Thrombs-1 (THBS-1) is a member of the thrombs-retin family that mediates cell-cell and cell-matrix interactions. The protein can bind to fibrinogen, fipronectin, laminin, type V collagen and integrin α-V/β-1. It plays a role in platelet aggregation, angiogenesis and tumorigenesis. In normal tissues, it is a natural inhibitor of new blood vessel formation and tumorigenesis. THBS-1 also positively and negatively regulates endothelial cell adhesion, movement and growth. By blocking the binding of THBS-1 to the cell surface receptor (CD47), normal tissues become almost immune to tumor radiation therapy and contribute to tumor death.