Genomic Landscape Survey Identifies SRSF1 as a Key Oncodriver in Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is an aggressive disease with poor survival. A few sequencing studies performed on limited number of samples have revealed potential disease-driving genes in SCLC, however, much still remains unknown, particularly in the Asian patient population. Here we conducted whole exome sequencing (WES) and transcriptomic sequencing of primary tumors from 99 Chinese SCLC patients. Dysregulation of tumor suppressor genes TP53 and RB1 was observed in 82% and 62% of SCLC patients, respectively, and more than half of the SCLC patients (62%) harbored TP53 and RB1 mutation and/or copy number loss. Additionally, Serine/Arginine Splicing Factor 1 (SRSF1) DNA copy number gain and mRNA over-expression was strongly associated with poor survival using both discovery and validation patient cohorts. Functional studies in vitro and in vivo demonstrate that SRSF1 is important for tumorigenicity of SCLC and may play a key role in DNA repair and chemo-sensitivity. These results strongly support SRSF1 as a prognostic biomarker in SCLC and provide a rationale for personalized therapy in SCLC.

A Potent HER3 Monoclonal Antibody That Blocks Both Ligand-Dependent and -Independent Activities: Differential Impacts of PTEN Status on Tumor Response.

HER3/ERBB3 is a kinase-deficient member of the EGFR family receptor tyrosine kinases (RTK) that is broadly expressed and activated in human cancers. HER3 is a compelling cancer target due to its important role in activation of the oncogenic PI3K/AKT pathway. It has also been demonstrated to confer tumor resistance to a variety of cancer therapies, especially targeted drugs against EGFR and HER2. HER3 can be activated by its ligand (heregulin/HRG), which induces HER3 heterodimerization with EGFR, HER2, or other RTKs. Alternatively, HER3 can be activated in a ligand-independent manner through heterodimerization with HER2 in HER2-amplified cells. We developed a fully human mAb against HER3 (KTN3379) that efficiently suppressed HER3 activity in both ligand-dependent and independent settings. Correspondingly, KTN3379 inhibited tumor growth in divergent tumor models driven by either ligand-dependent or independent mechanisms in vitro and in vivo Most intriguingly, while investigating the mechanistic underpinnings of tumor response to KTN3379, we discovered an interesting dichotomy in that PTEN loss, a frequently occurring oncogenic lesion in a broad range of cancer types, substantially blunted the tumor response in HER2-amplified cancer, but not in the ligand-driven cancer. To our knowledge, this represents the first study ascertaining the impact of PTEN loss on the antitumor efficacy of a HER3 mAb. KTN3379 is currently undergoing a phase Ib clinical trial in patients with advanced solid tumors. Our current study may help us optimize patient selection schemes for KTN3379 to maximize its clinical benefits. Mol Cancer Ther; 15(4); 689-701. ©2016 AACR.

In Vivo Therapeutic Success of MicroRNA-155 Antagomir in a Mouse Model of Lupus Alveolar Hemorrhage.

