Vascular Endothelial Growth Factor Ligand Research Articles

Interactions between NRP1 and VEGFR2 molecules in the plasma membrane

Here we use a quantitative FRET approach, specifically developed to probe membrane protein interactions, to study the homo-association of neuropilin 1 (NRP1) in the plasma membrane, as well as its hetero-interactions with vascular endothelial growth factor receptor 2 (VEGFR2). Experiments are performed both in the absence and presence of the soluble ligand vascular endothelial growth factor A (VEGFA), which binds to both VEGFR2 and NRP1. We demonstrate the presence of homo-interactions between NRP1 molecules, as well as hetero-interactions between NRP1 and VEGFR2 molecules, in the plasma membrane. Our results underscore the complex nature of the interactions between self-associating receptors, co-receptors, and their ligands in the plasma membrane. They also highlight the need for new methodologies that capture this complexity, and the need for precise physiological measurements of local receptor surface densities in the membrane of cells. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.

A predictive value of von Willebrand factor for early response to Bevacizumab therapy in recurrent glioma.

Bevacizumab (BV), a neutralizing monoclonal antibody against the vascular endothelial growth factor ligand, is recognized as a potent anti-angiogenic agent with antitumor activity. The aim of this single-center, retrospective, longitudinal study was to investigate the possible predictive value of baseline demographic, clinical and laboratory parameters for early 3-month response to BV therapy in patients with recurrent glioma. Forty-nine patients with recurrent glioma received BV at 10mg/kg intravenously every 3weeks alone or in association with chemotherapy were included in this study. Blood samples were collected from all patients before the first (baseline), the second and the third administration of BV. After 3months of BV therapy, patients with partial response were defined as responders whereas patients with stable or progressive disease were defined as non-responders. The median overall follow-up was 8months (range 1-73), the median overall survival (OS) was 8months (95% CI 6-10) and the median progression free survival (PFS) was 4months (95% CI 3-5). Thirty-five % of patients were responders and showed significantly lower von Willebrand factor (VWF) levels than non-responders at all sample times (p < .02 for all). Also, on multivariate analysis the baseline VWF value was the only predictor for an early response to BV therapy. Furthermore, D-dimer and prothrombin fragment 1+2 were predictive factors for OS while Karnofsky performance status resulted predictive for PFS. VWF antigen value is a possible predictive biomarker for an early 3-month response to BV therapy in recurrent glioma.

Immunoglobulin Fc-Fused Peptide without C-Terminal Arg or Lys Residue Augments Neuropilin-1-Dependent Tumor Vascular Permeability.

Neuropilin-1 (NRP1), which functions as a coreceptor for vascular endothelial growth factor (VEGF) and is implicated in vascular permeability and tumorigenesis, has been targeted by peptides that specifically bind to the VEGF-binding region on NRP1. Like natural VEGF ligands, all known peptides with NRP1-binding activity bind only through a carboxy (C)-terminal R/K-x-x-R/K sequence motif (x stands for any amino acids); this strict requirement is called the C-end rule (CendR). Here, we report immunoglobulin Fc-fused NRP1-specific peptides deviating from CendR. We screened a yeast surface-displayed Fc-fused non-CendR peptide library against NRP1 and isolated Fc-V12, wherein V12 peptide comprising 12 amino acids has a PPRV sequence at its C-terminal end. Although Fc-V12 lacked the CendR motif, it showed selective binding to the VEGF-binding region of NRP1 and triggered cellular internalization of NRP1, which resulted in enhanced extravasation into tumor tissues and tumor tissue penetration of the Fc-fused peptide along with the coinjected chemical drug in tumor-bearing mice. Through a saturation mutagenesis study, we identified that the Val residue at the C-terminus of Fc-V12 is crucial for NRP1 binding. We further improved NRP1 affinity of Fc-V12 (KD = ∼761 nM) through directed evolution of the upstream sequence of PPRV to obtain Fc-V12-33 (KD = ∼17.4 nM), which exhibited enhanced NRP1-mediated vascular permeability as compared with Fc-V12. Our results provide functional Fc-fused non-CendR peptides, which bind to the VEGF-binding region of NRP1 and enhance vascular permeability, expanding the sequence space of NRP1-targeting peptides.

Targeting VEGF receptors with non-neutralizing cyclopeptides for imaging applications.

