Anti-VEGF treatment reduces blood supply and increases tumor cell invasion in glioblastoma

Abstract

Bevacizumab, an antibody against vascular endothelial growth factor (VEGF), is a promising, yet controversial, drug in human glioblastoma treatment (GBM). Its effects on tumor burden, recurrence, and vascular physiology are unclear. We therefore determined the tumor response to bevacizumab at the phenotypic, physiological, and molecular level in a clinically relevant intracranial GBM xenograft model derived from patient tumor spheroids. Using anatomical and physiological magnetic resonance imaging (MRI), we show that bevacizumab causes a strong decrease in contrast enhancement while having only a marginal effect on tumor growth. Interestingly, dynamic contrast-enhanced MRI revealed a significant reduction of the vascular supply, as evidenced by a decrease in intratumoral blood flow and volume and, at the morphological level, by a strong reduction of large-and medium-sized blood vessels. Electron microscopy revealed fewer mitochondria in the treated tumor cells. Importantly, this was accompanied by a 68% increase in infiltrating tumor cells in the brain parenchyma. At the molecular level we observed an increase in lactate and alanine metabolites, together with an induction of hypoxia-inducible factor 1α and an activation of the phosphatidyl-inositol-3-kinase pathway. These data strongly suggest that vascular remodeling induced by anti-VEGF treatment leads to a more hypoxic tumor microenvironment. This favors a metabolic change in the tumor cells toward glycolysis, which leads to enhanced tumor cell invasion into the normal brain. The present work underlines the need to combine anti-angiogenic treatment in GBMs with drugs targeting specific signaling or metabolic pathways linked to the glycolytic phenotype.angiogenesis | glioma | metabolism | perfusion G lioblastomas (GBMs) are highly vascularized brain tumors and are therefore attractive targets for anti-angiogenic therapies (1). In particular, vascular endothelial growth factor (VEGF) has been identified as a critical regulator of angiogenesis, and currently a number of clinical trials targeting the VEGFsignaling pathways are under development (2, 3). Bevacizumab (bev), a humanized anti-VEGF antibody, has shown promising results in exploratory phase II trials of recurrent GBM. Alone or in combination with irinotecan, it is well tolerated and shows a high radiological response rate and possibly an increase in median progression-free survival compared with historical controls (4-7), although no impact on overall survival has been reported (8). However, these results are based on small patient cohorts and, because anti-angiogenic agents directly affect vessel permeability, the imaging response assessment based on contrast enhancement (CE) is highly ambiguous (9). Indeed, a direct antitumor effect of bev has remained elusive and the infiltrative part of the tumor may even increase (10,11). In addition to a lack of robust clinical data, the cellular and molecular consequences of anti-VEGF treatment have not been outlined (12). Detailed information on how bev affects ...

Improved Treatment Efficacy of Antiangiogenic Therapy when Combined with Picornavirus Vaccination in the GL261 Glioma Model

“…However, histological analysis revealed a pattern of increased infiltration, with the formation of numerous satellite tumors [29]. These results were consistently reproduced in orthotopic mouse models, where xenografted human gliomas displayed inhibited tumor growth but significantly increased migration of tumor cells into the brain parenchyma and satellite tumor development [27,[30][31][32].…”

“…The GL261-Quad cell line is engineered to express the model antigens human gp100 [25][26][27][28][29][30][31][32][33] , chicken OVA 257-264 , chicken OVA [323][324][325][326][327][328][329][330][331][332][333][334][335][336][337][338][339] , and mouse alloantigen I-Ea [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] . Female 6-8-week-old C57BL/6 mice (The Jackson Laboratory, Bar Harbor, ME, USA) were inoculated by stereotactic injection of 6.0×10 4 -1.0×10 5 GL261 or GL261-Quad cells into the right striatum.…”

Standard of care therapy for malignant glioma and its effect on tumor and stromal cells

“…One adverse consequence of bevacizumab therapy is the induction of a more hypoxic tumor microenvironment potentially favoring a metabolic shift toward glycolysis in tumor cells and increasing tumor invasion into the normal brain parenchyma (Keunen et al, 2011). Some studies have looked at the effects of hypoxic conditions on stromal cells.…”

Glioblastoma: Current Chemotherapeutic Status and Need for New Targets and Approaches

“…Though favorable responses and anti-tumor effects occur with combination of various anti-angiogenic agents in different cancer models, efficacy of bevacizumab monotherapy in increasing glioblastoma patient survival has not transpired. Emergence of an invasive phenotype while angiogenesis is being targeted in glioblastoma constitutes a major limitation of anti-angiogenic monotherapies (Lamszus et al, 2003;Verhoeff et al, 2009;Keunen et al, 2011). Thus, improved therapies need to be developed to target glioblastoma.…”