within the precancerous niche.

CONCLUSIONS

These mechanistic insights of macrophages in tumorigenesis offer valuable ideas for researchers. The identified natural products facilitate the selection of promising candidates for future cancer drug development.

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.

Endemic Kaposi's Sarcoma

Kaposi's sarcoma (KS) is a common neoplasm in Eastern and central Africa reflecting the spread of human gammaherpesvirus-8 (HHV-8), now considered a necessary causal agent for the development of KS. The endemic KS subtype can follow an aggressive clinical course with ulcerative skin lesions with soft tissue invasion or even bone or visceral involvement. In the latter cases, a thorough imaging work-up and better follow-up schedules are warranted. As KS is a chronic disease, the therapeutic goal is to obtain sustainable remission in cutaneous and visceral lesions and a good quality of life. Watchful monitoring may be sufficient in localized cutaneous forms. Potential therapeutic modalities for symptomatic advanced KS include systemic chemotherapies, immunomodulators, immune checkpoint inhibitors, and antiangiogenic drugs.

Targeted plasma proteomics reveals upregulation of distinct inflammatory pathways in people living with HIV

Despite antiretroviral therapy (ART), people living with HIV (PLHIV) display persistent inflammation leading to non-AIDS-related co-morbidities. To better understand underlying mechanisms, we compared targeted plasma inflammatory protein concentration (n = 92) between a cohort of 192 virally suppressed PLHIV, who were followed-up for five years, and 416 healthy controls (HC). Findings were validated in an independent cohort of 649 virally suppressed PLHIV and 98 HC. Compared to HC, PLHIV exhibited distinctively upregulated inflammatory proteins, including mucosal defense chemokines, CCR5 and CXCR3 ligands, and growth factors. Unsupervised clustering of inflammatory proteins clearly differentiated PLHIV with low (n = 123) and high inflammation (n = 65), the latter having a 3.4 relative risk (95% confidence interval 1.2-9.8) to develop malignancies and trend for cardiovascular events during a 5-year follow-up. The best protein predictors discriminating the two inflammatory endotypes were PD-L1, VEGFA, LAP TGF β-1, and TNFRSF9. Our data provide insights into co-morbidities associated inflammatory changes in PLHIV on long-term ART.

Primary nasal Kaposi Sarcoma in well-controlled HIV-positive patient with normal CD4 count associated with long-term nasal steroid use

Kaposi sarcoma (KS) is an angioproliferative disease that is caused by human herpesvirus 8. The epidemic form of KS is associated with acquired immunodeficiency syndrome (AIDS) and is common in HIV-positive patients with CD4 counts less than 200 cells/mm. We present the case of a 63-year-old man with well-controlled HIV and normal CD4 count developing atypical nasal KS associated with intranasal steroid use.

The role of oncostatin M receptor gene polymorphisms in bladder cancer

Background

Oncostatin M receptor (OSMR) represents a part of the interleukin-six (IL6) cytokine group that was discovered recently to be closely associated with cell’s growth and differentiation, inflammation, and enhancement of metastatic capacity. A comprehensive study suggests a close relationship between OSMR and papillary thyroid cancer, colorectal cancer, breast cancer, and other tumors. However, the relationship between OSMR and bladder cancer has yet to be determined.

Methods

Three hundred six patients (including 142 patients with muscle-invasive bladder cancer and 164 patients with non-muscle-invasive bladder cancer) as well as 459 normal controls were included in this study. Two tag SNPs of OSMR, rs2278329, and rs2292016 were genotyped by TaqMan® SNP Genotyping Assay method and then the associations with bladder cancer were analyzed, as well as risk factors and prognosis.

Results

Patients with bladder cancer and controls did not differ significantly in terms of genotype frequencies and allele frequency distribution of rs2278329 (P = 0.77, OR = 0.97) and rs2292016 (P = 0.39, OR = 1.20) respectively. For rs2278329, no differences were found in terms of risk factors in stratified analyses. However, rs2292016 was associated with recurrence and tumor grade. GT/TT was found to increase the risk of relapse compared to the patients without allele T (GG genotype) (P = 0.016, OR = 1.878, 95% CI = 1.12–3.14) with the T allele of rs2292016 being a risk factor for recurrence (P = 0.032, OR = 0.67, 95% CI = 0.47–0.97). Besides, patients with GT genotype often present with high-grade bladder cancer (P = 0.003, OR = 2.33, 95% CI = 1.32–4.17). Multiple Cox regression analysis showed that rs2278329 and rs2292016 were related to the recurrence-free survival and overall survival in non muscle invasive bladder cancer (NMIBC) patients. For rs2278329, GA genotype could affect recurrence-free survival (P = 0.01, OR = 2.16, 95% CI = 1.17–3.98). For rs2292016, TT/GT genotype had a lower risk of death compared with GG homozygote genotype, and T was a protective factor for overall survival in bladder cancer (P = 0.029, OR = 0.22, 95% CI = 0.06–0.86).

Conclusions

OSMR genotype frequencies were found to be associated with higher recurrence in bladder cancer, and it may serve as a biomarker candidate gene to predict prognosis of this disease. Further validation of OSMR as biomarker is required.

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.

Oncostatin M is overexpressed in skin squamous-cell carcinoma and promotes tumor progression

Cutaneous squamous cell carcinoma (cSCC) is the second most common keratinocyte malignancy and accounts for 20% of skin cancer deaths. Cancer is closely related to inflammation, but the contribution of the tumor microenvironment to cSCC development is poorly understood. We previously showed that oncostatin M (OSM), a cytokine belonging to the IL-6 family, promotes normal keratinocyte proliferation and migration, skin inflammation, and epidermal hyperplasia, both in vitro and in vivo. Here, we show that OSM is overexpressed in human cSCC and is associated with type 1 immune polarization. In vitro, OSM induced STAT-3 and ERK signaling, modified the expression of genes involved in cytokine signaling, proliferation, inhibition of apoptosis, and immune responses, and promoted proliferation and migration of malignant keratinocyte PDVC57 cells. PDVC57 cells grafted in the skin of mice led to rapid cSCC development, associated with OSM expression by tumor-infiltrating neutrophils. Finally, the absence of OSM (OSM-KO mice) led to a 30% reduction of tumor size and reduced M2 polarization in the tumor microenvironment. Globally, these results support a pro-tumoral role of OSM in cSCC development and suggest that a new therapeutic approach targeting this cytokine could be considered.