Pharmacological strategies aimed at preventing cancer growth are in most cases paralleled by diagnostic investigations for monitoring and prognosticating therapeutic efficacy. A relevant approach in cancer is the suppression of pathological angiogenesis, which is principally driven by vascular endothelial growth factor (VEGF) or closely related factors and by activation of specific receptors, prevailingly VEGFR1 and VEGFR2, set on the surface of endothelial cells. Monitoring the presence of these receptors in vivo is henceforth a way to predict therapy outcome. We have designed small peptides able to bind and possibly antagonize VEGF ligands by targeting VEGF receptors. Peptide systems have been designed to be small, cyclic and to host triplets of residues known to be essential for VEGF receptors recognition and we named them 'mini-factors'. They have been structurally characterized by CD, NMR and molecular dynamics (MD) simulations. Mini-factors do bind with different specificity and affinity VEGF receptors but none blocks receptor activity. Following derivatization with suitable tracers they have been employed as molecular probes for sensing receptors on cell surface without affecting their activity as is usually observed with other binders having neutralizing activity.

Abstract 24035: Human iPSC-Derived Endothelial Cells Predict Predilection to Atherogenesis by Endothelial Proinflammatory Activation

Introduction: Coronary artery disease (CAD), the direct outcome of atherosclerosis, is the leading cause of death in the United States. Previous studies demonstrated that impaired function of aldehyde dehydrogenase 2 (ALDH2), a key enzyme for alcohol metabolism, is linked to increased susceptibility to CAD. A single-nucleotide polymorphism that generates E487K mutation (ALDH2*2) reduces enzymatic activity of ALDH2 to less than 40% of the wild type (WT) and is present in ~560 million people. However, it remains unclear how ALDH2 regulates atherosclerotic progression. Hypothesis: Recent studies suggest a critical role of ALDH2 in plaque development and endothelial activation. Therefore, we hypothesize that endothelial cells of ALDH2*2 carriers possess greater susceptibility to proinflammatory activation, whereby endothelial cells recruit immune cells, leading to increased risk of atherogenesis. Methods: To study the patient-specific effects of ALDH2*2 mutation on endothelial proinflammatory activation, we generated and characterized iPSC-derived endothelial cells (iPSC-ECs) from 5 WT subjects and 5 ALDH2*2 carriers. We exposed the iPSC-ECs to pro-inflammatory conditions and assessed the level of endothelial proinflammatory activation by gene expression analysis and monocyte adhesion assay. Results: Our preliminary data show ALDH2*2-iPSC-ECs exhibit impaired ALDH2 function resulting in metabolic dysregulation compared to WT. Presence of ALDH2*2 mutation resulted in enhanced inflammatory response in the iPSC-ECs when treated with proinflammatory cytokines such as TNFα and IL-1β, as evidenced by up-regulation of cell adhesion molecules and augmented adherence to monocytes. The ALDH2*2-iPSC-ECs also exhibited an increased basal expression of vascular endothelial growth factor receptor 1 (FLT1) gene, which was further augmented upon inflammatory stimulation. FLT1 is a receptor for vascular endothelial growth factor ligands, playing a critical role in endothelial homeostasis and biology. Conclusion: Taken together, we elucidate the effects of impaired ALDH2 function on increased susceptibility to atherogenesis by endothelial proinflammatory activation using patient-derived iPSC-ECs.

Bevacizumab for ramucirumab refractory malignant pleural effusion in non-small cell lung cancer: a case report and review of the literature

Malignant pleural effusion (MPE) is a major problem associated with advanced non-small cell lung cancer for which an optimum treatment strategy has yet to be determined. Notably, vascular endothelial growth factor (VEGF) signaling has been found to influence MPE, and bevacizumab, a VEGF ligand inhibitor, can effectively control MPE. Ramucirumab, a human monoclonal antibody specific for VEGF receptor-2, has recently been approved for advanced non-small cell lung cancer. However, it remains unclear which of these agents more effectively control MPE.We describe a case of a 68-year-old man with advanced non-small cell lung cancer in whom ramucirumab plus docetaxel-refractory MPE was responsive to bevacizumab plus docetaxel combination therapy. The patient’s MPE progressed after two cycles of ramucirumab plus docetaxel second-line chemotherapy. After switching to bevacizumab plus docetaxel, a computed tomography scan revealed a decreased MPE after two cycles of treatment.Bevacizumab may be more effective for treating MPE. However, further investigations are still warranted to determine the optimal VEGF-targeted agent for this condition.