OBJECTIVE: Diffuse alveolar hemorrhage (DAH) is a rare but life-threatening complication of systemic lupus erythematosus (SLE). Pristane-treated B6 mice develop severe DAH within 2 weeks of treatment. MicroRNA-155 (miR-155) is a pleiotropic microRNA that plays a crucial role in the regulation of immune responses. Recent studies have revealed a pathogenic role of miR-155 in various autoimmune disorders. The purpose of this study was to examine the role of miR-155 in the development of DAH in pristane-induced lupus using miR-155-knockout (miR-155(-/-)) mice and miR-155 antagomir to silence miR-155. METHODS: DAH was induced by an intraperitoneal injection of 0.5 ml of pristane. MicroRNA-155 antagomir was administered intravenously to silence miR-155 expression. Lung tissues were collected for RNA extraction and were embedded in paraffin for sectioning. Gene expression profiling data were analyzed using Ingenuity Pathway Analysis. Real-time quantitative polymerase chain reaction analysis was used for single-gene validation. Luciferase reporter assay and argonaute 2 immunoprecipitation were performed for target validation. RESULTS: MicroRNA-155 expression was significantly increased during the development of DAH. Disease progression was reduced in miR-155(-/-) mice as well as by in vivo silencing of miR-155 using a miR-155 antagomir. MicroRNA-155 silencing dampened pristane-induced ectopic activation of multiple inflammatory pathways and reduced the expression of proinflammatory cytokines. Several negative regulators of NF-κB signaling were inhibited by pristane and were reactivated in miR-155(-/-) mice. In particular, the antiinflammatory factor peroxisome proliferator-activated receptor α was identified as a direct target of miR-155. CONCLUSION: MicroRNA-155 promotes pristane-induced lung inflammation. It contributes to ectopic activation of NF-κB signaling pathways by targeting multiple negative regulators. MicroRNA-155 antagomir may be a promising therapeutic strategy for treating acute lung inflammation in lupus.

Identification of Cyclin-Dependent Kinase 1 as a Novel Regulator of Type I Interferon Signaling in Systemic Lupus Erythematosus.

OBJECTIVE: Type I interferon (IFN) signaling is regarded as a central pathogenic pathway in systemic lupus erythematosus (SLE). Specific inhibition of this pathway is a core area for the development of new therapies for SLE. This study was undertaken to clarify the pathogenic mechanism involved and to identify new therapeutic targets, using a high-throughput screening platform to determine novel regulators that contribute to the overactivation of the type I IFN signaling pathway in SLE. METHODS: A high-throughput IFN-stimulated response element (ISRE)-luciferase assay was used to screen for candidate genes that regulate the IFN signaling pathway. Western blotting was used to confirm the regulatory function of CDK1. SYBR Green quantitative reverse transcriptase-polymerase chain reaction was used to detect the expression of individual IFN-stimulated genes (ISGs). The differential expression of CDK1 and ISGs in SLE patients and healthy controls was analyzed using RNA sequencing data and a microarray. RESULTS: The high-throughput ISRE-luciferase assay revealed that CDK1 enhanced type I IFN signaling. Consistent with this finding, CDK1 promoted the type I IFN-induced phosphorylation of STAT-1 and the up-regulated expression of ISGs. CDK1 expression was elevated in peripheral blood mononuclear cells (PBMCs) and kidney biopsy specimens from SLE patients and correlated positively with their IFN scores. A CDK1 inhibitor reduced the expression of ISGs in PBMCs from SLE patients and in renal cells from mice with lupus. CONCLUSION: Our findings indicate that CDK1 is a positive regulator of the IFN signaling pathway. The overexpression of CDK1 might contribute to the abnormally amplified type I IFN signaling in SLE, and the inhibition of CDK1 could be used to down-regulate type I IFN signaling in SLE.

Type I Interferon Inhibition of MicroRNA-146a Maturation Through Up-Regulation of Monocyte Chemotactic Protein-Induced Protein 1 in Systemic Lupus Erythematosus.

