ANGPT1 (angiopoietin 1) is a key vascular growth factor that binds and activates the TEK/TIE2 receptor, triggering its dimerization and tyrosine phosphorylation. In quiescent vessels with tight endothelial cell-cell contacts, ANGPT1 recruits TEK to cell-cell junctions, preferentially activating phosphatidylinositol 3-kinase and AKT signaling to promote vascular stability and inhibit angiogenesis. Conversely, in migrating endothelial cells lacking adhesions, ANGPT1 recruits TEK to focal adhesion complexes with the extracellular matrix, activating PTK2/FAK and downstream MAPK1/ERK2-MAPK3/ERK1 cascades to stimulate sprouting angiogenesis [PMID:UniProt]. ANGPT1 is essential for normal embryonic angiogenesis and heart development, and mediates blood vessel maturation and endothelial-mesenchymal interactions distinct from VEGF pathways. Clinically, ANGPT1 dysregulation contributes to multiple diseases. In venous malformations driven by PIK3CA mutations, excessive ANGPT1 from recruited smooth muscle cells exacerbates TIE2 signaling, with TIE2 inhibition suppressing disease progression 1. ANGPT1 expression increases during anti-angiogenesis therapy-induced vascular normalization in lung adenocarcinoma, mediated through pericyte recruitment and retinoic acid metabolism 2. ANGPT1 forms autocrine loops in RUNX1-MECOM leukemia cells, promoting survival through TEK phosphorylation and AKT activation 3. Genetic variants in ANGPT1 associate with ischemic stroke severity in mice and humans 4 and colorectal cancer survival outcomes 5. ANGPT1-modified mesenchymal stem cells demonstrate therapeutic potential in acute pancreatitis through angiogenesis promotion and inflammation reduction 6.