Mathematical Modeling of Cellular Cross-Talk Between Endothelial and Tumor Cells Highlights Counterintuitive Effects of VEGF-Targeted Therapies.

Tumor growth and progression are critically dependent on the establishment of a vascular support system. This is often accomplished via the expression of pro-angiogenic growth factors, including members of the vascular endothelial growth factor (VEGF) family of ligands. VEGF ligands are overexpressed in a wide variety of solid tumors and therefore have inspired optimism that inhibition of the different axes of the VEGF pathway-alone or in combination-would represent powerful anti-angiogenic therapies for most cancer types. When considering treatments that target VEGF and its receptors, it is difficult to tease out the differential anti-angiogenic and anti-tumor effects of all combinations experimentally because tumor cells and vascular endothelial cells are engaged in a dynamic cross-talk that impacts key aspects of tumorigenesis, independent of angiogenesis. Here we develop a mathematical model that connects intracellular signaling responsible for both endothelial and tumor cell proliferation and death to population-level cancer growth and angiogenesis. We use this model to investigate the effect of bidirectional communication between endothelial cells and tumor cells on treatments targeting VEGF and its receptors both in vitro and in vivo. Our results underscore the fact that in vitro therapeutic outcomes do not always translate to the in vivo situation. For example, our model predicts that certain therapeutic combinations result in antagonism in vivo that is not observed in vitro. Mathematical modeling in this direction can shed light on the mechanisms behind experimental observations that manipulating VEGF and its receptors is successful in some cases but disappointing in others.

Mesenchymal Stem Cell‐Derived Extracellular Vesicles Improve the Renal Microvasculature in Coexisting Metabolic Syndrome and Renovascular Disease in Swine

BackgroundSuperimposition of the metabolic syndrome (MetS) on renovascular disease (RVD) amplifies intrarenal microvascular loss. Extracellular vesicles (EVs) released from adipose tissue‐derived mesenchymal stem/stromal cells (MSCs) may mediate their paracrine effect, but their efficacy to protect the renal microcirculation in RVD complicated by MetS remains unclear. Using a novel swine model, we tested the hypothesis that EVs would attenuate microvascular loss in MetS+RVD.MethodsFour groups of pigs (n=7 each) were studied after 16 weeks of diet‐induced MetS and unilateral RVD (MetS+RVD), MetS+RVD treated 4 weeks earlier with a single intra‐renal delivery of pre‐labeled EVs harvested from autologous MSCs, and Lean and MetS Sham controls. Stenotic‐kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were measured in‐vivo (fast CT), whereas EV characteristics, renal microvascular architecture (micro‐CT), and injury pathways ex‐vivo.ResultsmRNA sequencing of EVs and their parent MSCs revealed that EVs were enriched with pro‐angiogenic genes, including vascular endothelial growth factor (VEGF)‐A, VEGF–C, and Von Willebrand Factor (vWF)‐A Domain Containing‐1 (VWA)‐1 (Figure A). In addition, protein expression of VEGF and vWF was higher in EVs compared to MSCs (Figure B). EVs were detected in the stenotic‐kidney ex‐vivo internalized by tubular and endothelial cells. EVs restored renal expression of the pro‐angiogenic factors VEGF, Notch‐1, and Notch ligand delta‐like‐4 (DLL4) and improved cortical microvascular density (Figure C–D). Tubulointerstitial fibrosis increased and RBF and GFR decreased in MetS+RVD vs. MetS, but were restored in MetS+RVD+EV (Figure E–F).ConclusionsIntra‐renal delivery of MSC‐derived EVs bearing pro‐angiogenic properties in swine MetS+RVD restored stenotic‐kidney microcirculation, and in turn its hemodynamics and function. Our study suggests a novel therapeutic potential for MSC‐derived EVs in restoring renal function in chronic experimental MetS+RVD.Support or Funding InformationThis study was partly supported by NIH grant numbers DK73608, DK104273, HL123160, and DK102325, DK106427, the Mayo Clinic Center for Regenerative Medicine, and the Mayo Clinic Mary Kathryn and Michael B. Panitch Career Development Award.

