TRAIL/Apo2L,  also known as Tumor Necrosis Factor Super-Family 10 (TNFSF10), is a pleiotropic cytokine thatbelongs to the TNF superfamily. The full length TRAIL expressed in vivo is a Type II transmembrane protein, although the soluble form also exists and functions. TRAIL has four major receptors: two death receptors DR4 and DR5, two decoy receptors DcR1 and DcR2. TRAIL binds to the death receptors, recruits the FAS-associated death domain, activates caspases 8 and 10, and eventually leads to apoptosis. Because of its antitumor potential, TRAIL is actively studied as a therapeutic agent. On the other hand, abnormal expression of TRAIL in small arteries can induce the proliferation of smooth muscle cells, resulting in increasing vascular remodeling and pulmonary arterial hypertension. 
Recombinant human TRAIL/Apo2L (rhTRAIL)  produced in E. coli is a single non-glycosylated polypeptide chain containing 169 amino acids. A fully biologically active molecule, rhTRAIL has a molecular mass of 19.6 kDa analyzed by reducing SDS-PAGE and is obtained by proprietary chromatographic techniques at ExCell Bio.