TWEAK (TNFSF12/Apo-3L) is a member of the TNF superfamily of cytokines that are typically involved in immune regulation, inflammation, and apoptosis (1,2). TWEAK mRNA is expressed in a variety of tissues and cell lines, with higher levels observed in the heart, brain, skeletal muscle and within the immune system (1). Like other family members TWEAK is a type II transmembrane protein that can also be proteolytically processed to form a soluble cytokine. Soluble TWEAK is a weak inducer of apoptosis in some cell lines (1). The receptor for TWEAK, known as TWEAKR or fibroblast growth factor inducible 14 (Fn14), is a relatively small member of the TNF receptor family (3). TWEAK signaling has been associated with apoptosis, proliferation, migration, angiogenesis, and inflammation (4). Recent studies have suggested some therapeutic potential of TWEAK and its receptor signaling in regards to autoimmunity, cancer, and vascular injury (5-8).