Systemic anti-vascular endothelial growth factor therapies induce a painful sensory neuropathy.

Systemic vascular endothelial growth factor inhibition, in combination with chemotherapy, improves the outcome of patients with metastatic cancer. Peripheral sensory neuropathies occurring in patients receiving both drugs are attributed to the chemotherapy. Here, we provide unprecedented evidence that vascular endothelial growth factor receptor inhibitors trigger a painful neuropathy and aggravate paclitaxel-induced neuropathies in mice. By using transgenic mice with altered neuronal vascular endothelial growth factor receptor expression, systemic inhibition of vascular endothelial growth factor receptors was shown to interfere with the endogenous neuroprotective activities of vascular endothelial growth factor on sensory neurons. In vitro, vascular endothelial growth factor prevented primary dorsal root ganglion cultures from paclitaxel-induced neuronal stress and cell death by counteracting mitochondrial membrane potential decreases and normalizing hyperacetylation of α-tubulin. In contrast, vascular endothelial growth factor receptor inhibitors exerted opposite effects. Intriguingly, vascular endothelial growth factor or vascular endothelial growth factor receptor inhibitors exerted their effects through a mechanism whereby Hdac6, through Hsp90, controls vascular endothelial growth factor receptor-2-mediated expression of the anti-apoptotic Bcl2. Our observations that systemic anti-vascular endothelial growth factor therapies interfere with the neuroprotective activities of vascular endothelial growth factor may have important implications for the application of anti-vascular endothelial growth factor therapies in cancer patients.

Neuronal FLT1 receptor and its selective ligand VEGF-B protect against retrograde degeneration of sensory neurons.

Even though VEGF-B is a homologue of the potent angiogenic factor VEGF, its angiogenic activities have been controversial. Intrigued by findings that VEGF-B may also affect neuronal cells, we assessed the neuroprotective and vasculoprotective effects of VEGF-B in the skin, in which vessels and nerves are functionally intertwined. Although VEGF-B and its FLT1 receptor were prominently expressed in dorsal root ganglion (DRG) neurons innervating the hindlimb skin, they were not essential for nerve function or vascularization of the skin. However, primary DRG cultures lacking VEGF-B or FLT1 exhibited increased neuronal stress and were more susceptible to paclitaxel-induced cell death. Concomitantly, mice lacking VEGF-B or a functional FLT1 developed more retrograde degeneration of sensory neurons in a model of distal neuropathy. On the other hand, the addition of the VEGF-B isoform, VEGF-B(186), to DRG cultures antagonized neuronal stress, maintained the mitochondrial membrane potential and stimulated neuronal survival. Mice overexpressing VEGF-B(186) or FLT1 selectively in neurons were protected against the distal neuropathy, whereas exogenous VEGF-B(186), either delivered by gene transfer or as a recombinant factor, was protective by directly affecting sensory neurons and not the surrounding vasculature. Overall, this indicates that VEGF-B, instead of acting as an angiogenic factor, exerts direct neuroprotective effects through FLT1. These findings also suggest a clinically relevant role for VEGF-B in preventing distal neuropathies.

Matrix-binding vascular endothelial growth factor (VEGF) isoforms guide granule cell migration in the cerebellum via VEGF receptor Flk1.

Vascular endothelial growth factor (VEGF) regulates angiogenesis, but also has important, yet poorly characterized roles in neuronal wiring. Using several genetic and in vitro approaches, we discovered a novel role for VEGF in the control of cerebellar granule cell (GC) migration from the external granule cell layer (EGL) toward the Purkinje cell layer (PCL). GCs express the VEGF receptor Flk1, and are chemoattracted by VEGF, whose levels are higher in the PCL than EGL. Lowering VEGF levels in mice in vivo or ectopic VEGF expression in the EGL ex vivo perturbs GC migration. Using GC-specific Flk1 knock-out mice, we provide for the first time in vivo evidence for a direct chemoattractive effect of VEGF on neurons via Flk1 signaling. Finally, using knock-in mice expressing single VEGF isoforms, we show that pericellular deposition of matrix-bound VEGF isoforms around PC dendrites is necessary for proper GC migration in vivo. These findings identify a previously unknown role for VEGF in neuronal migration.

Novel role for vascular endothelial growth factor (VEGF) receptor-1 and its ligand VEGF-B in motor neuron degeneration.

Although vascular endothelial growth factor-B (VEGF-B) is a homolog of the angiogenic factor VEGF, it has only minimal angiogenic activity, raising the question of whether this factor has other (more relevant) biological properties. Intrigued by the possibility that VEGF family members affect neuronal cells, we explored whether VEGF-B might have a role in the nervous system. Here, we document that the 60 kDa VEGF-B isoform, VEGF-B(186), is a neuroprotective factor. VEGF-B(186) protected cultured primary motor neurons against degeneration. Mice lacking VEGF-B also developed a more severe form of motor neuron degeneration when intercrossed with mutant SOD1 mice. The in vitro and in vivo effects of VEGF-B(186) were dependent on the tyrosine kinase activities of its receptor, Flt1, in motor neurons. When delivered intracerebroventricularly, VEGF-B(186) prolonged the survival of mutant SOD1 rats. Compared with a similar dose of VEGF, VEGF-B(186) was safer and did not cause vessel growth or blood-brain barrier leakiness. The neuroprotective activity of VEGF-B, in combination with its negligible angiogenic/permeability activity, offers attractive opportunities for the treatment of neurodegenerative diseases.

RIVA - a phase IIa study of rituximab and varlilumab in relapsed or refractory B-cell malignancies: study protocol for a randomized controlled trial.