Expression of Semaphorins, Neuropilins, VEGF, and Tenascins in Rat and Human Primary Sensory Neurons after a Dorsal Root Injury

Dorsal root injury is a situation not expected to be followed by a strong regenerative growth, or growth of the injured axon into the central nervous system of the spinal cord, if the central axon of the dorsal root is injured but of strong regeneration if subjected to injury to the peripherally projecting axons. The clinical consequence of axonal injury is loss of sensation and may also lead to neuropathic pain. In this study, we have used in situ hybridization to examine the distribution of mRNAs for the neural guidance molecules semaphorin 3A (SEMA3A), semaphorin 3F (SEMA3F), and semaphorin 4F (SEMA4F), their receptors neuropilin 1 (NP1) and neuropilin 2 (NP2) but also for the neuropilin ligand vascular endothelial growth factor (VEGF) and Tenascin J1, an extracellular matrix molecule involved in axonal guidance, in rat dorsal root ganglia (DRG) after a unilateral dorsal rhizotomy (DRT) or sciatic nerve transcetion (SNT). The studied survival times were 1–365 days. The different forms of mRNAs were unevenly distributed between the different size classes of sensory nerve cells. The results show that mRNA for SEMA3A was diminished after trauma to the sensory nerve roots in rats. The SEMA3A receptor NP1, and SEMA3F receptor NP2, was significantly upregulated in the DRG neurons after DRT and SNT. SEMA4F was upregulated after a SNT. The expression of mRNA for VEGF in DRG neurons after DRT showed a significant upregulation that was high even a year after the injuries. These data suggest a role for the semaphorins, neuropilins, VEGF, and J1 in the reactions after dorsal root lesions.

Engineered ligand-based VEGFR antagonists with increased receptor binding affinity more effectively inhibit angiogenesis.

Pathologic angiogenesis is mediated by the coordinated action of the vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor 2 (VEGFR2) signaling axis, along with crosstalk contributed by other receptors, notably αvβ3 integrin. We build on earlier work demonstrating that point mutations can be introduced into the homodimeric VEGF ligand to convert it into an antagonist through disruption of binding to one copy of VEGFR2. This inhibitor has limited potency, however, due to loss of avidity effects from bivalent VEGFR2 binding. Here, we used yeast surface display to engineer a variant with VEGFR2 binding affinity approximately 40‐fold higher than the parental antagonist, and 14‐fold higher than the natural bivalent VEGF ligand. Increased VEGFR2 binding affinity correlated with the ability to more effectively inhibit VEGF‐mediated signaling, both in vitro and in vivo, as measured using VEGFR2 phosphorylation and Matrigel implantation assays. High affinity mutations found in this variant were then incorporated into a dual‐specific antagonist that we previously designed to simultaneously bind to and inhibit VEGFR2 and αvβ3 integrin. The resulting dual‐specific protein bound to human and murine endothelial cells with relative affinities of 120 ± 10 pM and 360 ± 50 pM, respectively, which is at least 30‐fold tighter than wild‐type VEGF (3.8 ± 0.5 nM). Finally, we demonstrated that this engineered high‐affinity dual‐specific protein could inhibit angiogenesis in a murine corneal neovascularization model. Taken together, these data indicate that protein engineering strategies can be combined to generate unique antiangiogenic candidates for further clinical development.

Neuropilin-1 Is Expressed on Lymphoid Tissue Residing LTi-like Group 3 Innate Lymphoid Cells and Associated with Ectopic Lymphoid Aggregates

SummaryHere, we characterize a subset of ILC3s that express Neuropilin1 (NRP1) and are present in lymphoid tissues, but not in the peripheral blood or skin. NRP1+ group 3 innate lymphoid cells (ILC3s) display in vitro lymphoid tissue inducer (LTi) activity. In agreement with this, NRP1+ ILC3s are mainly located in proximity to high endothelial venules (HEVs) and express cell surface molecules involved in lymphocyte migration in secondary lymphoid tissues via HEVs. NRP1 was also expressed on mouse fetal LTi cells, indicating that NRP1 is a conserved marker for LTi cells. Human NRP1+ ILC3s are primed cells because they express CD45RO and produce higher amounts of cytokines than NRP1− cells, which express CD45RA. The NRP1 ligand vascular endothelial growth factor A (VEGF-A) served as a chemotactic factor for NRP1+ ILC3s. NRP1+ ILC3s are present in lung tissues from smokers and patients with chronic obstructive pulmonary disease, suggesting a role in angiogenesis and/or the initiation of ectopic pulmonary lymphoid aggregates.

