Abstract LB-346: Dual inhibition of Ang-2 and VEGF receptors normalizes tumor vasculature and prolongs survival in glioblastoma by altering macrophages

OBJECTIVE: Here we aimed to overcome resistance to anti-VEGF therapy in glioblastoma (GBM), the most common and aggressive adult primary brain tumor. INTRODUCTION: Current standard of care, including chemo-radiation, confers modest overall survival benefits of less than 1.5 years in patients. GBMs are highly dependent on angiogenesis, and anti-VEGF therapy is a promising approach to prolong survival. While anti-VEGF therapy prolongs progression-free survival in GBM, patients rapidly become refractory and overall survival is not increased. We previously demonstrated that angiopoietin-2 (Ang-2) may confer resistance to anti-VEGF receptor (VEGFR) treatment, as ectopic overexpression of Ang-2 compromises the benefits of VEGFR inhibition in murine GBM. Additionally, circulating Ang-2 levels in GBM patients rebound after an initial decrease following administration of cediranib, a pan-VEGFR tyrosine kinase inhibitor, suggesting Ang-2 may mediate resistance to anti-VEGF pathway inhibition. EXPERIMENTAL DESIGN: In two orthotopic models of GBM, Gl261 (murine) and U87 (human), we used MRI and Optical Frequency Domain Imaging (OFDI) to measure whether dual inhibition of Ang-2 and VEGFR reduces tumor burden and improves survival. We examined morphological changes in the tumor vasculature by immunohistochemistry, and phenotypical changes in tumor associated macrophages (TAMs) by flow cytometry. RESULTS: Dual therapy with cediranib (a pan-VEGFRs inhibitor) and MEDI3617 (an Ang-2 neutralizing antibody) improved survival over each therapy alone by delaying Gl261 growth. In U87 tumors, combined treatment increased tumor necrosis. Dual therapy enhanced morphological normalization of vessels and led to changes along the M1/M2 spectrum of CD45 + CD11b + F4/80 + TAMs. We analyzed the functional role of TAMs by inhibiting TAM recruitment with an anti-colony stimulating factor-1 antibody (anti-CSF-1) in combination with dual therapy. Depletion of TAMs compromised the survival benefit of anti-Ang-2/VEGFR therapy, suggesting that TAMs mediate the survival benefits of dual therapy. CONCLUSION: Here we successfully demonstrated that dual inhibition of Ang-2 and VEGFRs prolongs survival in preclinical GBM models by reducing the viable tumor burden, improving vascular normalization, and reshaping the tumor immune-microenvironment mediated by TAMs. This combination may represent a potential therapeutic strategy to overcome the limitations of anti-VEGF monotherapy in GBM patients by integrating the complementary effects of anti-Ang2 treatment on vessels and immune cells. Citation Format: Zohreh Amoozgar, Teresa E. Peterson, Nathaniel D. Kirkpatrick, Yuhui Huang, Christian T. Farrar, Koen A. Marijt, Jonas Kloepper, Meenal Datta, Giorgio Seano, Keehoon Jung, Walid S. Kamoun, Trupti Vardam, Matija Snuderl, Jermaine Goveia, Sampurna Chatterjee, Ana Batista, Alona Muzikansky, Ching Ching Leow, Lei Xu, Tracy T. Batchelor, Dan G. Duda, Dai Fukumura, Jain K. Jain. Dual inhibition of Ang-2 and VEGF receptors normalizes tumor vasculature and prolongs survival in glioblastoma by altering macrophages. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-346.