TWEAK, short for TNF-related weak inducer of apoptosis, is also known as TNFSF12 and DR3LG. It is a type II transmembrane protein belonging to the TNF superfamily. It is expressed widely in many tissues, such as the heart, skeletal muscle, spleen and peripheral blood. Binding of TWEAK to its receptor TWEAKR induces NF-?B activation, chemokine secretion and apoptosis in certain cell types. TWEAK has also been reported to promote endothelial cell proliferation and migration, thus serving as a regulator of angiogenesis.