TWEAK (tumor necrosis factor-like weak inducer of apoptosis) is a member of the TNF superfamily that controls a multitude of cellular events including proliferation, migration, differentiation, apoptosis, angiogenesis, and inflammation. TWEAK exists in both membrane-bound and secreted forms, and can induce cell apoptosis via multiple pathways of cell death in a cell type-specific manner. It has also been found to promote the proliferation and migration of endothelial cells, and thus acts as a regulator of angiogenesis.