Thrombospondin type-1 domain-containing protein 1, also known as transmembrane molecule with thrombospondin module, THSD1 and TMTSP, is a single-pass type I membrane protein which contains one TSP type-1 domain. THSD1 is a multi-domain, multi-functional glycoprotein synthesized by many cells. Matricellular THSD1 modulates cell adhesion and proliferation. It is involved in angiogenesis, inflammation, wound healing and cancer. In vitro, nanomolar concentrations of Thrombospondin-1 are required to alter endothelial and vascular smooth muscle cell adhesion, proliferation, motility, and survival. As a major platelet protein, for a long time it was postulated to control hemostasis via platelet aggregate stabilization. THSD1 is a potent angiogenesis inhibitor, and down-regulation of THSD1 has been suggested to alter tumor growth by modulating angiogenesis in a variety of tumor types.