KDR and osteosarcoma: In addition to its constitutive expression on endothelial cells, presence of VEGFR2 on cancer cells was also confirmed in breast cancer [6, 7] [8, 9], lung cancer [10], glioblastoma [11], gastrointestinal cancer [12], hepatocellular carcinoma, renal cell carcinoma [13], ovarian cancer [14], bladder cancer [15], and osteosarcoma [16].