CXCR4 and glioma: In glioma-derived EVs from the cell line U251, several pro-angiogenic factors were identified, including the vascular endothelial growth factor (VEGF), the C-X-C chemokine receptor type 4 (CXCR4), the transforming growth factor b type 1 (TGF-b1), and matrix metalloproteinases (MMPs) [41].