Angiopoietin-1 (Ang-1) is a multimeric ligand involved in the angiopoietin-Tie signaling system that activates Tie2. It is predominantly expressed by endothelial cells and some smooth muscle cells, with increased expression in many inflammatory and angiogenic conditions, such as inflammation-induced vascular remodeling and tumor angiogenesis. Ang-1 expression has been documented in a range of human cancers, including glioblastoma, melanoma, prostate adenocarcinoma, and renal cell carcinoma.