BACKGROUND: Over 12,000 new cases of B-cell malignancies are diagnosed in the UK each year, with diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) being the most common subtypes. Standard frontline therapy consists of immunochemotherapy with a CD20 monoclonal antibody (mAb), such as rituximab, delivered in combination with multi-agent chemotherapy. Despite being considered a treatable and potentially curable cancer, approximately 30% of DLBCL cases will relapse after frontline therapy. Advanced stage FL is incurable and typically has a relapsing and remitting course with a frequent need for re-treatment. Based on supportive preclinical data, we hypothesised that the addition of varlilumab (an anti-CD27 mAb) to rituximab (an anti-CD20 mAb) can improve the rate, depth and duration of the response of rituximab monotherapy in patients with relapsed or refractory B-cell malignancies. METHODS/DESIGN: Combination treatment of varlilumab plus rituximab, in two different dosing regimens, is being tested in the RIVA trial. RIVA is a two-stage open-label randomised phase IIa design in up to 40 patients with low- or high-grade relapsed or refractory CD20+ B-cell lymphoma. The study is open to recruitment in the UK. Enrolled patients are randomised 1:1 to two different experimental varlilumab to rituximab combinations. The primary objective is to determine the safety and tolerability of the combination and the anti-tumour activity (response) in relapsed or refractory B-cell malignancies. Secondary objectives will include an evaluation of the duration of the response and overall survival. Tertiary translational objectives include assessment of B-cell depletion, changes in immune effector cell populations, expression of CD27 as a biomarker of response and pharmacokinetic properties. Analyses will not be powered for formal statistical comparisons between treatment arms. DISCUSSION: RIVA will determine whether the combination of rituximab and varlilumab in relapsed or refractory B-cell malignancies is active and safe prior to future phase II/III trials. TRIAL REGISTRATION: EudraCT, 2017-000302-37. Registered on 16 January 2017. ISRCTN, ISRCTN15025004 . Registered on 16 August 2017.

VEGF receptor-2 (Flk-1) overexpression in mice counteracts focal epileptic seizures.

Vascular endothelial growth factor (VEGF) was first described as an angiogenic agent, but has recently also been shown to exert various neurotrophic and neuroprotective effects in the nervous system. These effects of VEGF are mainly mediated by its receptor, VEGFR-2, which is also referred to as the fetal liver kinase receptor 1 (Flk-1). VEGF is up-regulated in neurons and glial cells after epileptic seizures and counteracts seizure-induced neurodegeneration. In vitro, VEGF administration suppresses ictal and interictal epileptiform activity caused by AP4 and 0 Mg(2+) via Flk-1 receptor. We therefore explored whether increased VEGF signaling through Flk-1 overexpression may regulate epileptogenesis and ictogenesis in vivo. To this extent, we used transgenic mice overexpressing Flk-1 postnatally in neurons. Intriguingly, Flk-1 overexpressing mice were characterized by an elevated threshold for seizure induction and a decreased duration of focal afterdischarges, indicating anti-ictal action. On the other hand, the kindling progression in these mice was similar to wild-type controls. No significant effects on blood vessels or glia cells, as assessed by Glut1 and GFAP immunohistochemistry, were detected. These results suggest that increased VEGF signaling via overexpression of Flk-1 receptors may directly affect seizure activity even without altering angiogenesis. Thus, Flk-1 could be considered as a novel target for developing future gene therapy strategies against ictal epileptic activity.

VEGF protects motor neurons against excitotoxicity by upregulation of GluR2.

Influx of Ca(2+) ions through the α-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA) receptors is toxic to neurons and contributes to motor neuron degeneration observed in amyotrophic lateral sclerosis (ALS). The Ca(2+) permeability of the AMPA receptor depends on its subunit composition. If the GluR2 subunit is present in the receptor complex, the AMPA receptor is impermeable to Ca(2+). In this study, we identified vascular endothelial growth factor-A (VEGF) as a GluR2 inducing molecule. Cultured motor neurons pretreated with VEGF displayed higher GluR2 levels. This resulted in AMPA receptor currents with a low relative Ca(2+) permeability and in motor neurons that were less vulnerable to AMPA receptor-mediated excitotoxicity. This effect of VEGF was mediated through the VEGFR2 present on the motor neurons and was due to stimulation of GluR2 transcription. Intracerebroventricular treatment with VEGF similarly induced GluR2 expression in the ventral spinal cord of rats and this mechanism contributes to the protective effect of VEGF on motor neurons.

Microglial upregulation of progranulin as a marker of motor neuron degeneration.

Frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) are overlapping neurodegenerative disorders. Mutations in the growth factor progranulin (PGRN) gene cause FTLD, sometimes in conjunction with ALS; such mutations are also observed in some ALS patients. Most PGRN mutations underlying FTLD are null mutations that result in reduced PGRN levels. We investigated PGRN expression in human ALS and in mouse models of motor neuron degeneration. Progranulin plasma or CSF levels in newly diagnosed ALS patients did not differ from those in healthy or disease controls (PGRN mutation-negative FTLD and Alzheimer disease patients). In the mutant SOD1 mouse model of ALS, spinal cord PGRN levels were normal in presymptomatic animals but increased during the degenerative process. This increase in PGRN correlated with enhanced expression of PGRN in microglia. In CSF, PGRN levels were normal in presymptomatic and early symptomatic animals, but with disease progression, a raise in PGRN was detectable. These data indicate that upregulation of PGRN is a marker of the microglial response that occurs with progression in motor neuron diseases.