DLL4 and neoplasm: Vascular development in tumours occurs via the release of various endothelial growth factors and angiogenesis regulators (i.e. vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF), delta-like ligand 4 (Dll4)), leading to neo-vascularization predominantly via a sprouting process reminiscent of embryonic development [1]–[3].