KDR and glioma: In addition to this, molecules typically expressed on endothelial tip cells such as VEGFR-2, Neuropilin-1, Angiopoietin-2 (Ang-2), Integrin-ß1 and others have been described to be present in glioma vessels in situ [11, 31, 114], implying that tip and stalk cell phenotypes co-exist in the glioblastoma vasculature.