OBJECTIVE: Systemic lupus erythematosus (SLE) is characterized by the uncontrolled production of inflammatory cytokines, among which type I interferon (IFN) is recognized as a crucial pathogenic factor. The expression of microRNA-146a (miR-146a) is reduced in the white blood cells of SLE patients and accounts for their overactivated inflammatory responses. However, the mechanism of the reduction of miR-146a is still not fully understood. This study was undertaken to test whether the key pathogenic cytokine, type I IFN, is responsible for the dysregulation of miR-146a in SLE. METHODS: Gene and protein expression was measured in all cells by reverse transcription-quantitative polymerase chain reaction, Northern blotting, or Western blotting. In THP-1 cells, expression of monocyte chemotactic protein-induced protein 1 (MCPIP-1) was knocked down with a lentivirus encoding a short hairpin RNA targeting MCPIP1. The cells were pretreated with type I IFN and assessed for gene expression levels of miR-146a. White blood cells from patients with SLE were analyzed for the expression of the IFN-inducible genes MCPIP1 and miR-146a, and the gene expression data were compared for correlation. RESULTS: Pretreatment of THP-1 cells with type I IFN attenuated the induction of miR-146a posttranscriptionally, by down-regulating the expression of pre-miR-146a but not pri-miR-146a or its original unspliced transcript. Expression of MCPIP-1, which was enhanced by type I IFN, was found to be responsible for the inhibition of miR-146a. In white blood cells from patients with SLE, MCPIP1 expression was elevated, and its expression correlated positively with the IFN score and negatively with the miR-146a transcript level. CONCLUSION: Type I IFN inhibits the maturation of miR-146a through the up-regulation of MCPIP-1, and thus contributes to the uncontrolled inflammation and excessive inflammatory gene expression in SLE.

MiR-125a targets effector programs to stabilize Treg-mediated immune homeostasis.

Although different autoimmune diseases show discrete clinical features, there are common molecular pathways intimately involved. Here we show that miR-125a is downregulated in peripheral CD4(+) T cells of human autoimmune diseases including systemic lupus erythematosus and Crohn's disease, and relevant autoimmune mouse models. miR-125a stabilizes both the commitment and immunoregulatory capacity of Treg cells. In miR-125a-deficient mice, the balance appears to shift from immune suppression to inflammation, and results in more severe pathogenesis of colitis and experimental autoimmune encephalomyelitis (EAE). The genome-wide target analysis reveals that miR-125a suppresses several effector T-cell factors including Stat3, Ifng and Il13. Using a chemically synthesized miR-125a analogue, we show potential to re-programme the immune homeostasis in EAE models. These findings point to miR-125a as a critical factor that controls autoimmune diseases by stabilizing Treg-mediated immune homeostasis.

Inhibition of myogenic microRNAs 1, 133, and 206 by inflammatory cytokines links inflammation and muscle degeneration in adult inflammatory myopathies.

OBJECTIVE: The molecular basis of inflammatory myopathies such as dermatomyositis (DM), polymyositis, and inclusion body myositis, which share the characteristics of chronic muscle inflammation and skeletal muscle wasting, are poorly understood. As such, effective targeted treatments for these diseases are lacking, resulting in critical unmet medical needs for these devastating diseases. The purpose of this study was to identify possible new targets for drug development by exploring the mechanism by which inflammation may play a role in the pathology of the inflammatory myopathies. METHODS: We compared expression levels of inflammatory cytokines and microRNAs (miRNAs) between muscle biopsy samples from patients with inflammatory myopathies and those from donors without myositis. In vitro human and mouse model systems were then used to characterize the role of these cytokines and microRNAs on myoblast-to-myocyte differentiation. RESULTS: We observed increased expression of inflammatory cytokines, including tumor necrosis factor α (TNFα), interferon-α (IFNα), IFNß, and interleukin-1ß, in different subtypes of inflammatory myopathies. We observed decreased expression of microRNA-1 (miR-1), miR-133a, and miR-133b in all of the inflammatory myopathy subtypes we evaluated, as well as decreased expression of miR-206 in DM; these miRNAs are essential for adult skeletal muscle differentiation and maintenance. TNFα was significantly inversely correlated with decreased myogenic miRNA expression in the inflammatory myopathy subtypes. In mechanistic studies, TNFα inhibited the expression of myogenic miRNAs and suppressed the differentiation of C2C12 myoblasts to myocytes/myotubes in an NF-κB-dependent manner. This block in differentiation by TNFα was relieved by overexpression of miR-1, miR-206, or miR-133a/b. CONCLUSION: Taken together, these results provide a new mechanistic link between the action of proinflammatory cytokines and the degenerative pathology of inflammatory myopathies, and suggest therapeutic approaches for these diseases.

