APLN-APLNR signaling controls tumor angiogenesis and glioblastoma cell invasion

Das Glioblastoma multiforme (GBM) ist ein tödlicher Tumor, der 2,5 Personen von 100000 Erwachsenen pro Jahr betrifft. Trotz der aggressiven Interventionen hat ein Patient eine Lebenserwartung von 14-16 Monaten. Die GBM-Zellen dringen in das Tumorparenchym ein und breiten sich von der ursprünglichen Masse zu entfernten Stellen aus. Der wachsende Tumor induziert das Aussprossen der vorhandenen Blutgefäße und die vaskuläre Proliferation, die als das Phänomen der "Tumorangiogenese“ bekannt ist. Angesichts der ausgeprägten Vaskularisierung des Glioblastoms stellen antiangiogene Wirkstoffe eine vielversprechende therapeutische Strategie dar und viele Medikamente werden derzeit untersucht, um diese Malignität zu behandeln. Die meisten Interventionen zielen auf das Vascular Endothelial Growth Factor (VEGF) Signal ab, aber ihre langfristigen Vorteile haben den Erwartungen nicht entsprochen: der Tumor kommt immer wieder, unterstützt von der Hochregulation anderer angiogener Signale und der zusätzlichen Hilfe der Tumor-assoziierten myeloiden Zellen. Deshalb ist die Validierung alternativer Ziele ein drängendes Thema in der präklinischen Forschung, um effizientere Therapien gegen das GBM zu finden. Unter den vielen neuen antiangiogenen Signalen, die an der GBM-Neoangiogenese beteiligt sind, hat die aktuelle Forschung neue Aufmerksamkeit auf den Apelin - Apelin Rezeptor (APLN-APLNR) Signalweg gelenkt. Das APLN-APLNR-Signal spielt eine wichtige Rolle bei der Entwicklung des vaskulären Systems während der Embriogenese, aber auch bei verschiedenen pathologischen Zuständen. In meiner Doktorarbeit habe ich eine ausführliche Charakterisierung der Expression von APLN und APLNR in in vitro Zellkulturen aus GBM-Patienten und in GBM Maus- und menschlichen Proben durchgeführt. Ligand und Rezeptor sind im GBM-Gewebe hochreguliert und diese Hochregulation ist mit dem angiogenen GBM-Phänotyp assoziiert. Die Erzeugung mehrerer primärer GBM-Zellen mit Verlust der APLN-Expression hat dabei die Notwendigkeit des APLN-Signals für die GBM-Neoangiogenese bestätigt. Außerdem, führte der Verlust eines autokrinen APLN-APLNR-Signals in den implantierten GBM-Zellen zu einer erhöhen Tumorinvasion. In verschiedenen humanen GBM-Proben wies die besondere Verteilung von Ligand und Rezeptor in der Tumormasse auf die Doppelrolle dieses Signals sowohl bei der Tumorangiogenese als auch der Tumorzell-Invasion hin. Die invasive Fähigkeit der GBM-Zellen mit APLN-Verlust wurde in vitro umfassend charakterisiert, wobei, analog zu den in vivo Resultaten, das Fehlen eines autokrinen APLN-APLNR-Signals die Zellinvasion antreibt. Zusätzlich fand ich heraus, dass die Blockade von APLNR die Zellinvasion in vitro beeinflusst und dass die intrazelluläre Rezeptorverteilung sich dabei ändert. Daher könnte der Aktivierungsstatus des Rezeptors selbst eine zentrale Funktion bei der Bestimmung des GBM-Zellverhaltens haben. Die zusätzlich hergestellten primären GBM-Zellen mit APLNR-Verlust werden in zukünftigen Studien eine bessere Charakterisierung des APLNR Rezeptors und seiner Rolle als Treiber der Tumorinvasion ermöglichen. Die Analyse verschiedener Proben von Patienten und Mausmodelle, die aus Studien über die Behandlung des GBMs mit antiangiogenen Mitteln kommen, zeigte, dass der APLN-APLNR-Signalweg auch an der Rekurrenz des Tumors beteiligt ist. Des Weiteren konnte ich darlegen, dass die therapeutische Blockade von APLNR in vivo, die die Tumorinvasion und Angiogenese reduzierte, eine erhöhte Akkumulation von intratumoralen myeloiden Zellen auslöst, welche mit der Tumorrekurrenz nach Verabreichung von antiangiogenen Behandlungen verbunden zu sein scheint. Insgesamt, zeigte es sich in meiner