The RNA Epitranscriptome of DNA Viruses

RNA modifications have generated much interest in the virology field, as recent works have shown that many viruses harbor these marks and modify cellular marks. The most abundant mRNA modification in eukaryotic cells, N6-methyladenosine (m6A), has been examined extensively at the genome-wide scale in both cellular and viral contexts. This Gem discusses the role of m6A in gene regulation and describes recent advancements in Kaposi's sarcoma-associated herpesvirus (KSHV) and simian virus 40 (SV40) research. We provide insights into future research related to m6A in DNA viruses.

RNA epitranscriptomics: Regulation of infection of RNA and DNA viruses by N6 -methyladenosine (m6 A)

N⁶ -methyladenosine (m⁶ A) was discovered 4 decades ago. However, the functions of m⁶ A and the cellular machinery that regulates its changes have just been revealed in the last few years. m⁶ A is an abundant internal mRNA modification on cellular RNA and is implicated in diverse cellular functions. Recent works have demonstrated the presence of m⁶ A in the genomes of RNA viruses and transcripts of a DNA virus with either a proviral or antiviral role. Here, we first summarize what is known about the m⁶ A "writers," "erasers," "readers," and "antireaders" as well as the role of m⁶ A in mRNA metabolism. We then review how the replications of numerous viruses are enhanced and restricted by m⁶ A with emphasis on the oncogenic DNA virus, Kaposi sarcoma-associated herpesvirus (KSHV), whose m⁶ A epitranscriptome was recently mapped. In the context of KSHV, m⁶ A and the reader protein YTHDF2 acts as an antiviral mechanism during viral lytic replication. During viral latency, KSHV alters m⁶ A on genes that are implicated in cellular transformation and viral latency. Lastly, we discuss future studies that are important to further delineate the functions of m⁶ A in KSHV latent and lytic replication and KSHV-induced oncogenesis.

Lineage-specific STAT5 target gene activation in hematopoietic progenitor cells predicts the FLT3(+)-mediated leukemic phenotype

Mutations that activate FMS-like tyrosine kinase 3 (FLT3) are frequent occurrences in acute myeloid leukemia. Two distinct types of mutations have been described: internal duplication of the juxtamembranous domain (ITD) and point mutations of the tyrosine kinase domain (TKD). Although both mutations lead to constitutive FLT3 signaling, only FLT3-ITD strongly activates signal transducer and activator of transcription 5 (STAT5). In a murine transplantation model, FLT3-ITD induces a myeloproliferative neoplasm, whereas FLT3-TKD leads to a lymphoid malignancy with significantly longer latency. Here we report that the presence of STAT5 is critical for the development of a myeloproliferative disease by FLT3-ITD in mice. Deletion of Stat5 in FLT3-ITD-induced leukemogenesis leads not only to a significantly longer survival (82 vs 27 days) of the diseased mice, but also to an immunophenotype switch with expansion of the lymphoid cell compartment. Interestingly, we were able to show differential STAT5 activation in FLT3-ITD(+) myeloid and lymphoid murine progenitors. STAT5 target genes such as Oncostatin M were highly expressed in FLT3-ITD(+) myeloid but not in FLT3-ITD(+) lymphoid progenitor cells. Strikingly, FLT3-TKD expression in combination with Oncostatin M is sufficient to reverse the phenotype to a myeloproliferative disease in FLT3-TKD mice. Thus, lineage-specific STAT5 activation in hematopoietic progenitor cells predicts the FLT3(+)-mediated leukemic phenotype in mice.

Oncostatin M receptor is a novel therapeutic target in cervical squamous cell carcinoma

Cervical carcinoma is the second most common cause of cancer deaths in women worldwide. Treatments have not changed for decades and survival rates for advanced disease remain low. An exciting new molecular target for the treatment of cervical squamous cell carcinoma (SCC), and possibly for SCCs at other anatomical sites, is the oncostatin M receptor (OSMR). This cell surface cytokine receptor is commonly copy number gained and overexpressed in advanced cervical SCC, changes that are associated with significantly worse clinical outcomes. OSMR overexpression in cervical SCC cells results in enhanced responsiveness to the major ligand oncostatin M (OSM), which induces several pro-malignant effects, including a pro-angiogenic phenotype and increased cell migration and invasiveness. OSMR is a strong candidate for antibody-mediated inhibition, a strategy that has had a major impact on haematological malignancies and various solid tumours such as HER2-positive breast cancers.

PGP 9.5 neuronal marker may differentiate immunohistochemically HIV-related from Mediterranean and immunosuppression-associated Kaposi's sarcoma

Mediterranean Kaposi's sarcoma (MKS), HIV-related KS (HIV-KS) and immunosuppression-associated KS (IS-KS), caused by human herpes virus 8 (HHV-8), share similar histological features. The aim of this study was to investigate differences in epidermal nerve fibers (ENFs) between the three KS types and controls. Skin biopsies from 23 HIV-KS, 16 MKS, 28 IS-KS patients and 18 controls, age-gender matched, were immunostained with PGP 9.5; ENFs in upper epidermal layer (EL) and penetrating the basement membrane were measured. The mean number of nerve fibers penetrating ENFs was significantly lower in HIV-KS (p < 0.001) compared to all other groups. MKS and IS-KS had comparable ENFs but lower than controls (p < 0.00 1). In the upper EL all groups had comparable ENFs and lower than controls. In conclusion, HIV-KS can be distinguished histologically from other types, by counting ENFs. Moreover, KS is associated with decreased ENFs, which may be a histological reflection of nerve damage. This is even more pronounced in HIV-KS patients and could be explained by a neurotoxic action of HHV-8, HIV, and their co-existence.

Association of the oncostatin m receptor gene polymorphisms with papillary thyroid cancer in the korean population

Objectives

To investigate the association between papillary thyroid cancer (PTC) and single nucleotide polymorphisms (SNPs) of oncostatin M receptor (OSMR) in the Korean population.

Methods

Retrospective case-control study was done. Eighty-five patients with PTC and 287 controls were studied. One missense SNP (rs2278329, Asp553Asn) and one promoter SNP (rs2292016, -100 G/T) of the OSMR gene were genotyped by direct sequencing. Genetic data were analyzed using the SNPStats, Helixtree, and SNPAnalyzer Pro. PTC patients were dichotomized and compared with respect to the clinicopathologic characteristics.