The plasma cell signature in autoimmune disease.

OBJECTIVE: Production of pathogenic autoantibodies by self-reactive plasma cells (PCs) is a hallmark of autoimmune diseases. We undertook this study to investigate the prevalence of PCs and their relationship to known pathogenic pathways to increase our understanding of the role of PCs in disease progression and treatment response. METHODS: We developed a sensitive gene expression-based method to overcome the challenges of measuring PCs using flow cytometry. Whole-genome microarray analysis of sorted cellular fractions identified a panel of genes, IGHA1, IGJ, IGKC, IGKV4-1, and TNFRSF17, expressed predominantly in PCs. The sensitivity of the PC signature score created from the combined expression levels of these genes was assessed through ex vivo experiments with sorted cells. This PC gene expression signature was used for monitoring changes in PC levels following anti-CD19 therapy, for evaluating the relationship between PCs and other autoimmune disease-related genes, and for estimating PC levels in affected blood and tissue from patients with multiple autoimmune diseases. RESULTS: The PC signature was highly sensitive and capable of detecting a change in as few as 360 PCs. The PC signature was reduced more than 90% in scleroderma patients following anti-CD19 treatment, and this reduction was highly correlated (r = 0.80) with inhibition of collagen gene expression. Evaluation of multiple autoimmune diseases revealed that 30-35% of lupus and rheumatoid arthritis patients had increased levels of PCs. CONCLUSION: This newly developed PC signature provides a robust and accurate method of measuring PC levels in the clinic. Our results highlight subsets of patients across multiple autoimmune diseases who may benefit from PC-depleting therapy.

MicroRNA-206 induces G1 arrest in melanoma by inhibition of CDK4 and Cyclin D.

Expression profiling of microRNAs in melanoma lesional skin biopsies compared with normal donor skin biopsies, as well as melanoma cell lines compared with normal melanocytes, revealed that hsa-miR-206 was down-regulated in melanoma (-75.4-fold, P = 1.7 × 10(-4)). MiR-206 has been implicated in a large number of cancers, including breast, lung, colorectal, ovarian, and prostate cancers; however, its role in tumor development remains largely unknown, its biologic function is poorly characterized, and its targets affecting cancer cells are largely unknown. MiR-206 reduced growth and migration/invasion of multiple melanoma cell lines. Bioinformatics identified cell cycle genes CDK2, CDK4, Cyclin C, and Cyclin D1 as strong candidate targets. Western blots and 3'UTR reporter gene assays revealed that miR-206 inhibited translation of CDK4, Cyclin D1, and Cyclin C. Additionally, hsa-miR-206 transfection induced G1 arrest in multiple melanoma cell lines. These observations support hsa-miR-206 as a tumor suppressor in melanoma and identify Cyclin C, Cyclin D1, and CDK4 as miR-206 targets.

A phase 1b clinical trial evaluating sifalimumab, an anti-IFN-α monoclonal antibody, shows target neutralisation of a type I IFN signature in blood of dermatomyositis and polymyositis patients.

