Antiangiogenic therapy of glioblastoma (GBM) with bevacizumab, a VEGFA-blocking antibody, may accelerate tumor cell invasion and induce alternative angiogenic pathways. Here we investigate the roles of the proangiogenic apelin receptor APLNR and its cognate ligand apelin in VEGFA/VEGFR2 antiangiogenic therapy against distinct subtypes of GBM. In proneural GBM, apelin levels were downregulated by VEGFA or VEGFR2 blockade. A central role for apelin/APLNR in controlling GBM vascularization was corroborated in a serial implantation model of the angiogenic switch that occurs in human GBM. Apelin and APLNR are broadly expressed in human GBM, and knockdown or knockout of APLN in orthotopic models of proneural or classical GBM subtypes significantly reduced GBM vascularization compared with controls. However, reduction in apelin expression led to accelerated GBM cell invasion. Analysis of stereotactic GBM biopsies from patients as well as from in vitro and in vivo experiments revealed increased dissemination of APLNR-positive tumor cells when apelin levels were reduced. Application of apelin-F13A, a mutant APLNR ligand, blocked tumor angiogenesis and GBM cell invasion. Furthermore, cotargeting VEGFR2 and APLNR synergistically improved survival of mice bearing proneural GBM. In summary, we show that apelin/APLNR signaling controls GBM angiogenesis and invasion and that both pathologic features are blunted by apelin-F13A. We suggest that apelin-F13A can improve the efficiency and reduce the side effects of established antiangiogenic treatments for distinct GBM subtypes.Significance: Pharmacologic targeting of the APLNR acts synergistically with established antiangiogenic treatments in glioblastoma and blunts therapy resistance to current strategies for antiangiogenesis.

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Highlights d Uncovering brain tumor-associated cells with a myeloid expression profile (TAMEP) d TAMEP appear as a myeloid population but do not derive from microglia or bone marrow d TAMEP originate from local progenitors activated by brain tumors d TAMEP promote tumor expansion by enhancing vessel density

Background The transcription factor NFκB drives neoplastic progression of many cancers including primary brain tumors (glioblastoma; GBM). Precise therapeutic modulation of NFκB activity can suppress central oncogenic signalling pathways in GBM, but clinically applicable compounds to achieve this goal have remained elusive. Methods In a pharmacogenomics study with a panel of transgenic glioma cells we observed that NFκB can be converted into a tumor suppressor by the non-psychotropic cannabinoid Cannabidiol (CBD). Subsequently, we investigated the anti-tumor effects of CBD, which is used as an anticonvulsive drug (Epidiolex) in pediatric neurology, in a larger set of human primary GBM stem-like cells (hGSC). For this study we performed pharmacological assays, gene expression profiling, biochemical and cell-biological experiments. We validated our findings using orthotopic in vivo models and bioinformatics analysis of human GBM-datasets. Results We found that CBD promotes DNA binding of the NFκB subunit RELA and simultaneously prevents RELA-phosphorylation on serine-311, a key residue which permits genetic transactivation. Strikingly, sustained DNA binding by RELA lacking phospho-serine 311 was found to mediate hGSC cytotoxicity. Widespread sensitivity to CBD was observed in a cohort of hGSC defined by low levels of reactive oxygen-species (ROS), while high ROS-content in other tumors blocked CBD induced hGSC death. Consequently, ROS levels served as predictive biomarker for CBD-sensitive tumors. Conclusions This evidence demonstrates how a clinically approved drug can convert NFκB into a tumor suppressor and suggests a promising repurposing option for GBM-therapy.

Background and PurposeAlthough bevacizumab (BV) has been approved as second-line therapy for recurrent glioblastoma (GB), the efficacy and safety of BV for patients with newly diagnosed GB remain unclear.Methodology/Principal FindingsWe systematically searched electronic databases (PubMed, EMBASE, OVID, etc.) to identify related studies published from January 1966 and August 2016. Eight randomized controlled trials including a total of 2,185 patients with GB were included. We found that the median progression-free survival (PFS) was higher in the BV group than in the standard therapy (ST) group (pooled hazard ratio, 0.73; 95%CI, 0.62–0.86; P = 0.0001). Compared with ST, BV improved the PFS rate at 6 months (OR 3.33, 95% CI 2.73–4.06, p<0.00001) and 12 months (OR 2.10, 95% CI 1.74–2.54, p<0.00001). There were no significant differences in median overall survival between the BV and ST groups (OR, 1.01; 95%CI, 0.83–1.23; P = 0.95). The BV group had higher survival rates at 6 months (OR, 1.41; 95% CI, 1.09–1.84; P = 0.01) and 12 months (OR, 1.23; 95% CI, 1.02–1.48; P = 0.03), but a low survival rate at the 36-month follow-up (OR, 0.57; 95% CI, 0.32–0.98; P = 0.04). For the incidence of adverse events, three adverse outcomes were found to be significantly different between BV and ST groups, including hypertension (8.37% vs. 1.62%, p<0.000001), proteinuria (7.65% vs. 0%, p<0.001), and fatigue (14.54% vs. 9.01%, p = 0.05).Conclusions/SignificanceOur study indicates that combination of BV with ST for newly diagnosed GB did not improve the median overall survival but result in longer median PFS, maintaining the quality of life and functional status. However, the long-term use of BV is associated with a higher incidence of adverse events and mortality.Study RegistrationThis research was registered at PROSPERO. (Registration Number: CRD42016038247).

Pannexin 2 (Panx2) is a large-pore ATP-permeable channel with critical roles in various physiological processes, such as the inflammatory response, energy production and apoptosis. Its dysfunction is related to numerous pathological conditions including ischemic brain injury, glioma and glioblastoma multiforme. However, the working mechanism of Panx2 remains unclear. Here, we present the cryo-electron microscopy structure of human Panx2 at a resolution of 3.4 Å. Panx2 structure assembles as a heptamer, forming an exceptionally wide channel pore across the transmembrane and intracellular domains, which is compatible with ATP permeation. Comparing Panx2 with Panx1 structures in different states reveals that the Panx2 structure corresponds to an open channel state. A ring of seven arginine residues located at the extracellular entrance forms the narrowest site of the channel, which serves as the critical molecular filter controlling the permeation of substrate molecules. This is further verified by molecular dynamics simulations and ATP release assays. Our studies reveal the architecture of the Panx2 channel and provide insights into the molecular mechanism of its channel gating.

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