ANGPT1 and neoplasm: Hypoxic cells of the tumor mass, via the secretion of proangiogenic factors such as vascular endothelial growth factor (VEGF), Angiopoietin-1 and 2 (Ang1/2), or platelet-derived growth factor (PDGF), initiate angiogenic switch by stimulating peripheral endothelial cells of parenchymal tissue microvasculature.