Ang-2/VEGF bispecific antibody reprograms macrophages and resident microglia to anti-tumor phenotype and prolongs glioblastoma survival

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Abstract

Inhibition of the vascular endothelial growth factor (VEGF) pathway has failed to improve overall survival of patients with glioblastoma (GBM). We previously showed that angiopoietin-2 (Ang-2) overexpression compromised the benefit from anti-VEGF therapy in a preclinical GBM model. Here we investigated whether dual Ang-2/VEGF inhibition could overcome resistance to anti-VEGF treatment. We treated mice bearing orthotopic syngeneic (Gl261) GBMs or human (MGG8) GBM xenografts with antibodies inhibiting VEGF (B20), or Ang-2/VEGF (CrossMab, A2V). We examined the effects of treatment on the tumor vasculature, immune cell populations, tumor growth, and survival in both the Gl261 and MGG8 tumor models. We found that in the Gl261 model, which displays a highly abnormal tumor vasculature, A2V decreased vessel density, delayed tumor growth, and prolonged survival compared with B20. In the MGG8 model, which displays a low degree of vessel abnormality, A2V induced no significant changes in the tumor vasculature but still prolonged survival. In both the Gl261 and MGG8 models A2V reprogrammed protumor M2 macrophages toward the antitumor M1 phenotype. Our findings indicate that A2V may prolong survival in mice with GBM by reprogramming the tumor immune microenvironment and delaying tumor growth.

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Most cited references 35

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Selective ablation of immature blood vessels in established human tumors follows vascular endothelial growth factor withdrawal.

L. E. Benjamin, D Golijanin, A Itin … (1999)

Features that distinguish tumor vasculatures from normal blood vessels are sought to enable the destruction of preformed tumor vessels. We show that blood vessels in both a xenografted tumor and primary human tumors contain a sizable fraction of immature blood vessels that have not yet recruited periendothelial cells. These immature vessels are selectively obliterated as a consequence of vascular endothelial growth factor (VEGF) withdrawal. In a xenografted glioma, the selective vulnerability of immature vessels to VEGF loss was demonstrated by downregulating VEGF transgene expression using a tetracycline-regulated expression system. In human prostate cancer, the constitutive production of VEGF by the glandular epithelium was suppressed as a consequence of androgen-ablation therapy. VEGF loss led, in turn, to selective apoptosis of endothelial cells in vessels devoid of periendothelial cells. These results suggest that the unique dependence on VEGF of blood vessels lacking periendothelial cells can be exploited to reduce an existing tumor vasculature.

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FDA drug approval summary: bevacizumab (Avastin) as treatment of recurrent glioblastoma multiforme.

Martin H Cohen, Yuan Shen, Patricia Keegan … (2009)

On May 5, 2009, the U.S. Food and Drug Administration granted accelerated approval to bevacizumab injection (Avastin; Genentech, Inc., South San Francisco, CA) as a single agent for patients with glioblastoma multiforme (GBM) with progressive disease following prior therapy. The approval was based on durable objective responses (independent radiologic review with stable or decreasing corticosteroid use). Two trials evaluating bevacizumab, 10 mg/kg by i.v. infusion every 2 weeks, were submitted. One trial also randomized patients to bevacizumab plus irinotecan treatment. All patients had received prior surgery, radiotherapy, and temozolomide. Patients with active brain hemorrhage were excluded. One trial enrolled 78 independently confirmed GBM patients. Partial responses were observed in 25.9% (95% confidence interval [CI], 17.0%-36.1%) of the patients. The median response duration was 4.2 months (95% CI, 3.0-5.7 months). The second trial enrolled 56 GBM patients. Partial responses were observed in 19.6% (95% CI, 10.9%-31.3%) of the patients. The median response duration was 3.9 months (95% CI, 2.4-17.4 months). Safety data were provided for the first study. The most frequently reported bevacizumab adverse events of any grade were infection, fatigue, headache, hypertension, epistaxis, and diarrhea. Grade 3-5 bevacizumab-related adverse events included bleeding/hemorrhage, central nervous system (CNS) hemorrhage, hypertension, venous and arterial thromboembolic events, wound-healing complications, proteinuria, gastrointestinal perforation, and reversible posterior leukoencephalopathy. The attribution of certain adverse events (e.g., CNS hemorrhage, wound-healing complications, and thromboembolic events) to either bevacizumab, underlying disease, or both could not be determined because of the single-arm, noncomparative study design.

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The molecular profile of microglia under the influence of glioma.

Wei Li, Manuel Graeber (2012)

Microglia, which contribute substantially to the tumor mass of glioblastoma, have been shown to play an important role in glioma growth and invasion. While a large number of experimental studies on functional attributes of microglia in glioma provide evidence for their tumor-supporting roles, there also exist hints in support of their anti-tumor properties. Microglial activities during glioma progression seem multifaceted. They have been attributed to the receptors expressed on the microglia surface, to glioma-derived molecules that have an effect on microglia, and to the molecules released by microglia in response to their environment under glioma control, which can have autocrine effects. In this paper, the microglia and glioma literature is reviewed. We provide a synopsis of the molecular profile of microglia under the influence of glioma in order to help establish a rational basis for their potential therapeutic use. The ability of microglia precursors to cross the blood-brain barrier makes them an attractive target for the development of novel cell-based treatments of malignant glioma.