OBJECTIVE: To assess the pharmacodynamic effects of sifalimumab, an investigational anti-IFN-α monoclonal antibody, in the blood and muscle of adult dermatomyositis and polymyositis patients by measuring neutralisation of a type I IFN gene signature (IFNGS) following drug exposure. METHODS: A phase 1b randomised, double-blinded, placebo controlled, dose-escalation, multicentre clinical trial was conducted to evaluate sifalimumab in dermatomyositis or polymyositis patients. Blood and muscle biopsies were procured before and after sifalimumab administration. Selected proteins were measured in patient serum with a multiplex assay, in the muscle using immunohistochemistry, and transcripts were profiled with microarray and quantitative reverse transcriptase PCR assays. A 13-gene IFNGS was used to measure the pharmacological effect of sifalimumab. RESULTS: The IFNGS was suppressed by a median of 53-66% across three time points (days 28, 56 and 98) in blood (p=0.019) and 47% at day 98 in muscle specimens post-sifalimumab administration. Both IFN-inducible transcripts and proteins were prevalently suppressed following sifalimumab administration. Patients with 15% or greater improvement from baseline manual muscle testing scores showed greater neutralisation of the IFNGS than patients with less than 15% improvement in both blood and muscle. Pathway/functional analysis of transcripts suppressed by sifalimumab showed that leucocyte infiltration, antigen presentation and immunoglobulin categories were most suppressed by sifalimumab and highly correlated with IFNGS neutralisation in muscle. CONCLUSIONS: Sifalimumab suppressed the IFNGS in blood and muscle tissue in myositis patients, consistent with this molecule's mechanism of action with a positive correlative trend between target neutralisation and clinical improvement. These observations will require confirmation in a larger trial powered to evaluate efficacy.

microRNA-mediated regulation of innate immune response in rheumatic diseases.

miRNAs have been shown to play essential regulatory roles in the innate immune system. They function at multiple levels to shape the innate immune response and maintain homeostasis by direct suppression of the expression of their target proteins, preferentially crucial signaling components and transcription factors. Studies in humans and in disease models have revealed that dysregulation of several miRNAs such as miR-146a and miR-155 in rheumatic diseases leads to aberrant production of and/or signaling by inflammatory cytokines and, thus, critically contributes to disease pathogenesis. In addition, the recent description of the role of certain extracellular miRNAs as innate immune agonist to induce inflammatory response would have direct relevance to rheumatic diseases.

Type I interferons in Sjögren's syndrome.

Sjögren's syndrome is a chronic autoimmune disease characterized by lymphocytic infiltration of the salivary and lachrymal glands resulting in dry eyes and mouth. Genetic predisposition, pathogenic infections and hormones have been implicated in the pathogenesis of the disease. Studies in the last several years have revealed marked over-expression of the type I interferon (IFN)-inducible genes in the peripheral blood and salivary glands of patients with Sjögren's syndrome. The expression of the type I IFN-inducible genes in Sjögren's syndrome also positively correlates to titers of anti-Ro and anti-La autoantibodies, which are typical for this disease. Plasmacytoid dendritic cells (pDC) are the major source of type I IFN production and activated pDC are detected in minor salivary gland biopsies from patients with primary Sjögren's syndrome. In addition, polymorphisms in genes important both for the production and response to type I IFN are associated to increased risk for Sjögren's syndrome. Because type I IFN bears a variety of biological functions, such as defense against viral infections and activation of the immune system, these results suggest that the type I IFN system has an important role in the pathogenesis of Sjögren's syndrome. A variety of mechanisms causing an activation of the type I IFN system are discussed in this review. Given the pivotal role of type I IFN in the disease process, therapeutic interventions targeting the type I IFN signaling pathway have the potential to benefit the patients with elevated type I IFN status and such hypothesis needs to be carefully evaluated in clinical development.

Genomic signatures characterize leukocyte infiltration in myositis muscles.