The Role of the Antiangiogenetic Ramucirumab in the Treatment of Advanced Non Small Cell Lung Cancer.

Angiogenesis is one of the most important phenomena sustaining tumor development and metastatization, including for non small cell lung cancer (NSCLC). A dominant role in angiogenesis is played by the vascular endothelial growth factor (VEGF) and its signaling pathway. Ramucirumab, is a fully human immunoglobulin G1 monoclonal antibody that binds to the extracellular domain of the VEGF receptor-2 (VEGFR-2) with high specificity and affinity blocking the interaction of VEGFR-2 and VEGF ligands, thus inhibiting their signaling pathways and the consequential endothelial proliferation and migration. A recent phase III randomized trial named REVEL, demonstrated the efficacy of ramucirumab in combination with docetaxel as second line treatment of advanced NSCLC, leading to its FDA and EMA approval in this clinical setting. In the REVEL trial advanced NSCLC patients whose disease had progressed after first line platinum-based chemotherapy, were administered ramucirumab plus docetaxel or placebo plus docetaxel. More than 1,250 patients were treated and patients randomized to the treatment with ramucirumab plus docetaxel showed a significant longer median overall survival compared to those randomized to chemotherapy only. Ramucirumab is the first antiangiogenetic agent approved in the treatment both of squamous and non squamous NSCLC. In fact, it is not associated with increased risk of respiratory bleeding in the squamous histology, and also has demonstrated efficacy in both histology types. The role of ramucirumab, already cleared in the second-line treatment of advanced NSCLC, needs to be clarified further and is currently being explored also in the first-line treatment of advanced NSCLC.

Anti-angiogenic Therapy in Patients with Advanced Gastric and Gastroesophageal Junction Cancer: A Systematic Review.

Despite advancements in therapy for advanced gastric and gastroesophageal junction cancers, their prognosis remains dismal. Tumor angiogenesis plays a key role in cancer growth and metastasis, and recent studies indicate that pharmacologic blockade of angiogenesis is a promising approach to therapy. In this systematic review, we summarize current literature on the clinical benefit of anti-angiogenic agents in advanced gastric cancer. We conducted a systematic search of PubMed and conference proceedings including the American Society of Clinical Oncology, the European Society for Medical Oncology, and the European Cancer Congress. Included studies aimed to prospectively evaluate the efficacy and safety of anti-angiogenic agents in advanced gastric or gastroesophageal junction cancer. Each trial investigated at least one of the following endpoints: overall survival, progression-free survival/time to progression, and/or objective response rate. Our search yielded 139 publications. Forty-two met the predefined inclusion criteria. Included studies reported outcomes with apatinib, axitinib, bevacizumab, orantinib, pazopanib, ramucirumab, regorafenib, sorafenib, sunitinib, telatinib, and vandetanib. Second-line therapy with ramucirumab and third-line therapy with apatinib are the only anti-angiogenic agents so far shown to significantly improve survival of patients with advanced gastric cancer. Overall, agents that specifically target the vascular endothelial growth factor ligand or receptor have better safety profile compared to multi-target tyrosine kinase inhibitors.

Excess HB-EGF, which promotes VEGF signaling, leads to hydrocephalus.

Heparin binding epidermal growth factor-like growth factor (HB-EGF) is an angiogenic factor mediating radial migration of the developing forebrain, while vascular endothelial growth factor (VEGF) is known to influence rostral migratory stream in rodents. Cell migratory defects have been identified in animal models of hydrocephalus; however, the relationship between HB-EGF and hydrocephalus is unclear. We show that mice overexpressing human HB-EGF with β-galactosidase reporter exhibit an elevated VEGF, localization of β-galactosidase outside the subventricular zone (SVZ), subarachnoid hemorrhage, and ventriculomegaly. In Wistar polycystic kidney rats with hydrocephalus, alteration of migratory trajectory is detected. Furthermore, VEGF infusions into the rats result in ventriculomegaly with an increase of SVZ neuroblast in rostral migratory stream, whereas VEGF ligand inhibition prevents it. Our results support the idea that excess HB-EGF leads to a significant elevation of VEGF and ventricular dilatation. These data suggest a potential pathophysiological mechanism that elevated HB-EGF can elicit VEGF induction and hydrocephalus.

