DR4 is 56 kD member 10A of the TNFR superfamily (TNFRSF10A), also known as TRAIL-R1, Apo-2, and CD261. It is expressed at low levels by activated T cells and some tumors. After TRAIL engagement, DR4 (TRAIL-R1), through activation of NF-κB, induces apoptosis in the TRAIL ligated cell.