Arbeit, dass der APLN-APLNR-Signalweg, mit seiner prominenten Expression in GBM-Gewebe und seiner Rolle bei der Eindämmung der GBM-Invasion und –Angiogenese, ein interessantes Ziel für zukünftige Tumortherapien darstellt. Weitere Studien sind jedoch notwendig, um die Konsequenzen und das therapeutische Potenzial seiner Blockade vollständig zu offenbaren.Glioblastoma multiforme (GBM) is a deadly tumor that affects 2.5 people every 100000 adults per year. Despite the aggressive interventions, a GBM patient has a life expectancy of 14-16 months. GBM cells invade the tumor parenchyma and spread to distant sites from the original mass. The growing tumor induces sprouting of the existing vessels and vascular proliferation, the phenomenon known as “tumor angiogenesis”. Given the prominent vascularization of glioblastoma, anti-angiogenic agents are a promising strategy for the treatment of this malignancy and many drugs are under evaluation. The majority of these interventions, which target the vascular endothelial growth factor (VEGF) signaling pathway, do not show long-term benefits: tumor rebound always occurs, supported by the upregulation of other angiogenic pathways and the tumor-promoting role of the tumor-associated myeloid cells. Therefore, the validation of alternative targets for more efficient therapies is an urgent need in preclinical research. Among other emerging angiogenic pathways involved in GBM neo-angiogenesis, recent findings brought attention to the apelin-apelin receptor (APLN-APLNR) signaling, which has a primary role in the development of the vascular system during embryogenesis, but it is also associated to different pathological conditions. In the present thesis, I performed an extensive characterization of the expression of APLN and APLNR in in vitro cultures of patient-derived GBM cells and in mouse and human GBM specimens. Ligand and receptor were up-regulated in the GBM tissue and this upregulation was associated with the GBM angiogenic phenotype. The generation of several primary GBM cells with loss of APLN expression confirmed that GBM neo-angiogenesis in vivo depends on APLN function. Moreover, the loss of an autocrine APLN-APLNR signaling in the implanted GBM cells drove tumor invasion. In various human GBM samples, the peculiar distribution of both ligand and receptor across the tumor mass hinted to the dual role of the pathway in tumor angiogenesis and invasion. The invasive ability of the GBM cells with loss of APLN was extensively characterized in vitro, where, as demonstrated in vivo, the absence of an autocrine APLN-APLNR signaling increased cell invasion. In addition, the in vivo intratumoral administration of the receptor antagonist apelin-F13A was able to reduce tumor invasion and angiogenesis. In vitro, the exposure to apelin-F13A reduced the invasive abilities of the cells tested. Moreover, the administration of apelin-13 and apelin-F13A did not only modify the in vitro and in vivo behavior of the GBM cells, but also the intracellular distribution of APLNR. Therefore, the distribution/activation status of the receptor itself may have a central function in the determination of the GBM phenotype. Next, the analysis of various samples obtained from different studies of GBMs therapeutically-treated with anti-angiogenic agents, demonstrated that the APLN-APLNR signaling, aside from being a driver of tumor progression, may also be involved in therapy resistance. Overall, the prominent expression of the APLN-APLNR signaling in GBM tissue and its role in driving GBM invasion and angiogenesis indicate its promising function as target of future tumor therapies. Further studies, however, are required to fully disclose the consequences and the therapeutic potential of its blockade

