EPHB4 and cancer: Cancer cells secrete various pro-angiogenic factors such as vascular endothelial growth factors (VEGFs) and its receptor (VEGF Receptor-2, VEGFR-2), angiopoietin (Ang) and its receptor (tyrosine kinase with Ig and epidermal growth factor homology domain-2, Tie-2), erythropoietin-producing hepatoma receptor B4 (EphB4) and its membrane-associated ligand, ephrinB2 [4–6].