KDR and glioma: To verify GBM microenvironment-dependent alternation of VEGFR expression, human microvascular ECs, isolated from fetal and adult brain tissues (almost all of these cells were vWF+NG-2−, Supplementary Fig. 1), were treated with glioma-conditioned medium (glioma-CM, collected from human U251 or primary GBM cells cultured under hypoxia) in vitro.