APLN-APLNR signaling controls tumor angiogenesis and glioblastoma cell invasion

Das Glioblastoma multiforme (GBM) ist ein tödlicher Tumor, der 2,5 Personen von 100000 Erwachsenen pro Jahr betrifft. Trotz der aggressiven Interventionen hat ein Patient eine Lebenserwartung von 14-16 Monaten. Die GBM-Zellen dringen in das Tumorparenchym ein und breiten sich von der ursprünglichen Masse zu entfernten Stellen aus. Der wachsende Tumor induziert das Aussprossen der vorhandenen Blutgefäße und die vaskuläre Proliferation, die als das Phänomen der "Tumorangiogenese“ bekannt ist. Angesichts der ausgeprägten Vaskularisierung des Glioblastoms stellen antiangiogene Wirkstoffe eine vielversprechende therapeutische Strategie dar und viele Medikamente werden derzeit untersucht, um diese Malignität zu behandeln. Die meisten Interventionen zielen auf das Vascular Endothelial Growth Factor (VEGF) Signal ab, aber ihre langfristigen Vorteile haben den Erwartungen nicht entsprochen: der Tumor kommt immer wieder, unterstützt von der Hochregulation anderer angiogener Signale und der zusätzlichen Hilfe der Tumor-assoziierten myeloiden Zellen. Deshalb ist die Validierung alternativer Ziele ein drängendes Thema in der präklinischen Forschung, um effizientere Therapien gegen das GBM zu finden. Unter den vielen neuen antiangiogenen Signalen, die an der GBM-Neoangiogenese beteiligt sind, hat die aktuelle Forschung neue Aufmerksamkeit auf den Apelin - Apelin Rezeptor (APLN-APLNR) Signalweg gelenkt. Das APLN-APLNR-Signal spielt eine wichtige Rolle bei der Entwicklung des vaskulären Systems während der Embriogenese, aber auch bei verschiedenen pathologischen Zuständen. In meiner Doktorarbeit habe ich eine ausführliche Charakterisierung der Expression von APLN und APLNR in in vitro Zellkulturen aus GBM-Patienten und in GBM Maus- und menschlichen Proben durchgeführt. Ligand und Rezeptor sind im GBM-Gewebe hochreguliert und diese Hochregulation ist mit dem angiogenen GBM-Phänotyp assoziiert. Die Erzeugung mehrerer primärer GBM-Zellen mit Verlust der APLN-Expression hat dabei die Notwendigkeit des APLN-Signals für die GBM-Neoangiogenese bestätigt. Außerdem, führte der Verlust eines autokrinen APLN-APLNR-Signals in den implantierten GBM-Zellen zu einer erhöhen Tumorinvasion. In verschiedenen humanen GBM-Proben wies die besondere Verteilung von Ligand und Rezeptor in der Tumormasse auf die Doppelrolle dieses Signals sowohl bei der Tumorangiogenese als auch der Tumorzell-Invasion hin. Die invasive Fähigkeit der GBM-Zellen mit APLN-Verlust wurde in vitro umfassend charakterisiert, wobei, analog zu den in vivo Resultaten, das Fehlen eines autokrinen APLN-APLNR-Signals die Zellinvasion antreibt. Zusätzlich fand ich heraus, dass die Blockade von APLNR die Zellinvasion in vitro beeinflusst und dass die intrazelluläre Rezeptorverteilung sich dabei ändert. Daher könnte der Aktivierungsstatus des Rezeptors selbst eine zentrale Funktion bei der Bestimmung des GBM-Zellverhaltens haben. Die zusätzlich hergestellten primären GBM-Zellen mit APLNR-Verlust werden in zukünftigen Studien eine bessere Charakterisierung des APLNR Rezeptors und seiner Rolle als Treiber der Tumorinvasion ermöglichen. Die Analyse verschiedener Proben von Patienten und Mausmodelle, die aus Studien über die Behandlung des GBMs mit antiangiogenen Mitteln kommen, zeigte, dass der APLN-APLNR-Signalweg auch an der Rekurrenz des Tumors beteiligt ist. Des Weiteren konnte ich darlegen, dass die therapeutische Blockade von APLNR in vivo, die die Tumorinvasion und Angiogenese reduzierte, eine erhöhte Akkumulation von intratumoralen myeloiden Zellen auslöst, welche mit der Tumorrekurrenz nach Verabreichung von antiangiogenen Behandlungen verbunden zu sein scheint. Insgesamt, zeigte es sich in meiner