Tumor necrosis factor ligand superfamily member 12 also known as TNF-related weak inducer of apoptosis (TWEAK) is a protein that in humans is encoded by the TNFSF12 gene. The protein encoded by this gene is a cytokine that belongs to the tumor necrosis factor (TNF) ligand family. This protein is a ligand for the FN14/TWEAKR receptor. This cytokine has overlapping signaling functions with TNF, but displays a much wider tissue distribution. This cytokine, which exists in both membrane-bound and secreted forms, can induce apoptosis via multiple pathways of cell death in a cell type-specific manner. This cytokine is also found to promote proliferation and migration of endothelial cells, and thus acts as a regulator of angiogenesis. Alternative splicing results in multiple transcript variants.