Angiopoietin-2 Interferes with Anti-VEGFR2–Induced Vessel Normalization and Survival Benefit in Mice Bearing Gliomas

Purpose: In brain tumors, cerebral edema is a significant source of morbidity and mortality. Recent studies have shown that inhibition of vascular endothelial growth factor (VEGF) signaling induces transient vascular normalization and reduces cerebral edema, resulting in a modest survival benefit in glioblastoma patients. During anti-VEGF treatment, circulating levels of angiopoietin (Ang)-2 remained high after an initial minor reduction. It is not known, however, whether Ang-2 can modulate anti-VEGF treatment of glioblastoma. Here, we used an orthotopic glioma model to test the hypothesis that Ang-2 is an additional target for improving the efficacy of current anti-VEGF therapies in glioma patients. Experimental Design: To recapitulate high levels of Ang-2 in glioblastoma patients during anti-VEGF treatment, Ang-2 was ectopically expressed in U87 glioma cells. Animal survival and tumor growth were assessed to determine the effects of Ang-2 and anti–VEGF receptor 2 (VEGFR2) treatment. We also monitored morphologic and functional vascular changes using multiphoton laser scanning microscopy and immunohistochemistry. Results: Ectopic expression of Ang-2 had no effect on vascular permeability, tumor growth, or survival, although it resulted in higher vascular density, with dilated vessels and reduced mural cell coverage. On the other hand, when combined with anti-VEGFR2 treatment, Ang-2 destabilized vessels without affecting vessel regression and compromised the survival benefit of VEGFR2 inhibition by increasing vascular permeability. VEGFR2 inhibition normalized tumor vasculature whereas ectopic expression of Ang-2 diminished the beneficial effects of VEGFR2 blockade by inhibiting vessel normalization. Conclusion: Cancer treatment regimens combining anti-VEGF and anti-Ang-2 agents may be an effective strategy to improve the efficacy of current anti-VEGF therapies. Clin Cancer Res; 16(14); 3618–27. ©2010 AACR.

[1]  Dai Fukumura,et al.  Simultaneous measurement of RBC velocity, flux, hematocrit and shear rate in tumor vascular networks , 2010, Nature Methods.

[2]  Thomas Benner,et al.  Phase II study of cediranib, an oral pan-vascular endothelial growth factor receptor tyrosine kinase inhibitor, in patients with recurrent glioblastoma. , 2010, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[3]  R. Jain,et al.  Simultaneous measurement of RBC velocity, flux, hematocrit and shear rate in vascular networks in vivo , 2010 .

[4]  D. McDonald,et al.  Complementary actions of inhibitors of angiopoietin-2 and VEGF on tumor angiogenesis and growth. , 2010, Cancer research.

[5]  P. Koumoutsakos,et al.  Tumorigenesis and Neoplastic Progression Contrasting Actions of Selective Inhibitors of Angiopoietin-1 and Angiopoietin-2 on the Normalization of Tumor Blood Vessels , 2009 .

[6]  A. Harris,et al.  Contribution of granulocyte colony-stimulating factor to the acute mobilization of endothelial precursor cells by vascular disrupting agents. , 2009, Cancer research.

[7]  M. Bernaudin,et al.  MRI assessment of hemodynamic effects of angiopoietin-2 overexpression in a brain tumor model. , 2009, Neuro-oncology.

[8]  Dushyant V. Sahani,et al.  Biomarkers of response and resistance to antiangiogenic therapy , 2009, Nature Reviews Clinical Oncology.

[9]  R. Jain,et al.  Edema control by cediranib, a vascular endothelial growth factor receptor-targeted kinase inhibitor, prolongs survival despite persistent brain tumor growth in mice. , 2009, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[10]  Y. Meng,et al.  G-CSF-initiated myeloid cell mobilization and angiogenesis mediate tumor refractoriness to anti-VEGF therapy in mouse models , 2009, Proceedings of the National Academy of Sciences.

[11]  Gavin Thurston,et al.  Control of vascular morphogenesis and homeostasis through the angiopoietin–Tie system , 2009, Nature Reviews Molecular Cell Biology.

[12]  D. Schadendorf,et al.  Host-derived angiopoietin-2 affects early stages of tumor development and vessel maturation but is dispensable for later stages of tumor growth. , 2009, Cancer research.

[13]  P. Kelly,et al.  Antiangiogenic therapy using bevacizumab in recurrent high-grade glioma: impact on local control and patient survival. , 2009, Journal of neurosurgery.

[14]  L. Vallières,et al.  Reduced Glioma Growth Following Dexamethasone or Anti‐Angiopoietin 2 Treatment , 2008, Brain pathology.

[15]  R. Jain,et al.  Characterization of blood vessels in brain autopsies of GBM patients who received antiangiogenic treatment , 2008 .

[16]  I. Cree,et al.  Angiopoietin modulation of vascular endothelial growth factor: Effects on retinal endothelial cell permeability. , 2007, Cytokine.

[17]  T. Mccauley,et al.  Sequential loss of tumor vessel pericytes and endothelial cells after inhibition of platelet-derived growth factor B by selective aptamer AX102. , 2007, Cancer research.

[18]  M. Dewhirst,et al.  Systemic overexpression of angiopoietin-2 promotes tumor microvessel regression and inhibits angiogenesis and tumor growth. , 2007, Cancer research.

[19]  M. Atkins,et al.  Angiopoietin 2 Is a Potential Mediator of High-Dose Interleukin 2–Induced Vascular Leak , 2007, Clinical Cancer Research.

[20]  K. Aldape,et al.  Sustained angiopoietin-2 expression disrupts vessel formation and inhibits glioma growth. , 2006, Neoplasia.

[21]  Ricky T. Tong,et al.  Surrogate markers for antiangiogenic therapy and dose-limiting toxicities for bevacizumab with radiation and chemotherapy: continued experience of a phase I trial in rectal cancer patients. , 2005, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[22]  E. Lo,et al.  Granulocyte colony-stimulating factor enhances angiogenesis after focal cerebral ischemia , 2005, Brain Research.

[23]  Peter Vajkoczy,et al.  Combined inhibition of VEGF‐ and PDGF‐signaling enforces tumor vessel regression by interfering with pericyte‐mediated endothelial cell survival mechanisms , 2004, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[24]  D. Hanahan,et al.  Benefits of targeting both pericytes and endothelial cells in the tumor vasculature with kinase inhibitors. , 2003, The Journal of clinical investigation.

[25]  W. Schaper,et al.  In vitro effects of dexamethasone on hypoxia-induced hyperpermeability and expression of vascular endothelial growth factor. , 2001, European journal of pharmacology.

[26]  M. Dewhirst,et al.  Antiangiogenic gene therapy targeting the endothelium-specific receptor tyrosine kinase Tie2. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[27]  Brygida Berse,et al.  Vascular permeability factor (VPF, VEGF) in tumor biology , 1993, Cancer and Metastasis Reviews.

[28]  W. D. den Dunnen,et al.  The angiopoietin 1/angiopoietin 2 balance as a prognostic marker in primary glioblastoma multiforme. , 2009, Journal of neurosurgery.

[29]  Tracy T Batchelor,et al.  AZD2171, a pan-VEGF receptor tyrosine kinase inhibitor, normalizes tumor vasculature and alleviates edema in glioblastoma patients. , 2007, Cancer cell.