Arbeit, dass der APLN-APLNR-Signalweg, mit seiner prominenten Expression in GBM-Gewebe und seiner Rolle bei der Eindämmung der GBM-Invasion und –Angiogenese, ein interessantes Ziel für zukünftige Tumortherapien darstellt. Weitere Studien sind jedoch notwendig, um die Konsequenzen und das therapeutische Potenzial seiner Blockade vollständig zu offenbaren.Glioblastoma multiforme (GBM) is a deadly tumor that affects 2.5 people every 100000 adults per year. Despite the aggressive interventions, a GBM patient has a life expectancy of 14-16 months. GBM cells invade the tumor parenchyma and spread to distant sites from the original mass. The growing tumor induces sprouting of the existing vessels and vascular proliferation, the phenomenon known as “tumor angiogenesis”. Given the prominent vascularization of glioblastoma, anti-angiogenic agents are a promising strategy for the treatment of this malignancy and many drugs are under evaluation. The majority of these interventions, which target the vascular endothelial growth factor (VEGF) signaling pathway, do not show long-term benefits: tumor rebound always occurs, supported by the upregulation of other angiogenic pathways and the tumor-promoting role of the tumor-associated myeloid cells. Therefore, the validation of alternative targets for more efficient therapies is an urgent need in preclinical research. Among other emerging angiogenic pathways involved in GBM neo-angiogenesis, recent findings brought attention to the apelin-apelin receptor (APLN-APLNR) signaling, which has a primary role in the development of the vascular system during embryogenesis, but it is also associated to different pathological conditions. In the present thesis, I performed an extensive characterization of the expression of APLN and APLNR in in vitro cultures of patient-derived GBM cells and in mouse and human GBM specimens. Ligand and receptor were up-regulated in the GBM tissue and this upregulation was associated with the GBM angiogenic phenotype. The generation of several primary GBM cells with loss of APLN expression confirmed that GBM neo-angiogenesis in vivo depends on APLN function. Moreover, the loss of an autocrine APLN-APLNR signaling in the implanted GBM cells drove tumor invasion. In various human GBM samples, the peculiar distribution of both ligand and receptor across the tumor mass hinted to the dual role of the pathway in tumor angiogenesis and invasion. The invasive ability of the GBM cells with loss of APLN was extensively characterized in vitro, where, as demonstrated in vivo, the absence of an autocrine APLN-APLNR signaling increased cell invasion. In addition, the in vivo intratumoral administration of the receptor antagonist apelin-F13A was able to reduce tumor invasion and angiogenesis. In vitro, the exposure to apelin-F13A reduced the invasive abilities of the cells tested. Moreover, the administration of apelin-13 and apelin-F13A did not only modify the in vitro and in vivo behavior of the GBM cells, but also the intracellular distribution of APLNR. Therefore, the distribution/activation status of the receptor itself may have a central function in the determination of the GBM phenotype. Next, the analysis of various samples obtained from different studies of GBMs therapeutically-treated with anti-angiogenic agents, demonstrated that the APLN-APLNR signaling, aside from being a driver of tumor progression, may also be involved in therapy resistance. Overall, the prominent expression of the APLN-APLNR signaling in GBM tissue and its role in driving GBM invasion and angiogenesis indicate its promising function as target of future tumor therapies. Further studies, however, are required to fully disclose the consequences and the therapeutic potential of its blockade