BACKGROUND: Leukocyte infiltration plays an important role in the pathogenesis and progression of myositis, and is highly associated with disease severity. Currently, there is a lack of: efficacious therapies for myositis; understanding of the molecular features important for disease pathogenesis; and potential molecular biomarkers for characterizing inflammatory myopathies to aid in clinical development. METHODS: In this study, we developed a simple model and predicted that 1) leukocyte-specific transcripts (including both protein-coding transcripts and microRNAs) should be coherently overexpressed in myositis muscle and 2) the level of over-expression of these transcripts should be correlated with leukocyte infiltration. We applied this model to assess immune cell infiltration in myositis by examining mRNA and microRNA (miRNA) expression profiles in muscle biopsies from 31 myositis patients and 5 normal controls. RESULTS: Several gene signatures, including a leukocyte index, type 1 interferon (IFN), MHC class I, and immunoglobulin signature, were developed to characterize myositis patients at the molecular level. The leukocyte index, consisting of genes predominantly associated with immune function, displayed strong concordance with pathological assessment of immune cell infiltration. This leukocyte index was subsequently utilized to differentiate transcriptional changes due to leukocyte infiltration from other alterations in myositis muscle. Results from this differentiation revealed biologically relevant differences in the relationship between the type 1 IFN pathway, miR-146a, and leukocyte infiltration within various myositis subtypes. CONCLUSIONS: Results indicate that a likely interaction between miR-146a expression and the type 1 IFN pathway is confounded by the level of leukocyte infiltration into muscle tissue. Although the role of miR-146a in myositis remains uncertain, our results highlight the potential benefit of deconvoluting the source of transcriptional changes in myositis muscle or other heterogeneous tissue samples. Taken together, the leukocyte index and other gene signatures developed in this study may be potential molecular biomarkers to help to further characterize inflammatory myopathies and aid in clinical development. These hypotheses need to be confirmed in separate and sufficiently powered clinical trials.

Biomarkers for systemic lupus erythematosus.

In recent years, biomarkers have shown significant promise in helping decision-making in drug development. Systemic lupus erythematosus (SLE) is a complicated and highly heterogeneous disease that involves all organs. Only one drug, belimumab, has been approved by the US Food and Drug Administration to treat SLE during the last 50 years and there remains a high unmet medical need to develop new and effective therapies to benefit different patient populations in SLE. Due to the extreme heterogeneity of the disease and the complex and rigorous process to validate individual biomarkers, there is currently a very limited number of consensus biomarkers to aid the treatment decision-making in SLE. This review provides a snapshot of some biomarkers in the field that have the potential to make a big impact on drug development and/or treatment decisions by physicians. These include: type I interferon (IFN) gene signature as a pharmacodynamic marker and potential predictive marker for anti-type I IFN therapy; anti-double stranded DNA as a disease marker and potential predictive marker for flares; the complements and neutrophil signatures as disease marker of SLE; and TWEAK (a tumor necrosis factor family member produced by macrophages) and MCP-1 as potential markers to predict renal flares. Most of these markers need carefully planned and prospective studies with high statistical power to confirm their respective utilities. With the development and application of powerful new technologies, more successful biomarkers will emerge in SLE. This could improve the management of patients in the clinic and facilitate the development of novel and more effective therapeutics for this difficult-to-treat disease.

TRAF6-dependent Act1 phosphorylation by the IκB kinase-related kinases suppresses interleukin-17-induced NF-κB activation.

Interleukin-17 (IL-17) is critically involved in the pathogenesis of various inflammatory disorders. IL-17 receptor (IL-17R)-proximal signaling complex (IL-17R-Act1-TRAF6) is essential for IL-17-mediated NF-κB activation, while IL-17-mediated mRNA stability is TRAF6 independent. Recently, inducible IκB kinase (IKKi) has been shown to phosphorylate Act1 on Ser 311 to mediate IL-17-induced mRNA stability. Here we show that TANK binding kinase 1 (TBK1), the other IKK-related kinase, directly phosphorylated Act1 on three other Ser sites to suppress IL-17R-mediated NF-κB activation. IL-17 stimulation activated TBK1 and induced its association with Act1. IKKi also phosphorylated Act1 on the three serine sites and played a redundant role with TBK1 in suppressing IL-17-induced NF-κB activation. Act1 phosphorylation on the three sites inhibited its association with TRAF6 and consequently NF-κB activation in IL-17R signaling. Interestingly, TRAF6, but not TRAF3, which is the upstream adaptor of the IKK-related kinases in antiviral signaling, was critical for IL-17-induced Act1 phosphorylation. TRAF6 was essential for IL-17-induced TBK1 activation, its association with Act1, and consequent Act1 phosphorylation. Our findings define a new role for the IKK-related kinases in suppressing IL-17-mediated NF-κB activation through TRAF6-dependent Act1 phosphorylation.

