Feed

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) selectively induces apoptosis in cancer cells. However, many cancer cells are resistant to TRAIL because of downregulation of death receptors (DRs) and overexpression of anti-apoptotic proteins. Ubiquitin-conjugating enzyme E2N (UBE2N), also known as Ubc13, plays a central role in ubiquitin-mediated cellular activities. In this study, we aimed to explore the sensitization effect of UBE2N inhibition in TRAIL-mediated apoptosis in cancer cells. NSC697923 (a potent inhibitor of UBE2N) alone and TRAIL alone did not induce apoptosis in renal carcinoma Caki cells. However, combined treatment with NSC697923 and TRAIL significantly enhanced apoptotic cell death in cancer cells, but not in normal cells. Mechanistically, NSC697923 induced upregulation of DR5 mRNA and protein levels through CHOP-mediated DR5 transcriptional activation and ubiquitin-mediated DR5 stabilization. NSC697923-mediated DR5 mRNA upregulation was regulated by upregulation of CHOP expression, a key transcriptional factor of DR5. CHOP siRNA treatment inhibited NSC697923-mediated DR5 protein expression. Moreover, NSC697923 generated ROS, and pretreatment with ROS scavengers inhibited DR5 upregulation and NSC697923 plus TRAIL-mediated cell death. These findings suggest that UBE2N inhibitor enhances TRAIL-induced apoptosis by DR5 upregulation and UBE2N inhibition may serve as a potential strategy to overcome TRAIL resistance in cancer therapy.