TWEAK is a 27 kD protein also known as tumor necrosis factor superfamily member 12 (TNFSF12), TNF-related weak inducer of apoptosis, and CD255. TWEAK is a type II transmembrane protein expressed on a variety of cell types. A soluble form of TWEAK is produced by proteolytic processing. TWEAK binds to the TWEAK receptor, FN14, to induce apoptosis, NF-kappaB translocation, and promote angiogenesis and endothelial cell proliferation. It has also been implicated in the induction of inflammatory cytokines.