TEK and pancreatic insulinoma: Angiopoietin-1 (Ang-1), a Tie2 ligand, is likely to promote the recruitment of TEMs to tumor vasculature before the turn-on of the angiogenic switch in early stages of N202 breast carcinoma, Rip1-Tag2 pancreatic insulinoma and U87 human glioma (63, 65, 66).