Monitoring of Tumor Growth with [F-18]-FET PET in a Mouse Model of Glioblastoma: SUV Measurements and Volumetric Approaches

Noninvasive tumor growth monitoring is of particular interest for the evaluation of experimental glioma therapies. This study investigates the potential of positron emission tomography (PET) using O-(2-F-18-fluoroethyl)-L-tyrosine ([F-18]-FET) to determine tumor growth in a murine glioblastoma (GBM) model including estimation of the biological tumor volume (BTV), which has hitherto not been investigated in the pre-clinical context. Fifteen GBM bearing mice (GL261) and six control mice (shams) were investigated during 5 weeks by PET followed by autoradiographic and histological assessments. [F-18]-FET PET was quantitated by calculation of maximum and mean standardized uptake values within a universal volume-of-interest (VOI) corrected for healthy background (SUVmax/BG, SUVmean/BG). A partial volume effect correction (PVEC) was applied in comparison to ex vivo autoradiography. BTVs obtained by predefined thresholds for VOI definition (SUV/BG: >= 1.4;>= 1.6;>= 1.8;>= 2.0) were compared to the histologically assessed tumor volume (n = 8). Finally, individual-optimal" thresholds for BTV definition best reflecting the histology were determined. In GBM mice SUVmax/BG and SUVmean/BG clearly increased with time, however at high inter-animal variability. No relevant [F-18]-FET uptake was observed in shams. PVEC recovered signal loss of SUVmean/BG assessment in relation to autoradiography. BTV as estimated by predefined thresholds strongly differed from the histology volume. Strikingly, the individual "optimal" thresholds for BTV assessment correlated highly with SUVmax/BG (rho = 0.97, p < 0.001), allowing SUVmax/BG-based calculation of individual thresholds. The method was verified by a subsequent validation study (n = 15, p = 0.88, p < 0.01) leading to extensively higher agreement of BTV estimations when compared to histology in contrast to predefined thresholds. [F-18]-FET PET with standard SUV measurements is feasible for glioma imaging in the GBM mouse model. PVEC is beneficial to improve accuracy of [F-18]-FET PET SUV quantification. Although SUVmax/BG and SUVmean/BG increase during the disease course, these parameters do not correlate with the respective tumor size. For the first time, we propose a histology-verified method allowing appropriate individual BTV estimation for volumetric in vivo monitoring of tumor growth with [F-18]-FET PET and show that standardized thresholds from routine clinical practice seem to be inappropriate for BTV estimation in the GBM mouse model

Decreased demand for olfactory periglomerular cells impacts on neural precursor cell viability in the rostral migratory stream

The subventricular zone (SVZ) provides a constant supply of new neurons to the olfactory bulb (OB). Different studies have investigated the role of olfactory sensory input to neural precursor cell (NPC) turnover in the SVZ but it was not addressed if a reduced demand specifically for periglomerular neurons impacts on NPC-traits in the rostral migratory stream (RMS). We here report that membrane type-1 matrix metalloproteinase (MT1-MMP) deficient mice have reduced complexity of the nasal turbinates, decreased sensory innervation of the OB, reduced numbers of olfactory glomeruli and reduced OB-size without alterations in SVZ neurogenesis. Large parts of the RMS were fully preserved in MT1-MMP-deficient mice, but we detected an increase in cell death-levels and a decrease in SVZ-derived neuroblasts in the distal RMS, as compared to controls. BrdU-tracking experiments showed that homing of NPCs specifically to the glomerular layer was reduced in MT1-MMP-deficient mice in contrast to controls while numbers of tracked cells remained equal in other OB-layers throughout all experimental groups. Altogether, our data show the demand for olfactory interneurons in the glomerular layer modulates cell turnover in the RMS, but has no impact on subventricular neurogenesis

