Ablation of neuropilin 1 from glioma-associated microglia and macrophages slows tumor progression

Gliomas are the most commonly diagnosed primary tumors of the central nervous system (CNS). Median times of survival are dismal regardless of the treatment approach, underlying the need to develop more effective therapies. Modulation of the immune system is a promising strategy as innate and adaptive immunity play important roles in cancer progression. Glioma associated microglia and macrophages (GAMs) can comprise over 30% of the cells in glioma biopsies. Gliomas secrete cytokines that suppress the anti-tumorigenic properties of GAMs, causing them to secrete factors that support the tumor's spread and growth. Neuropilin 1 (Nrp1) is a transmembrane receptor that in mice both amplifies pro-angiogenic signaling in the tumor microenvironment and affects behavior of innate immune cells. Using a Cre-lox system, we generated mice that lack expression of Nrp1 in GAMs. We demonstrate, using an in vivo orthotopic glioma model, that tumors in mice with Nrp1-deficient GAMs exhibit less vascularity, grow at a slower pace, and are populated by increased numbers of anti-tumorigenic GAMs. Moreover, glioma survival times in mice with Nrp1-deficient GAMs were significantly longer. Treating wild-type mice with a small molecule inhibitor of Nrp1's b1 domain, EG00229, which we show here is selective for Nrp1 over Nrp2, yielded an identical outcome. Nrp1-deficient or EG00229-treated wild-type microglia exhibited a shift towards anti-tumorigenicity as evident by altered inflammatory marker profiles in vivo and decreased SMAD2/3 activation when conditioned in the presence of glioma-derived factors. These results provide support for the proposal that pharmacological inhibition of Nrp1 constitutes a potential strategy for suppressing glioma progression

Quark Coalescence for Charmed Mesons in Ultrarelativistic Heavy-Ion Collisions

We investigate effects of charm-quark interactions in a Quark-Gluon Plasma on the production of $D$ and $J/\psi$ mesons in high-energy heavy-ion collisions. Employing a previously constructed coalescence model that successfully reproduces the transverse momentum ($p_T$) spectra and elliptic flow ($v_2(p_T)$) of light hadrons at RHIC from underlying light-quark distributions at the phase transition temperature $T_c$, $D$-meson and $J/\psi$ $p_T$ spectra are evaluated. For the charm-quark distributions, we consider two limiting scenarios: (i) {\em no} rescattering, corresponding to perturbative QCD spectra and (ii) {\em complete} thermalization including transverse expansion. With the $D$-meson spectra acquiring a minimal $v_2$ inherited from their light-quark content, the corresponding semileptonic decay spectra of single electrons are found to practically preserve the $v_2$ of the parent particles, exhibiting marked differences between the pQCD and thermal scenarios for $p_T\ge 1$ GeV. Likewise, the $p_T$-spectra and yields of $J/\psi$'s differ appreciably in the two scenarios.Comment: 6 pages, 4 figures, version published in PLB with updated figure

Peptides Derived from Vascular Endothelial Growth Factor B Show Potent Binding to Neuropilin-1

Vascular endothelial growth factors (VEGFs) regulate significant pathways in angiogenesis, myocardial and neuronal protection, metabolism, and cancer progression. The VEGF-B isoform is involved in cell survival, anti-apoptotic and antioxidant mechanisms, through binding to VEGF receptor 1 and neuropilin-1 (NRP-1). We employed surface plasmon resonance technology and X-ray crystallography to analyse the molecular basis of the interaction between VEGF-B and the b1 domain of NRP-1, and developed VEGF-B - C-terminus derived peptides to be used as chemical tools for studying VEGF-B - NRP-1 related pathways. Peptide lipidation was used as a means to stabilise the peptides. VEGF-B - derived peptides containing a C-terminal arginine show potent binding to NRP1-b1. Peptide lipidation increased binding residence time and improved plasma stability. A crystal structure of a peptide with NRP-1 demonstrated that VEGF-B peptides bind at the canonical C-terminal Arginine binding site. VEGF-B C-terminus imparts higher affinity for NRP-1 than the corresponding VEGF-A_{165} region. This tight binding may impact on the activity and selectivity of the full-length protein. The VEGF-B_{167} derived peptides were more effective than VEGF-A_{165} peptides in blocking functional phosphorylation events. Blockers of VEGF-B function have potential applications in diabetes and non-alcoholic fatty liver disease

N-terminal modification of VEGF-A C terminus-derived peptides delineates structural features involved in neuropilin-1 binding and functional activity

The interaction between VEGF-A and its neuropilin (NRP) receptors mediates a number of important biological effects. NRP1 and the related molecule NRP2 are widely expressed on multiple tumour types and throughout the tumour vasculature, and are emerging as critical molecules required for the progression of angiogenic diseases. Given the increasing evidence supporting a role for NRP1 in tumour development, there is growing interest in developing inhibitors of NRP1 interactions with VEGF and its other ligands. In order to probe the interaction we synthesised a number of exon 7- and 8-derived bicyclic peptides with N-terminal lipophilic groups and found a simple N-octanoyl derivative (EG00086) to be the most potent and functionally active. Detailed modelling studies indicated that new intramolecular hydrogen bonds were formed, stabilising the structure and possibly contributing to the potency. Removal of a salt bridge between D142 and R164 implicated in VEGF-A binding to neuropilin-1 had a minor effect on potency. Isothermal calorimetry was used to assess binding of EG00086 to NRP1 and NRP2, and the stability of the peptide in serum and in vivo was investigated. EG00086 is a potent blocker of VEGF-promoted cellular adhesion to extracellular matrices, and phosphorylation of p130Cas contributes to this effect