Identification of microRNA-31 as a novel regulator contributing to impaired interleukin-2 production in T cells from patients with systemic lupus erythematosus.

OBJECTIVE: MicroRNAs (miRNAs) function to fine-tune the control of immune cell signaling. It is well established that there are abnormalities in the interleukin-2 (IL-2)-related signaling pathways in systemic lupus erythematosus (SLE). The miR-31 microRNA has been found to be markedly underexpressed in patients with SLE, and thus the present study was undertaken to investigate the role of miR-31 in IL-2 defects in lupus T cells. METHODS: Expression levels of miR-31 were quantitated using TaqMan miRNA assays. Transfection and stimulation of cultured cells followed by TaqMan quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and reporter gene assays were conducted to determine the biologic function of miR-31. NF-AT nuclear translocation and expression were quantitatively measured using an ImageStream cytometer. Bioinformatics analysis, small interfering RNA (siRNA) knockdown, and Western blotting were performed to validate miR-31 targets and effects. RESULTS: The expression of miR-31 was significantly decreased in lupus T cells, and this was positively correlated with the expression of IL-2. Overexpression of miR-31 in T cells increased the production of IL-2 by altering NF-AT nuclear expression and IL2 promoter activity, while knockdown of endogenous miR-31 reduced IL-2 production. RhoA expression was directly repressed by miR-31 in T cells. Of note, siRNA-mediated knockdown of RhoA enhanced IL2 promoter activity and, consequently, up-regulated IL-2 production. RhoA expression was consistently up-regulated and negatively correlated with the levels of miR-31 in lupus T cells. Manipulation of miR-31 expression in lupus T cells restored the expression of IL-2 at both the messenger RNA and protein levels. CONCLUSION: MicroRNA-31 is a novel enhancer of IL-2 production during T cell activation. Dysregulation of miR-31 and its target, RhoA, could be a novel molecular mechanism underlying the IL-2 deficiency in patients with SLE.

EphB4 promotes or suppresses Ras/MEK/ERK pathway in a context-dependent manner: Implications for EphB4 as a cancer target.

EphB4 is a member of the Eph receptor tyrosine kinase family shown to act in neuronal guidance and mediate venal/arterial separation. In contrast to these more established roles, EphB4's function in cancer is much less clear. Here we illustrate both tumor promoting as well as suppressing roles of EphB4, by showing that its activation resulted in inhibition of the Ras/ERK pathway in endothelial cells but activation of the same pathway in MCF-7 breast cancer cells. This was true if EphB4 was stimulated with EphrinB2, its natural ligand, or an agonistic monoclonal antibody for EphB4. Correspondingly, EphB4 activation stimulated MCF7 growth while inhibiting HUVEC cell proliferation. The reason for these dramatic differences is due to functional coupling of EphB4 to different downstream effectors. Reduction of p120 RasGAP in HUVEC cells attenuated the inhibitory effect of EphB4 activation on the ERK pathway, whereas knockdown of PP2A in MCF7 cells attenuated EphB4 activation of the ERK pathway. This represents the first time a functional coupling between Eph receptor and PP2A has been demonstrated leading to activation of an oncogenic pathway. Our study illustrates the caveats and potential challenges of targeting EphB4 for cancer therapy due to the conflicting effects on cancer cell and endothelial cell compartments.

MEDI3617, a human anti-angiopoietin 2 monoclonal antibody, inhibits angiogenesis and tumor growth in human tumor xenograft models.