Long-term effects of an acute and systemic administration of LPS on adult neurogenesis and spatial memory

The cognitive reserve is the capacity of the brain to maintain normal performance while exposed to insults or ageing. Increasing evidences point to a role for the interaction between inflammatory conditions and cognitive reserve status during Alzheimer's disease (AD) progression. The production of new neurons along adult life can be considered as one of the components of the cognitive reserve. Interestingly, adult neurogenesis is decreased in mouse models of AD and following inflammatory processes. The aim of this work is to reveal the long-term impact of a systemic inflammatory event on memory and adult neurogenesis in wild type (WT) and triple transgenic mouse model of AD (3xTg-AD). Four month-old mice were intraperitoneally injected once with saline or lipopolysaccharide (LPS) and their performance on spatial memory analyzed with the Morris water maze (MWM) test 7 weeks later. Our data showed that a single intraperitoneal injection with LPS has a long-term impact in the production of hippocampal neurons. Consistently, LPS-treated WT mice showed less doublecortin-positive neurons, less synaptic contacts in newborn neurons, and decreased dendritic volume and complexity. These surprising observations were accompanied with memory deficits. 3xTg-AD mice showed a decrease in new neurons in the dentate gyrus compatible with, although exacerbated, the pattern observed in WT LPS-treated mice. In 3xTg-AD mice, LPS injection did not significantly affected the production of new neurons but reduced their number of synaptic puncta and impaired memory performance, when compared to the observations made in saline-treated 3xTg-AD mice. These data indicate that LPS treatment induces a long-term impairment on hippocampal neurogenesis and memory. Our results show that acute neuroinflammatory events influence the production of new hippocampal neurons, affecting the cognitive reserve and leading to the development of memory deficits associated to AD pathology

Chronic hyperglycemia impairs hippocampal neurogenesis and memory in an Alzheimer’s disease mouse model

During aging, lifestyle-related factors shape the brain's response to insults and modulate the progression of neurodegenerative pathologies such as Alzheimer's disease (AD). This is the case for chronic hyperglycemia associated with type 2 diabetes, which reduces the brain's ability to handle the neurodegenerative burden associated with AD. However, the mechanisms behind the effects of chronic hyperglycemia in the context of AD are not fully understood. Here, we show that newly generated neurons in the hippocampal dentate gyrus of triple transgenic AD (3xTg-AD) mice present increased dendritic arborization and a number of synaptic puncta, which may constitute a compensatory mechanism allowing the animals to cope with a lower neurogenesis rate. Contrariwise, chronic hyperglycemia decreases the complexity and differentiation of 3xTg-AD newborn neurons and reduces the levels of β-catenin, a key intrinsic modulator of neuronal maturation. Moreover, synaptic facilitation is depressed in hyperglycemic 3xTg-AD mice, accompanying the defective hippocampal-dependent memory. Our data suggest that hyperglycemia evokes cellular and functional alterations that accelerate the onset of AD-related symptoms, namely memory impairment. •Hyperglycemia reduces adult hippocampal neurogenesis in an Alzheimer's disease model.•Hyperglycemia decreases the complexity of 3xTg-AD hippocampal immature neurons.•Hyperglycemia reduces β-catenin levels in 3xTg-AD hippocampal new neurons.•Hyperglycemia affects dentate gyrus long-term synaptic plasticity in 3xTg-AD mice.•Spatial memory impairment is exacerbated in hyperglycemic 3xTg-AD mice

Targeting APLN/APLNR improves antiangiogenic efficiency and blunts proinvasive side effects of VEGFA/VEGFR2 blockade in glioblastoma

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.acceptedVersio

Targeting APLN/APLNR improves antiangiogenic efficiency and blunts proinvasive side effects of VEGFA/VEGFR2 blockade in glioblastoma

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