Autocrine VEGFR1 and VEGFR2 signaling promotes survival in human glioblastoma models in vitro and in vivo

Abstract

BackgroundAlthough the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) system has become a prime target for antiangiogenic treatment, its biological role in glioblastoma beyond angiogenesis has remained controversial.MethodsUsing neutralizing antibodies to VEGF or placental growth factor (PlGF) or the tyrosine kinase inhibitor, cediranib, or lentiviral gene silencing, we delineated autocrine signaling in glioma cell lines. The in vivo effects of VEGFR1 and VEGFR2 depletion were evaluated in orthotopic glioma xenograft models.ResultsVEGFR1 and VEGFR2 modulated glioma cell clonogenicity, viability, and invasiveness in vitro in an autocrine, cell–line-specific manner. VEGFR1 silencing promoted mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling, whereas VEGFR2 silencing resulted in cell-type dependent activation of the protein kinase B (PKB)/AKT and MAPK/ERK pathways. These responses may represent specific escape mechanisms from VEGFR inhibition. The survival of orthotopic glioma-bearing mice was prolonged upon VEGFR1 silencing in the LNT-229, LN-308, and U87MG models and upon VEGFR2 silencing in LN-308 and U87MG. Disruption of VEGFR1 and VEGFR2 signaling was associated with decreased tumor size, increased tumor necrosis, or loss of matrix metalloproteinase 9 (MMP9) immunoreactivity. Neutralizing VEGF and PlGF by specific antibodies was superior to either antibody treatment alone in the VEGFR1-dependent LNT-229 model.ConclusionsDifferential dependence on autocrine signaling through VEGFR1 and VEGFR2 suggests a need for biomarker–stratified VEGF(R)-based therapeutic approaches to glioblastoma.

Perivascular signals alter global gene expression profile of glioblastoma and response to temozolomide in a gelatin hydrogel

“…http://dx.doi.org/10.1101/273763 doi: bioRxiv preprint first posted online Mar. 3, 2018; using in vivo models and patient samples [20,33,63,[70][71][72]. Differential gene expression analysis also demonstrated upregulation of several genes previously linked to GBM malignancy, such as the matrix metalloproteinases, PDGFB and PDGF receptors, TNC, FN1, and EGFR, consistent with previous findings using conventional cell culture and analysis of patient and xenograft-derived tumor specimens [54,61,[73][74][75].…”

Antitumor Activity of DLX1008, an Anti-VEGFA Antibody Fragment with Low Picomolar Affinity, in Human Glioma Models

“…Cells were washed and serum-starved in the presence of equimolar concentrations (2683 nM) of DLX1008 or control scFv DLX1084 for 8 hours. A high concentration of VEGF is generally needed for VEGFR stimulation in glioma cells (Szabo et al, 2016). Therefore, a large amount of antibody is needed for neutralization, and the highest feasible concentration was used.…”

“…Twice-weekly intraperitoneal injection of 5 mg/kg per day of bevacizumab was included as a reference in some experiments. The mean size of the intracranial tumors was estimated at the level of the largest tumor area of H&Estained sections (Szabo et al, 2016).…”

“…VEGF is a growth factor that plays a key role in angiogenesis. Along with its stimulatory activity on tumor vessel formation, VEGF may exert tumor-intrinsic survival properties mediated by both VEGF receptors 1 and 2 (Knizetova et al, 2008;von Baumgarten et al, 2011;Lu et al, 2012;Szabo et al, 2016).…”

SWAP70 undergoes dynamic conformational regulation at the leading edge of migrating cells

“…SWAP70 undergoes conformational regulation at the leading edge of migratory U87MG cells U87MG glioma cells are PTEN null, display several autocrine growth factor signalling loops and are highly motile [30][31][32][33]. When SWAP70-R was expressed in these motile cells, approximately half of the cells showed some focal peripheral enrichment of the reporter, often in lamellipodia at the migratory leading edge (Fig.…”