Angiopoietin 2 (Ang2) is an important regulator of angiogenesis, blood vessel maturation and integrity of the vascular endothelium. The correlation between the dynamic expression of Ang2 in tumors with regions of high angiogenic activity and a poor prognosis in many tumor types makes Ang2 an ideal drug target. We have generated MEDI3617, a human anti-Ang2 monoclonal antibody that neutralizes Ang2 by preventing its binding to the Tie2 receptor in vitro, and inhibits angiogenesis and tumor growth in vivo. Treatment of mice with MEDI3617 resulted in inhibition of angiogenesis in several mouse models including: FGF2-induced angiogenesis in a basement extract plug model, tumor and retinal angiogenesis. In xenograft tumor models, treatment with MEDI3617 resulted in a reduction in tumor angiogenesis and an increase in tumor hypoxia. The administration of MEDI3617 as a single agent to mice bearing human tumor xenografts resulted in tumor growth inhibition against a broad spectrum of tumor types. Combining MEDI3617 with chemotherapy or bevacizumab resulted in a delay in tumor growth and no body weight loss was observed in the combination groups. These results, combined with pharmacodynamic studies, demonstrate that treatment of tumor-bearing mice with MEDI3617 significantly inhibited tumor growth as a single agent by blocking tumor angiogenesis. Together, these data show that MEDI3617 is a robust antiangiogenic agent and support the clinical evaluation and biomarker development of MEDI3617 in cancer patients.

Identification of activated cytokine pathways in the blood of systemic lupus erythematosus, myositis, rheumatoid arthritis, and scleroderma patients.

AIM: To develop genomic signatures of seven cytokines involved in the pathogenesis of rheumatic diseases such as systemic lupus erythematosus (SLE), dermatomyositis (DM), polymyositis (PM), rheumatoid arthritis (RA), or systemic scleroderma (SSc) that could potentially help identify patients likely to respond to therapies that target these individual cytokines. METHODS: Over-expressed transcripts in the whole blood (WB) were identified from 262 SLE, 44 DM, 33 PM, 38 SSc and 89 RA subjects and compared to 24 healthy subjects using Affymetrix arrays. Cytokine-inducible gene signatures such as type I interferon (IFN), tumor necrosis factor alpha (TNF-α), interleukin (IL)-1ß, IL-10, IL-13, IL-17, and granulocyte-macrophage colony-stimulating factor (GM-CSF) were assessed in the WB of these subjects to identify subpopulations showing activation of specific cytokine pathways. RESULTS: Significant activation of the type I IFN pathway in a population of five diseases studied was universally observed. The TNF-α and IL-1ß pathways were activated in subgroups of PM and RA subjects, respectively, with another subgroup of RA subjects showing activation of the IL-13 pathway. The GM-CSF pathway was activated in a subgroup of SSc subjects and the IL-17 pathway was activated in subgroups of all diseases except SLE. CONCLUSIONS: A novel gene expression measurement of activated cytokines in five different rheumatic diseases is presented. Characterizing the cytokine pathways most activated in specific patient subpopulations has the potential to help target the appropriate patient populations for corresponding anti-cytokine therapies.

Targeting the insulin-like growth factor axis for the development of novel therapeutics in oncology.

Insulin-like growth factors (IGF) are polypeptide hormones with potent anabolic and mitogenic effects that regulate cell growth and differentiation. Dysregulation of the IGF axis has been well documented in the development and progression of multiple types of cancer. As a result, compounds targeting the IGF axis have become an area of intense preclinical and clinical research for cancer therapeutics. The IGF axis is intimately involved with the insulin-signaling pathway because of their close homologies. This homology may explain hurdles encountered in the clinical development of IGF-targeted therapies, such as less-than-expected antitumor efficacy that may arise from compensatory increases in the activity of insulin receptor isoform A (IR-A), in response to IGF-I receptor (IGF-IR) inhibition and perturbations in glucose homeostasis, arising from the inhibition of insulin receptor isoform B (IR-B) activity. In this brief review, we compare differentiating factors that characterize the 3 major classes of IGF-targeting compounds: therapeutic antibodies that target IGF-IR, small molecule tyrosine kinase inhibitors that inhibit kinase activities of IGF-IR and IR, and antibodies that target IGF ligands.