ANGPT1 and neoplasm: Holash and coworkers observed the process of vessel co-option to be followed by vessel regression, tumor hypoxia, and the stimulation of angiogenesis for further growth to be based on the relative expression of pro- and antiangiogenic endothelial growth factors (angiopoietin-1 and -2 and vascular endothelial growth factor, VEGF) 14.