Results

There was no association between genotypes and allele frequencies of OSMR SNPs (rs2278329 and rs2292016) and PTC susceptibility. SNP rs2278329 was significantly associated with tumor size (dominant model; P=0.028; odds ratio [OR], 2.71; 95% confidence interval [CI], 1.12 to 6.57). The A allele was higher in sizes large than 1 cm (32.5% vs. 16.7%; P=0.018; OR, 2.41; 95% CI, 1.17 to 4.98). Regarding the number of tumors, we found no significant association with genotype, however, the A allele was higher in patients with multifocaltiy (33.3% vs. 19.1%; P=0.040; OR, 2.12; 95% CI, 1.03 to 4.34).

Conclusion

The results suggest that OSMR polymorphism rs2278329 is associated with clinicopathologic characteristics of the tumor growth and multifocality development.

Blocking MAPK signaling downregulates CCL21 in lymphatic endothelial cells and impairs contact hypersensitivity responses

CCL21 expression by lymphatic endothelial cells (LECs) is essential for migration of CCR7+ immune cells from skin to regional lymph nodes (LNs). We investigated the importance of mitogen-activated protein kinase (MAPK) signaling in CCL21 expression by ECs in vitro and in vivo. Normal human dermal lymphatic microvascular ECs (HMVEC-dLy) stimulated in vitro with oncostatin M (OSM) expressed high amounts of CCL21 mRNA. CCL21 protein expression by HMVEC-dLy was also markedly increased by OSM compared with unstimulated cultures. Marked phosphorylation of MAPK 44/42 was detected in HMVEC-dLy stimulated by OSM. CCL21 expression by HMVEC-dLy was blocked by a JAK inhibitor 1, JAK3 inhibitor, and U0126 (a MAPK kinase inhibitor) in vitro, all of which blocked phosphorylation of MAPK 44/42. In addition, injection of U0126 into murine skin significantly decreased CCL21 mRNA and protein expression. Moreover, injection of U0126 before sensitization decreased migration of dendritic cells to draining LNs and decreased contact hypersensitivity responses. In summary, these results suggest that the MAPK pathway is important for CCL21 expression by LECs in vitro and in vivo. Blocking MAPK signaling within skin may offer a novel approach to treatment of inflammatory skin diseases.

Oncostatin M promotes STAT3 activation, VEGF production, and invasion in osteosarcoma cell lines

Background

We have previously demonstrated that both canine and human OSA cell lines, as well as 8 fresh canine OSA tumor samples, exhibit constitutive phosphorylation of STAT3, and that this correlates with enhanced expression of matrix metalloproteinase-2 (MMP2). While multiple signal transduction pathways can result in phosphorylation of STAT3, stimulation of the cytokine receptor gp130 through either IL-6 or Oncostatin M (OSM) is the most common mechanism through which STAT3 is activated. The purpose of this study was to evaluate the role of IL-6 and OSM stimulation on both canine and human OSA cell lines to begin to determine the role of these cytokines in the biology of OSA.

Methods

RT-PCR and Western blotting were used to interrogate the consequences of OSM and IL-6 stimulation of OSA cell lines. OSA cells were stimulated with OSM and/or hepatocyte growth factor (HGF) and the effects on MMP2 activity (gel zymography), proliferation (CyQUANT), invasion (Matrigel transwell assay), and VEGF production (Western blotting, ELISA) were assessed. The small molecule STAT3 inhibitor LLL3 was used to investigate the impact of STAT3 inhibition following OSM stimulation of OSA cells.

Results

Our data demonstrate that the OSM receptor (OSMR), but not IL-6 or its receptor, is expressed by all human and canine OSA cell lines and canine OSA tumor samples; additionally, OSM expression was noted in all tumor samples. Treatment of OSA cell lines with OSM induced phosphorylation of STAT3, Src, and JAK2. OSM stimulation also resulted in a dose dependent increase in MMP2 activity and VEGF expression that was markedly reduced following treatment with the small molecule STAT3 inhibitor LLL3. Lastly, OSM stimulation of OSA cell lines enhanced invasion through Matrigel, particularly in the presence of rhHGF. In contrast, both OSM and HGF stimulation of OSA cell lines did not alter their proliferative capacity.

Conclusions

These data indicate OSM stimulation of human and canine OSA cells induces STAT3 activation, thereby enhancing the expression/activation of MMP2 and VEGF, ultimately promoting invasive behavior and tumor angiogenesis. As such, OSM and its receptor may represent a novel target for therapeutic intervention in OSA.

Kaposi's sarcoma and its associated herpesvirus

Kaposi's sarcoma (KS) is the most common cancer in HIV-infected untreated individuals. Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 (HHV8)) is the infectious cause of this neoplasm. In this Review we describe the epidemiology of KS and KSHV, and the insights into the remarkable mechanisms through which KSHV can induce KS that have been gained in the past 16 years. KSHV latent transcripts, such as latency-associated nuclear antigen (LANA), viral cyclin, viral FLIP and viral-encoded microRNAs, drive cell proliferation and prevent apoptosis, whereas KSHV lytic proteins, such as viral G protein-coupled receptor, K1 and virally encoded cytokines (viral interleukin-6 and viral chemokines) further contribute to the unique angioproliferative and inflammatory KS lesions through a mechanism called paracrine neoplasia.

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.

