Dll4 is expressed in tumor vasculature [26,36,53,54], and as observed in studies of developmental angiogenesis, the blockade of Dll4-mediated Notch signaling (via systemic administration of Dll4-neutralizing antibodies [47,48] and systemic or local administration of modified Dll4 proteins [47,55]) increased tumor-vessel sprouting, which indicates that Dll4-Notch signaling is critical for tip- and stalk-cell selection during tumor angiogenesis. Here, DLL4 is linked to neoplasm.