||Tumor necrosis factor ligand superfamily member 12 (TNFSF12) also known as TNF-related weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor ligand (TNF) ligand family. Nineteen cytokines have been identified as part of the TNF family on the basis of sequence, functional, and structural similarities. Family members include TNF beta (TNFSF1), TNF alpha (TNFSF2), Lymphotoxin beta (TNFSF3), OX40 Ligand (TNFSF4), CD40 Ligand (TNFSF5), Fas Ligand (TNFSF6), CD27 Ligand (TNFSF7), CD30 Ligand (TNFSF8), 4-1BB Ligand (TNFSF9), TRAIL (TNFSF10), TRANCE/RANKL (TNFSF11), TWEAK (TNFSF12), APRIL(TNFSF13), BAFF (TNFSF13B), LIGHT (TNFSF14), TL1A/VEGI (TNFSF15), and GITR Ligand (TNFSF18). TWEAK has overlapping signaling functions with TNF, but displays a much wider tissue distribution. TWEAK can induce apoptosis via multiple pathways of cell death in a cell type-specific manner. TWEAK is also found to promote proliferation and migration of endothelial cells, and thus acts as a regulator of angiogenesis.