Mice overexpressing murine oncostatin M (OSM) exhibit changes in hematopoietic and other organs that are distinct from those of mice overexpressing human OSM or bovine OSM

Oncostatin M (OSM) and leukemia inhibitory factor (LIF) belong to the interleukin-6 family of cytokines. The authors' previous in vitro work demonstrated that in mouse cells mouse OSM (mOSM) signals through a heterodimeric receptor complex incorporating the mOSM-specific receptor mOSMRbeta while human OSM (hOSM) and bovine OSM (bOSM) use the mouse LIF receptor mLIFRbeta rather than mOSMRbeta. These in vitro data suggest that prior studies in mouse systems with hOSM or bOSM (the usual molecules used in early studies) reflect LIF rather than OSM biology. The current work assessed whether or not this divergence in actions among these three OSMs also occurs in vivo in mouse models. Adult female (C57BL/6J x DBA/2J) F(1) mice were engineered to stably overexpress mOSM, hOSM, or bOSM by retrovirus-mediated gene transfer (n = 10 or more per group). After 4 weeks, molecular and hematologic profiles and anatomic phenotypes in multiple organs were assessed by standard techniques. Animals overexpressing either hOSM or bOSM had an identical phenotype resembling that associated with LIF activation, including significant hematologic abnormalities (anemia, neutrophilia, lymphopenia, eosinopenia, and thrombocytosis); weight loss; profound enlargement (lymph node, spleen) and/or structural reorganization (lymph node, spleen, thymus) of lymphoid organs; and severe osteosclerosis. In contrast, mice overexpressing mOSM did not develop hematologic changes, weight loss, or osteosclerosis and exhibited more modest and anatomically distinct restructuring of lymphoid organs. These data indicate that activities imputed to OSM and the mOSMRbeta signaling pathway using in vitro and in vivo mouse experimental systems are unique to mOSM.

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.

Kaposi sarcoma: a continuing conundrum

Kaposi sarcoma (KS) remains a challenge. Its classic or Mediterranean form tends to be benign. In transplant recipients it may be less so. As part of the AIDS pandemic, of which it was an original defining component, it may be life-threatening. It is due to human herpesvirus-8, which is necessary but not sufficient to produce the disease. KS has a low prevalence in the general population of the United States and United Kingdom, with an intermediate rate in Italy and Greece, and a high one in parts of Africa. In Italy, hot spots include its southern regions, the Po River Valley, and Sardinia, possibly related to a high density of blood-sucking insects. An important challenge is to treat KS patients without immunocompromising them. The potential of effective anti-herpes virus therapy and the use of sirolimus in transplantation recipients have added new opportunities for KS prevention.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be able to provide the most recent information about Kaposi sarcoma in the context in which it occurs. Its classic or Mediterranean form, its pattern in transplant recipients and others iatrogenically immunosuppressed, and its occurrence as a potentially life-threatening part of the AIDS pandemic will be stressed. Its etiology and transmission will be discussed in detail to facilitate understanding of Kaposi sarcoma and of human herpesvirus-8 infection in the general population of the United States and United Kingdom, in Italy and Greece, and in certain parts of Africa. Its therapy, including the concept of doing it without immunocompromising the patient, will be stressed. New opportunities for Kaposi sarcoma prevention will also be discussed.

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.

Oncostatin m maintains the hematopoietic microenvironment and retains hematopoietic progenitors in the bone marrow

Bone marrow (BM) functions as the primary hematopoietic tissue throughout adult life by providing a microenvironment for the proliferation, differentiation, and retention of hematopoietic stem cells and progenitors. We describe novel roles for oncostatin M (OSM) in the BM hematopoietic microenvironment. Hematopoietic progenitor activity in OSM-deficient mice was reduced in BM but elevated in the spleen and peripheral blood. The level of circulating granulocyte colony-stimulating factor (G-CSF) was increased, whereas that of stromal cell-derived factor 1 (SDF-1) was decreased in OSM-deficient mice. Moreover, the ability of OSM-deficient BM stromal cells to support hematopoiesis in vitro was significantly reduced. These results indicate that OSM plays a unique role in hematopoiesis by maintaining the proper microenvironment for BM hematopoiesis; it also retains hematopoietic progenitors in BM by regulating G-CSF and SDF-1 levels.

Molecular and Functional Characterization of a Soluble Form of Oncostatin M/Interleukin-31 Shared Receptor

Activation of the signaling transduction pathways mediated by oncostatin M (OSM) requires the binding of the cytokine to either type I OSM receptor (leukemia inhibitory factor receptor/gp130) or to type II OSM receptor (OSMR/gp130). In the present work we have developed an enzyme-linked immunosorbent assay detecting a soluble form of OSMR (sOSMR) secreted by glioblastoma, hepatoma, and melanoma tumor cell lines. sOSMR was also present in sera of healthy individuals, with increased levels in multiple myeloma. Molecular cloning of a corresponding cDNA was carried out, and it encoded for a 70-kDa protein consisting of a half cytokine binding domain containing the canonical WSXWS motif, an immunoglobulin-like domain, and the first half of a second cytokine binding domain with cysteines in fixed positions. Analysis of the soluble receptor distribution revealed a preferential expression in lung, liver, pancreas, and placenta. sOSMR was able to bind OSM and interleukin-31 when associated to soluble gp130 or soluble interleukin-31R, respectively, and to neutralize both cytokine properties. We have also shown that OSM could positively regulate the synthesis of its own soluble receptor in tumor cells.

Oncostatin M Enhances CCL21 Expression by Microvascular Endothelial Cells and Increases the Efficiency of Dendritic Cell Trafficking to Lymph Nodes

CCL21, a lymphatic endothelial cell (LEC)-derived chemokine, and its receptor CCR7 regulate dendritic cell (DC) trafficking to lymph nodes (LN), but it is unclear how CCL21 expression is regulated. Oncostatin M (OSM) is an IL-6-like cytokine synthesized by activated DC and other leukocytes. In vitro, OSM (but not TNF-alpha) stimulated CCL21 mRNA and protein expression by human dermal microvascular EC (DMEC) in an ERK1/2-dependent fashion. Conditioned medium from OSM-treated DMEC stimulated CCL21-dependent chemotaxis of mouse bone marrow-derived DC (BMDC). Cultured BMDC expressed OSM, which was increased with the addition of LPS. Topical application of the contact-sensitizing hapten, trinitrochlorobenzene, resulted in enhanced OSM expression in the skin, whereas cutaneous injection of TNF-alpha did not. Injection of OSM into the footpad increased CCL21 mRNA expression in the draining LN by approximately 10-fold and in mouse skin by approximately 4-fold without increasing CCR7 mRNA. In vitro, OSM increased the permeability of DMEC and lung microvascular EC monolayers to FITC-dextran beads, and, in vivo, it enhanced accumulation of Evans blue dye in draining LN by approximately 3-fold (p = 0.0291). Of note, OSM increased trafficking of BMDC injected in footpads to draining LN by 2-fold (p = 0.016). In summary, OSM up-regulates CCL21 expression in skin and draining regional LN. We propose that OSM is a regulator of CCL21 expression and endothelial permeability in skin, contributing to efficient migration of DC to regional LN.

