KDR and cancer: Whereas VEGFR-2 can be readily detected in glioma cell lines in vitro, most studies suggest that in both murine and human glioma specimens in vivo expression of VEGFR-2 is mainly confined to vascular endothelial cells [51, 52, 77, 87, 112–114, 136], and potentially to a subset of cancer stem-like cells [49].