Direct contact with perivascular tumor cells enhances integrin αvβ3 signaling and migration of endothelial cells

// Monica E. Burgett 1, 6 , Justin D. Lathia 2 , Patrick Roth 7 , Amy S. Nowacki 4 , Deni S. Galileo 10 , Elena Pugacheva 8 , Ping Huang 1 , Amit Vasanji 9 , Meizhang Li 2 , Tatiana Byzova 5 , Tom Mikkelsen 11 , Shideng Bao 3 , Jeremy N. Rich 3 , Michael Weller 7 , Candece L. Gladson 1 1 Department of Cancer Biology, Cleveland Clinic, Cleveland, OH, USA 2 Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, OH, USA 3 Department of Stem Cell Biology and Regenerative Medicine, Cleveland Clinic, Cleveland, OH, USA 4 Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, OH, USA 5 Department of Molecular Cardiology, Cleveland Clinic, Cleveland, OH, USA 6 School of Biomedical Sciences, Kent State University, Kent, OH, USA 7 Department of Neurology, Laboratory of Molecular Neuro-Oncology, University Hospital, Zurich, Switzerland 8 Department of Biochemistry, West Virginia University, Morgantown, VA, USA 9 Image IQ, Inc., Cleveland, OH, USA 10 Department of Biological Sciences, University of Delaware and Helen F. Graham Cancer Center and Research Institute, Christiana Care Health System, Newark, DE, USA 11 Department of Neurosurgery, Henry Ford Hospital, Detroit, MI, USA Correspondence to: Candece L. Gladson, email: gladsoc@ccf.org Keywords: endothelial cells, glioblastoma, angiogenesis, integrin αvβ3, cancer stem cells Received: September 24, 2015      Accepted: May 13, 2016      Published: May 30, 2016 ABSTRACT The secretion of soluble pro-angiogenic factors by tumor cells and stromal cells in the perivascular niche promotes the aggressive angiogenesis that is typical of glioblastoma (GBM). Here, we show that angiogenesis also can be promoted by a direct interaction between brain tumor cells, including tumor cells with cancer stem-like properties (CSCs), and endothelial cells (ECs). As shown in vitro , this direct interaction is mediated by binding of integrin αvβ3 expressed on ECs to the RGD-peptide in L1CAM expressed on CSCs. It promotes both EC network formation and enhances directed migration toward basic fibroblast growth factor. Activation of αvβ3 and bone marrow tyrosine kinase on chromosome X (BMX) is required for migration stimulated by direct binding but not for migration stimulated by soluble factors. RGD-peptide treatment of mice with established intracerebral GBM xenografts significantly reduced the percentage of Sox2-positive tumor cells and CSCs in close proximity to ECs, decreased integrin αvβ3 and BMX activation and p130CAS phosphorylation in the ECs, and reduced the vessel surface area. These results reveal a previously unrecognized aspect of the regulation of angiogenesis in GBM that can impact therapeutic anti-angiogenic targeting.