Prospective Preliminary In Vitro Investigation of a Magnetic Iron Oxide Nanoparticle Conjugated with Ligand CD80 and VEGF Antibody As a Targeted Drug Delivery System for the Induction of Cell Death in Rodent Osteosarcoma Cells.

Target drug deliveries using nanotechnology are a novel consideration in the treatment of cancer. We present herein an in vitro mouse model for the preliminary investigation of the efficacy of an iron oxide nanoparticle complex conjugated to vascular endothelial growth factor (VEGF) antibody and ligand cluster of differentiation 80 (CD80) for the purpose of eventual translational applications in the treatment of human osteosarcoma (OSA). The 35 nm diameter iron oxide magnetic nanoparticles are functionalized with an n-hydroxysuccinimide biocompatible coating and are conjugated on the surface to proteins VEGF antibody and ligand CD80. Combined, these proteins have the ability to target OSA cells and induce apoptosis. The proposed system was tested on a cancerous rodent osteoblast cell line (ATCCTMNPO CRL-2836) at four different concentrations (0.1, 1.0, 10.0, and 100.0 μg/mL) of ligand CD80 alone, VEGF antibody alone, and a combination thereof (CD80+VEGF). Systems were implemented every 24 h over different sequential treatment timelines: 24, 48, and 72 h, to find the optimal protein concentration required for a reduction in cell proliferation. Results demonstrated that a combination of ligand CD80 and VEGF antibody was consistently most effective at reducing aberrant osteoblastic proliferation for both the 24- and 72-h timelines. At 48 h, however, an increase in cell proliferation was documented for the 0.1 and 1 μg/mL groups. For the 24- and 72-h tests, concentrations of 1.0 μg/mL of CD80+VEGF and 0.1 μg/mL of VEGF antibody were most effective. Concentrations of 10.0 and 100.0 μg/mL of CD80+VEGF reduced cell proliferation, but not as remarkably as the 1.0 μg/mL concentration. In addition, cell proliferation data showed that multiple treatments (72-h test) induced cell death in the osteoblasts better than a single treatment. Future targeted drug delivery system research includes trials in OSA cell lines from greater phylum species having spontaneous OSA, such as the dog, and on a human OSA cell line model.

Risk of adverse events with bevacizumab addition to therapy in advanced non-small-cell lung cancer: a meta-analysis of randomized controlled trials

BackgroundBevacizumab, a monoclonal antibody against vascular endothelial growth factor ligand, has shown survival benefits in the treatment of many types of malignant tumors, including non-small-cell lung cancer (NSCLC). We conducted this systematic review and meta-analysis to investigate the risk of the most clinically relevant adverse events related to bevacizumab in advanced NSCLC.MethodsDatabases from PubMed, Web of Science, and Cochrane Library up to August 2015, were searched to identify relevant studies. We included prospective randomized controlled Phase II/III clinical trials that compared therapy with or without bevacizumab for advanced NSCLC. Summary relative risk (RR) and 95% confidence intervals were calculated using random effects or fixed effects according to the heterogeneity among included trials.ResultsA total of 3,745 patients from nine clinical trials were included in the meta-analysis. Summary RRs showed a statistically significant bevacizumab-associated increased risk in three of the adverse outcomes studied: proteinuria (RR =7.55), hypertension (RR =5.34), and hemorrhagic events (RR =2.61). No statistically significant differences were found for gastrointestinal perforation (P=0.60), arterial and venous thromboembolic events (P=0.35 and P=0.92, respectively), or fatal events (P=0.29).ConclusionThe addition of bevacizumab to therapy in advanced NSCLC did significantly increase the risk of proteinuria, hypertension, and hemorrhagic events but not arterial/venous thromboembolic events, gastrointestinal perforation, or fatal adverse events.

Aminoacyl-Transfer RNA Synthetase Deficiency Promotes Angiogenesis via the Unfolded Protein Response Pathway.

Understanding the mechanisms regulating normal and pathological angiogenesis is of great scientific and clinical interest. In this report, we show that mutations in 2 different aminoacyl-transfer RNA synthetases, threonyl tRNA synthetase (tars(y58)) or isoleucyl tRNA synthetase (iars(y68)), lead to similar increased branching angiogenesis in developing zebrafish. The unfolded protein response pathway is activated by aminoacyl-transfer RNA synthetase deficiencies, and we show that unfolded protein response genes atf4, atf6, and xbp1, as well as the key proangiogenic ligand vascular endothelial growth factor (vegfaa), are all upregulated in tars(y58) and iars(y68) mutants. Finally, we show that the protein kinase RNA-like endoplasmic reticulum kinase-activating transcription factor 4 arm of the unfolded protein response pathway is necessary for both the elevated vegfaa levels and increased angiogenesis observed in tars(y58) mutants. Our results suggest that endoplasmic reticulum stress acts as a proangiogenic signal via unfolded protein response pathway-dependent upregulation of vegfaa.

