Abstract 3898: Glioma stem cells promote brain endothelial cell motility: a new mechanism for the direct interaction of glioma stem cells with endothelial cells.

Abstract

Abstract Angiogenesis, the development of a neovasculature, is a key histologic feature of malignant glioma. It occurs through multiple mechanisms, including sprouting and migration of existing endothelial cells (ECs), and is driven by signals in the microenvironment. Glioma stem cells (GSC) inhabit a region near ECs (perivascular niche). Here we examined the hypothesis that GSCs interact directly with ECs and promote EC motility. In 4 of 5 glioblastoma biopsies we found that ∼40% of GSCs were localized within 25 μm of ECs, based on double-labeling for Sox2 and vWf. We then examined the effect of GSCs on EC motility when plated on a 2D laminin substrate, and found a significant increase in EC motility in the presence of GSCs as well as a direct interaction. In a 3D assay, EC migration was enhanced by GSC-conditioned media, but the physical presence and interaction between ECs and GSCs further increased EC migration through a laminin-coated, 3-μm pore filter, as compared to GSC-conditioned media. Integrin αvβ3 and L1CAM have been reported to be upregulated on ECs and GSCs, respectively, in GBM tumors, and integrin αvβ3 can bind the RGD-peptide in L1CAM. We examined the effect of blocking or downregulating integrin αvβ3 or L1CAM on EC interaction with GSCs. In a cell-cell binding assay, blocking or downregulating the integrin β3 subunit significantly inhibited EC-GSC direct contact, as did an RGD peptide and an antibody to L1CAM. Furthermore, downregulation of integrin β3 on ECs significantly reduced EC migration in the presence of GSCs in the transwell migration assay and reduced EC association with GSCs in mouse brain slices in organotypic culture, analyzed by 2-Photon-LSM. These data suggest GSCs promote angiogenesis in part by promoting EC motility, and that the EC-GSC direct interaction mediated by integrin αvβ3 on ECs and L1CAM on GSCs also stimulates EC motility. Citation Format: Monica E. Burgett, Ping Huang, Russell S. Tipps, Amit Vasanji, Justin D. Lathia, Meizhang Li, Shideng Bao, Jeremy N. Rich, Candece L. Gladson. Glioma stem cells promote brain endothelial cell motility: a new mechanism for the direct interaction of glioma stem cells with endothelial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3898. doi:10.1158/1538-7445.AM2013-3898