Targeting A20 enhances TRAIL-induced apoptosis in hepatocellular carcinoma cells

A20 was initially identified as a primary gene product following TNF α treatment in human umbilical vein endothelial cells. Increased A20 expression is associated with tumorigenesis in many cancers, whereas the loss of A20 function is linked to lymphoma. It has been reported that A20 protects cells from TRAIL-induced apoptosis; however, the mechanism by which A20 is involved is still largely unknown. Our results indicate that TRAIL induces the hepatocellular carcinoma apoptosis associated with A20 knockdown in a concentration-dependent manner. TRAIL-induced apoptosis requires p18 caspase-8 activation, and, the activation of caspase-8 is at least in part, due to the direct cleavage of RIP1 by A20 knockdown. These findings suggest that A20 modulates the sensitivity to TRAIL by RIP1 ubiquitination, thereby repressing the recruitment and activation of pro-caspase-8 into the active form caspase-8. Thus, our study suggests that A20 protects against TRAIL-induced apoptosis through the regulation of RIP1 ubiquitination.

► A20 is highly expressed in human hepatocellular carcinoma tissues.
► Caspase-8 cleavage is inhibited in TRAIL resistance.
► Targeting A20 enhances TRAIL-induced apoptosis.
► A20 mediates RIP1 ubiquitination to inhibit caspase-8 cleavage.