Divergent effects of oncostatin M on astroglioma cells: influence on cell proliferation, invasion, and expression of matrix metalloproteinases

Oncostatin M (OSM), a cytokine of the interleukin-6 (IL-6) family, can either promote or inhibit cell growth in various normal and tumor cells. We addressed the effects of exogenous OSM on the proliferation and invasion of human astroglioma cells. In addition, we investigated one of the possible mechanisms involved: modulation of matrix metalloproteinase (MMP) expression and enzymatic activity. We found that OSM inhibited the proliferation of two human astroglioma cell lines (CH235-MG and U87-MG), and that this effect was not due to apoptosis. The inhibitory effect of OSM on proliferation was mediated through the gp130/OSMRbeta receptor complex. To extend these findings, we analyzed the effects of OSM on primary tumor cells from glioblastoma patients. OSM suppressed the proliferation of primary glioblastoma cells, but not that of normal astrocytes. Interestingly, OSM did not suppress astroglioma cell invasion. This may be due to the differential regulation of MMPs by OSM. We found that OSM inhibited the constitutive expression of MMP-2, while MMP-9 expression was enhanced in astroglioma cell lines. We conclude that OSM inhibits proliferation of human astroglioma cells and primary glioblastoma cells via the gp130/OSMRbeta receptor complex. However, OSM does not affect the invasive capacity of the astroglioma cells, which may be due to the divergent effects of OSM on MMP-2 and MMP-9 expression. Collectively, these findings suggest a complex role for OSM in astroglioma biology.

Oncostatin M induces proliferation of human adipose tissue-derived mesenchymal stem cells

Interleukin-6 (IL-6) subfamily of cytokines, including oncostatin M (OSM), leukemia inhibitory factor (LIF), and IL-6, has been implicated in a variety of physiological responses, such as cell growth, differentiation, and inflammation. In the present study, we demonstrated that both OSM and LIF stimulated the proliferation of human adipose tissue-derived mesenchymal stem cells (hATSCs), however, IL-6 had no effect on cell proliferation. OSM treatment induced phosphorylation of ERK, and pretreatment with U0126, a MEK inhibitor, prevented the OSM-stimulated proliferation of hATSCs, suggesting that the MEK/ERK pathway is involved in the OSM-induced proliferation. Treatment with OSM also induced phosphorylation of JAK2 and JAK3, and pretreatment of the cells with WHI-P131, a JAK3 inhibitor, but not with AG490, a JAK2 inhibitor, attenuated the OSM-induced proliferation of hATSCs. Furthermore, OSM treatment elicited phosphorylation of STAT1 and STAT3, and pretreatment with WHI-P131 specifically prevented the OSM-induced phosphorylation of STAT1, without affecting the OSM-induced phosphorylation of ERK and STAT3. These results suggest that two separate signaling pathways, such as MEK/ERK and JAK3/STAT1, are independently involved in the OSM-stimulated proliferation of hATSCs.

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.

Oncostatin M-induced activation of stress-activated MAP kinases depends on tyrosine 861 in the OSM receptor and requires Jak1 but not Src kinases

We have investigated the molecular mechanisms involved in the activation process of the stress-activated protein kinases (SAPK) p38 and JNK in response to the interleukin-6-type cytokine oncostatin M (OSM). Interestingly, activation of p38 and JNK originates from tyrosine residue 861 in the OSMR; the same tyrosine residue which we identified before to be involved in the activation of the mitogen-activated kinases Erk1/2 [Hermanns, H. M., Radtke, S., Schaper, F., Heinrich, P. C., and Behrmann, I. (2000) J. Biol. Chem. 275, 40742-40748]. Therefore, activation of members belonging to all three MAPK families is mediated by one tyrosine motif in the cytoplasmic region of the human OSMR. Concomitantly, point mutation of this residue abrogates the phosphorylation of these kinases. The Janus kinase Jak1 is absolutely essential for the activation of p38 in response to OSM, while Src kinase family members appear to be generally dispensable. Finally, we demonstrate that mutation of tyrosine 861 abrogates OSMR-mediated cell proliferation and identify Erk1/2 as mainly responsible for the proliferative effect. Erk1/2 activation is negatively influenced by p38 activation and inhibition of p38 significantly prolongs the half-life of OSM-induced Egr-1.

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.

Comparative study of regulation of RTA-responsive genes in Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8

Replication and transcription activator (RTA) (also referred to as ORF50), an immediate-early gene product of Kaposi's sarcoma-associated herpesvirus (KSHV)/(human herpesvirus 8), plays a critical role in balancing the viral life cycle between latency and lytic replication. RTA has been shown to act as a strong transcription activator for several downstream genes of KSHV. Direct binding of RTA to DNA is thought to be one of the important mechanisms for transactivation of target genes, while indirect mechanisms are also implicated in RTA transactivation of certain selected genes. This study demonstrated direct binding of the DNA-binding domain of RTA (Rdbd) to a Kaposin (Kpsn) promoter sequence, which is highly homologous to the RTA-responsive element (RRE) of the PAN promoter. We undertook a comparative study of the RREs of PAN RNA, ORF57, vIL-6, and Kpsn to understand how RTA regulates gene expression during lytic replication. Comparing RNA abundance and transcription initiation rates of these RTA target genes in virus-infected cells suggested that the transcription initiation rate of the promoters is a major determinant of viral gene expression, rather than stability of the transcripts. RTA-mediated transactivation of reporters containing each RRE showed that their promoter strengths in a transient-transfection system were comparable to their transcription rates during reactivation. Moreover, our electrophoretic mobility shift assays of each RRE demonstrated that the highly purified Rdbd protein directly bound to the RREs. Based on these results, we conclude that direct binding of RTA to these target sequences contributes to their gene expression to various extents during the lytic life cycle of KSHV.

