TWEAK is a TNF family member produced by IFN-y-stimulated monocytes and induces multiple cell death pathways including caspase-dependent apoptosis and cathepsin B-dependent necrosis. These pathways are mediated by the binding of TWEAK by fibroblast growth factor 14 (Fn14), a member of the TNF receptor superfamily. Yeast two-hybrid experiments have shown that FN14 will bind to the TNFR-associated factors TRAF1, TRAF2, TRAF3, and TRAF5, suggesting that the signaling pathway induced by TWEAK may be mediated by one or more of these adaptor molecules. Fn14 is induced during liver regeneration and is highly expressed in hepatocellular carcinomas. In addition, TWEAK induces liver progenitor cell proliferation, suggesting Fn14 may play a role in hepatocyte growth control and liver neoplasia.