Apoptosis is induced by certain cytokines including TNF and Fas ligand in the TNF family through their death domain containing receptors. TRAIL/Apo2L is a new member of the TNF family. DR4 was recently identified as the receptor for TRAIL. A novel death domain containing receptor for TRAIL was more recently identified and designated DR5, Apo2, TRAIL-R2, TRICK2, or KILLER by several groups independently. Like DR4, DR5 transcript is widely expressed in normal tissues and in many types of tumor cells. DR5 binds to TRAIL and mediates TRAIL induced cell death. Overexpression of DR5 induces apoptosis and activates NF-κB.