Molecular genetics of Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8) epidemiology and pathogenesis

Kaposi's sarcoma had been recognized as unique human cancer for a century before it manifested as an AIDS-defining illness with a suspected infectious etiology. The discovery of Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8, in 1994 by using representational difference analysis, a subtractive method previously employed for cloning differences in human genomic DNA, was a fitting harbinger for the powerful bioinformatic approaches since employed to understand its pathogenesis in KS. Indeed, the discovery of KSHV was rapidly followed by publication of its complete sequence, which revealed that the virus had coopted a wide armamentarium of human genes; in the short time since then, the functions of many of these viral gene variants in cell growth control, signaling apoptosis, angiogenesis, and immunomodulation have been characterized. This critical literature review explores the pathogenic potential of these genes within the framework of current knowledge of the basic herpesvirology of KSHV, including the relationships between viral genotypic variation and the four clinicoepidemiologic forms of Kaposi's sarcoma, current viral detection methods and their utility, primary infection by KSHV, tissue culture and animal models of latent- and lytic-cycle gene expression and pathogenesis, and viral reactivation from latency. Recent advances in models of de novo endothelial infection, microarray analyses of the host response to infection, receptor identification, and cloning of full-length, infectious KSHV genomic DNA promise to reveal key molecular mechanisms of the candidate pathogeneic genes when expressed in the context of viral infection.

Update on Kaposi's sarcoma and other HHV8 associated diseases. Part 2: pathogenesis, Castleman's disease, and pleural effusion lymphoma

The pathogenesis of Kaposi's sarcoma (KS) is better understood since the identification of the novel human herpesvirus 8 (HHV8), which can be found in all forms of KS. Viral oncogenesis and cytokine-induced growth, as well as some states of immunocompromise, contribute to its development. Several virally encoded genes--eg, bcl-2, interleukin 6, cyclin D, G-protein-coupled receptor, and interferon regulatory factor--provide key functions on cellular proliferation and survival. Growth promotion of KS is further stimulated by various proinflammatory cytokines and growth factors such as tumour necrosis factor a, interleukin 6, basic fibroblast growth factor, and vascular endothelial growth factor, resulting in a hyperplastic polyclonal lesion with predominant spindle cells derived from lymphoid endothelia. HHV8 has recently been discovered to escape HLA-class-I-restricted antigen presentation to cytotoxic T lymphocytes by increasing endocytosis of MHC class I chains from the cell surface, thus enabling latent infection and immune escape in primary and chronic infection. Multicentric Castleman's disease is a rare lymphoproliferative disorder of the plasma cell type, which has been reported in both HIV-seropositive and HIV-seronegative patients, and which frequently contains HHV8 DNA. Pleural effusion lymphoma, or body-cavity-based lymphoma, belongs to the group of non-Hodgkin B-cell lymphomas characterised by pleural, pericardial, or peritoneal lymphomatous effusions in the absence of a solid tumour mass. Pleural effusion lymphoma has an intermediate immunophenotype lacking B or T lymphocyte antigens and also belongs to the diseases associated with HHV8.

Human herpesvirus 8-derived viral IL-6 induces PTX3 expression in Kaposi's sarcoma cells

OBJECTIVE

To analyse if human herpesvirus 8 (HHV8)-derived viral interleukin-6 (vIL-6) has the capacity to activate Kaposi's sarcoma (KS) cells to elicit a local acute-phase response.

DESIGN

Proinflammatory activation of KS cells was compared using vIL-6, human IL-6, as well as the complex of human IL-6 with the soluble IL-6 receptor, and expression of the novel acute-phase protein pentraxin-3 (PTX3) was analysed.

METHODS

We established primary KS cell cultures from patients with AIDS-associated and classical KS and expressed recombinant HHV8-derived vIL-6 in COS-7 cells. Expression of PTX3 by vIL-6-stimulated KS cell cultures was analysed by quantitative real-time reverse transcriptase-polymerase chain reaction. Mitogenic effects of vIL-6 on the KS cells of distinct aetiology were compared by [3H]thymidine incorporation.

RESULTS

We show that vIL-6 induced a marked and sustained expression of the novel acute-phase protein PTX3 in human primary KS cell cultures. vIL-6 directly activated KS cells, which uniquely expressed gp130, the signal-transducing subunit of the IL-6 receptor, but were negative for the IL-6-binding unit (IL-6R). In contrast, human IL-6 did not stimulate KS cells in the absence of the full IL-6R. Expression of PTX3 messenger RNA increased by more than 25-fold in vIL-6-stimulated KS cells after 24 h. Particularly after extended incubation with the virokine, vIL-6 mediated a pronounced mitogenic effect on KS cells.

CONCLUSION

The induction of an extrahepatic acute-phase response by vIL-6-activated KS cells may contribute to local tissue damage and the attraction of inflammatory cells, and add to a more aggressive phenotype.

Characterization of interactions between RTA and the promoter of polyadenylated nuclear RNA in Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8

RTA (replication and transcription activator; also referred to as ORF50, Lyta, and ART), an immediate-early gene product of Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8, disrupts latency and drives lytic replication. RTA activates the expression of polyadenylated nuclear (PAN) RNA (also known as T1.1 or nut-1) of KSHV. This novel noncoding PAN RNA is the most abundant lytic transcript of KSHV; therefore, studying PAN RNA expression serves as a model system for understanding how RTA transactivates target genes during lytic replication. The RTA-responsive element of the PAN promoter (pPAN RRE) was previously identified, and our data suggested direct binding of full-length RTA to the pPAN RRE. Here, we present a detailed analysis of specific interactions between RTA and the PAN promoter. We expressed and purified the DNA-binding domain of RTA (Rdbd) to near homogeneity and measured its affinity for the pPAN RRE. In electrophoretic mobility shift assays (EMSAs), the dissociation constant (K(d)) of Rdbd on the pPAN RRE was determined to be approximately 8 x 10(-9) M, suggesting a strong interaction between RTA and DNA. The specificity of RTA binding to the PAN promoter was confirmed with supershift assays. The Rdbd binding sequences on the PAN promoter were mapped within a 16-bp region of the pPAN RRE by methylation interference assays. However, the minimal DNA sequence for Rdbd binding requires an additional 7 bp on both sides of the area mapped by interference assays, suggesting that non-sequence-specific as well as sequence-specific interactions between RTA and DNA contribute to high-affinity binding. To better understand the molecular interactions between RTA and the PAN promoter, an extensive mutagenesis study on the pPAN RRE was carried out by using EMSAs and reporter assays. These analyses revealed base pairs critical for both Rdbd binding in vitro and RTA transactivation in vivo of the PAN promoter. The results from methylation interference, deletion analysis, and mutagenesis using EMSAs and reporter assays were closely correlated and support the hypothesis that RTA activates PAN RNA expression through direct binding to DNA.