A novel association of neuropilin-1 and MUC1 in pancreatic ductal adenocarcinoma: role in induction of VEGF signaling and angiogenesis.

We report that MUC1, a transmembrane glycoprotein that is overexpressed in >80% of pancreatic ductal adenocarcinoma (PDA) induced a pro-angiogenic tumor microenvironment by increasing the levels of neuropilin-1 (NRP1, a co-receptor of VEGF) and its ligand, VEGF. Expression of tumor-associated MUC1 (tMUC1) positively correlated with NRP1 levels in human and mouse PDA. Further, tMUC1hi PDA cells secreted high levels of VEGF and expressed high levels of VEGF receptor 2 and its phosphorylated forms as compared to tMUC1low/null PDA. This enabled the tMUC1hi/NRP1hi PDA cells to a) induce endothelial cell tube formation, b) generate long ectopic blood vessels and c) enhance distant metastasis in a zebrafish xenograft model. Concurrently, the proteins associated with epithelial to mesenchymal transition, N-cadherin and Vimentin, were highly induced in these tMUC1/NRP1hi PDA cells. Hence, blocking signaling via the NRP1-VEGF axis significantly reduced tube formation, new vessel generation, and metastasis induced by tMUC1hi PDA cells. Finally, we show that blocking the interaction between VEGF165 and NRP1 with a NRP1 antagonist significantly reduced VEGFR signaling and PDA tumor growth in vivo. Taken together, our data suggests a novel molecular mechanism by which tMUC1 may modulate NRP1-dependent VEGFR signaling in PDA cells.

Spotlight on bevacizumab in metastatic colorectal cancer: patient selection and perspectives.

Metastatic colorectal cancer (mCRC) is a prevalent disease for which combination cytotoxic chemotherapy is the mainstay of treatment. With the use of targeted therapy, including anti-angiogenic agents, there have been significant improvements in overall outcome of patients with mCRC. Bevacizumab, a monoclonal antibody targeting the vascular endothelial growth factor ligand A, is approved for use in mCRC patients in both the first and second lines of therapy. With a better understanding of the disease through molecular profiling, identification of prognostic biomarkers may lead to better patient selection with improved outcomes for those affected by this disease.

ATNT-09BEVACIZUMAB FOR METASTATIC DURAL AND ORBITAL ESTHESIONEUROBLASTOMA

Esthesioneuroblastoma is a malignant neuroectodermal tumor originating from the olfactory neuroepithelium. Bevacizumab is a specific inhibitor of the vascular endothelial growth factor ligand, preventing its interaction with receptors on endothelial cells. We report two cases of metastatic dural esthesioneuroblastoma that responded to bevacizumab. Patient 1, a 45 year-old man, had been treated initially for local disease with resection and radiation therapy (RT); for submandibular recurrence with radical neck dissection, RT, and cis-platinum plus etoposide; and subsequently for leptomeningeal disease with temozolomide plus sunitinib. He had an enlarging right orbital mass with progressive dural and leptomeningeal involvement. Patient 2, a 66 year-old woman, had been treated initially for local disease with craniotomy, RT, and cis-platinum; then for local recurrence with both regional and stereotactic RT. She developed enlarging orbital, dural and scalp masses. Both patients were treated with bevacizumab, 5 mg/kg every 2 weeks. Patient 1 achieved a partial response, with reduction in dural contrast enhancement, tumor cyst volumes, and perilesional edema, along with improvement in left leg weakness and right ptosis. His tumors progressed on imaging after 260 days of therapy. He died after 602 days of bevacizumab despite the addition of lomustine. Patient 2 achieved stable disease for 457 days but died of respiratory complications after developing a cerebrospinal fluid leak, without tumor progression. These patients with metastatic orbital and dural esthesioneuroblastoma achieved durable responses with bevacizumab therapy. Anti-angiogenic strategies may play a role in salvage therapy for this tumor.