Novel role of Janus kinase 1 in the regulation of oncostatin M receptor surface expression

The oncostatin M receptor (OSMR) is part of a heterodimeric receptor complex that mediates signal transduction of the pleiotropic cytokine OSM via a signaling pathway involving Janus kinases (Jaks) and transcription factors of the signal transducers and activators of transcription (STAT) family. Upon heterologous expression of the OSMR in several cell lines, we observed that its surface expression was significantly enhanced by coexpression of the Janus kinases Jak1, Jak2, and Tyk2 but not Jak3. Chimeric receptors consisting of the extracellular region of the interleukin-5 receptor beta chain and the transmembrane and intracellular part of the OSMR were similarly up-regulated on the plasma membrane when Jak1 was coexpressed. The overall expression level of these constructs did not change significantly, but Jak1 coexpression increased the amount of endoglycosidase H-resistant, fully processed OSMR chimeras. Using mutated receptor and Jak1 constructs, we were able to demonstrate that association of Jak1 with the membrane proximal region of the receptor, but not its kinase activity, is necessary for this effect. Moreover, deletion of the OSMR box1/2 region also resulted in an improved surface expression indicating that this region may contain a signal preventing efficient receptor surface expression in the absence of associated Jaks. Finally we demonstrate that in Jak1-deficient cells, the endogenous OSMR is significantly down-regulated, an effect that can be reversed by transient expression of Jak1 in these cells.

Coexpression of oncostatin M and its receptors and evidence for STAT3 activation in human ovarian carcinomas

The expression of oncostatin M and leukemia inhibitory factor (LIF), JAK-STAT activators and members of the interleukin-6 family of cytokines, were examined in a series of primary ovarian carcinomas using immunohistochemistry. The malignant epithelial cells of all 29 ovarian carcinomas examined expressed oncostatin M; none expressed LIF. Oncostatin M can activate two related receptors, one consisting of a low-affinity LIF receptor subunit, LIFR beta, which forms a heterocomplex with the gp130 signal transducing protein and can recognize both oncostatin M and LIF, and a second heterocomplex consisting of a subunit that specifically recognizes oncostatin M, OSMR beta, and the gp130 protein. By immunohistochemistry, 25 of 25 ovarian carcinomas examined expressed the LIFR beta subunit in the malignant epithelial cells (all samples express gp130), and two-thirds the ovarian carcinomas studied expressed OSMR beta mRNA as determined by RT-PCR. Thus oncostatin M and its receptors are commonly coexpressed in malignant ovarian epithelial cells, and represent a potential autocrine loop in this tumor type. STAT3, of one the signaling proteins downstream of the oncostatin M/LIF receptors, was found in its phosphorylated, activated form (phosphotyrosine 705 STAT3) in the malignant epithelial cells of 17 of 23 ovarian carcinomas examined (74%) as determined by immunohistochemistry; this suggests that this protein is constitutively activated in most ovarian carcinomas, as it is in many other human malignancies. Recombinant human Oncostatin M (rhOSM) can induce the transient tyrosine 705 phosphorylation of STAT3 in serum-starved LIFR beta/OSMR beta expressing ovarian carcinoma cell lines, but does not alter cell growth and effects only a modest increase in the apoptotic rate in these cultured cells. Oncostatin M and its receptors may be part of a network of cytokine systems within ovarian carcinomas that may act to maintain STAT3 in its activated form, a phenomenon associated with the malignant phenotype.

Multiple sclerosis and Kaposi's sarcoma--chronic diseases associated with new human herpesviruses?

Two diseases that for many years have been suspected to be of viral origin are multiple sclerosis (MS) and Kaposi's sarcoma (KS). With the use of a new technique called representational difference analysis both these diseases have recently been associated with new lymphotropic herpesviruses, i.e. human herpesviruses (HHV) 6 and 8. HHV-6 is a ubiquitous virus and the etiological agent of exanthema subitum. Viral neuroinvasion occurs frequently in primary HHV-6 infection, and meningitis, encephalitis and demyelination have been described as rare complications. A relation with MS has been suggested for HHV-6, as the virus has been detected in MS plaques in the brain. Data from different studies are, however, conflicting and a definitive role for HHV-6 in MS pathogenesis has not been established. HHV-8 is believed to be the causative agent of KS, and is also associated with some rare hematological malignancies. The viral genome contains several potential oncogenes that are believed to have been picked up from the human genome during evolution. The role of HHV-8 in healthy, immunocompetent individuals is however uncertain. In conclusion, the full spectrum of human diseases associated with these new viruses is not yet understood, and rapid developments in molecular biology will continue to shed new light on the interactions between herpesviruses and their hosts.

Effects of oncostatin M on human cerebral endothelial cells and expression in inflammatory brain lesions

Oncostatin M (OSM) is a member of the interleukin (IL)-6 cytokine family and modulates inflammatory responses. Here we investigated the role of OSM as an immunoregulatory factor for human cerebral endothelial cells (HCEC). Using RT-PCR we detected transcripts of the receptor components involved in OSM signaling, gp130, OSM receptor (OSMR)-beta, and leukemia inhibitory factor receptor (LIFR), in HCEC. A parallel FACS analysis revealed surface expression of gp130 and OSMR-beta, but not of LIFR on these cells. Functionally, OSM upregulated intercellular adhesion molecule-1, but did not induce vascular cell adhesion molecule-1 in HCEC. Further, OSM upregulated IL-6 and monocyte chemoattractant protein (MCP)-1, whereas IL-8 was unaffected. Combined application of tumor necrosis factor (TNF)-alpha and OSM synergistically enhanced IL-6 and MCP-1 production, but downregulated TNF-alpha-induced IL-8. As OSM regulated molecules relevant in inflammatory brain diseases, we investigated its expression in normal and pathological human brains. OSM was detected by immunohistochemistry in brains from multiple sclerosis patients in microglia, reactive astrocytes, and infiltrating leukocytes, whereas in normal brains and noninflammatory neurological diseases. immunoreactivity was absent from the parenchyma. These data suggest that immunoregulatory functions in human cerebral endothelial cells may be a mechanism by which OSM participates in the pathophysiology of inflammatory brain disease.

Menstrual cycle-specific inhibition of endometrial stromal cell proliferation by oncostatin M

We have investigated the possible roles of oncostatin M (OSM), which is a member of the interleukin-6 family of cytokines, in endometrial and endometriotic stromal cell growth. Endometrial and endometriotic stromal cells were collected from the uterus or ovarian chocolate cysts. We observed the expression of mRNA transcripts for OSM, OSM receptor subunit beta, leukaemia inhibitory factor receptor subunit (LIFR), and glycoprotein 130 in endometrial and endometriotic stromal cells. We also examined the effects of OSM (0-50 ng/ml) and LIF (0-10 ng/ml) on endometrial and endometriotic stromal cell proliferation and evaluated the effects of OSM on endometrial stromal cell differentiation. The presence of 10-50 ng/ml OSM significantly suppressed endometrial stromal cell growth in secretory phase tissue but not in proliferative phase tissue. In contrast, stromal cells in endometriotic tissues were resistant to the inhibitory effects of OSM. Addition of LIF did not influence the growth of endometrial stromal cells. We also showed that 10 ng/ml OSM stimulated markers of differentiation causing increased prolactin secretion and cyclooxygenase-2 gene expression in endometrial stromal cells from the secretory phase. These results suggest that OSM may play a pivotal role in regulating the growth and differentiation of endometrial cells. Endometriotic cells may behave differently from normal endometrial cells in terms of the inhibitory response to OSM.

Induction of interleukin-6 and oncostatin M by radiation in Kaposi's sarcoma cell lines

PURPOSE

To define the in vitro radiosensitivity of Kaposi's sarcoma (KS) and to explore the mechanism of its extreme clinical radiosensitivity.

METHODS AND MATERIALS

The radiation survivals of the three KS cell cultures (KSY-1, KS-JD, KS6-3E) were determined by clonogenic assay and MTT assay. Supernatants from irradiated cells were collected at different time points for measurement of the interleukin 6 (IL-6), oncostatin M (OSM), and basic fibroblast growth factor (bFGF) by ELISA. Changes in the mRNA expression of these cytokines were examined by reverse transcription polymerase chain reaction and Southern blot hybridization. Fresh KS cells were preincubated with the irradiated supernatant before irradiation, and the change in survivals were assessed.

RESULTS

The mean SF-2 (survival fraction after 2 Gy) for KS was 0.43. Preincubation with the irradiated supernatant reduced the SF-2 significantly from 0.43 to 0.33 (p < 0.05). Treatment with irradiated supernatant alone was not cytotoxic to the cells. Radiation induced IL-6 and OSM production by KS cells at the transcription level. A single dose of 2 Gy increased IL-6 and OSM mRNA expression of the KS Y-1 cells. This corresponded to an increase in the IL-6 and OSM levels in the culture medium. There was no significant change in the level of bFGF. Preincubation with recombinant human IL-6 or OSM sensitized KS in a dose dependent manner.

CONCLUSION

The low SF-2 value for these KS cell lines correlates with the clinical radiosensitivity of KS. The high radiosensitivity may be due to radiation induction of cytokines such as IL-6 and OSM, which are radiosensitizers for KS cells.

Transcription activation of polyadenylated nuclear rna by rta in human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus

Human herpesvirus 8 (HHV-8) (also known as Kaposi's sarcoma-associated herpesvirus) encodes a novel noncoding polyadenylated nuclear (PAN) RNA (also known as T1.1 or nut-1) during the early phase of lytic replication. PAN RNA is the most abundant transcript of HHV-8, comprising 80% of total poly(A)-selected transcripts in HHV-8-infected cells during lytic replication. We directly measured the abundance of PAN RNA by visualizing 1.1- to 1.2- kb PAN RNA in an ethidium bromide-stained gel from poly(A)-selected RNA. We further pursued the mechanisms by which PAN RNA expression is induced to such high levels. rta, an immediate-early gene of HHV-8, is a transactivator that is sufficient and necessary to activate lytic gene expression in latently infected cells. Ectopic expression of Rta was previously shown to induce PAN RNA expression from the endogenous viral genome and activate the PAN promoter in a reporter system. Here, we have identified the Rta-responsive element (RRE) in the PAN promoter. Deletion analysis revealed that the RRE is present in a region between nucleotides -69 and -38 of the PAN promoter. A promoter construct containing the 69 nucleotides upstream of the transcription start site of the PAN promoter was activated by Rta in the absence or presence of the HHV-8 genome. Rta activated the PAN promoter up to 7,000-fold in 293T cells and 2,000-fold in B cells. Electrophoretic mobility shift assays demonstrated that Rta formed a highly stable complex with the RRE of the PAN promoter. Our study suggests that Rta can induce PAN RNA expression by direct binding of Rta to the RRE of the PAN promoter. This study has highlighted an important mechanism controlling PAN RNA expression and also provides a model system for investigating how Rta transactivates gene expression during lytic replication.

Oncostatin M promotes biphasic tissue factor expression in smooth muscle cells: evidence for Erk-1/2 activation

Tissue factor (TF), a transmembrane glycoprotein, initiates the extrinsic coagulation cascade. TF is known to play a major role in mediating thrombosis and thrombotic episodes associated with the progression of atherosclerosis. Macrophages at inflammatory sites, such as atherosclerotic lesions, release numerous cytokines that are capable of modulating TF expression. This study examined the role of oncostatin M (OSM), a macrophage/ T-lymphocyte-restricted cytokine, in the expression of TF in vascular smooth muscle cells (SMCs). It is reported here that OSM stimulated a biphasic and sustained pattern of TF messenger RNA (mRNA). The effect of OSM on TF mRNA expression was regulated at the transcriptional level as determined by nuclear run-offs and transient transfection of a TF promoter-reporter gene construct. OSM-induced TF expression was regulated primarily by the transcription factor NF-kappaB. Activation of NF-kappaB by OSM did not require IkappaB-alpha degradation. Inhibition of MEK activity by U0126 prevented OSM-induced TF expression by suppressing NF-kappaB DNA binding activity as determined by gel-shift analysis. Further, inhibition of Erk-1/2 protein by antisense treatment resulted in suppression of TF mRNA expression, indicating a role for Erk-1/2 in modulating NF-kappaB DNA binding activity. These studies suggest that the induced expression of TF by OSM is primarily through the activation of NF-kappaB and that activation of NF-kappaB is regulated in part by the MEK/Erk-1/2 signal transduction pathway. This study indicates that OSM may play a key role in promoting TF expression in SMCs within atherosclerotic lesions.