The NEDD8-activating enzyme inhibitor, MLN4924, cooperates with TRAIL to augment apoptosis through facilitating c-FLIP degradation in head and neck cancer cells

• Type of Material: Article
• Authors: Liqun Zhao, Emory University; Ping Yue, Emory University; Sagar Lonial, Emory University; Fadlo Khuri, Emory University; Shi-Yong Sun, Emory University
• Language: English
• Date: 2011-12
• Publisher: American Association for Cancer Research
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: ©2011 American Association for Cancer Research
• Final Published Version (URL): http://dx.doi.org/10.1158%2F1535-7163.MCT-11-0401
• Title of Journal or Parent Work: Molecular Cancer Therapeutics
• ISSN: 1535-7163
• Volume: 10
• Issue: 12
• Start Page: 2415
• End Page: 2425
• Grant/Funding Information: Georgia Cancer Coalition Distinguished Cancer Scholar award (to S-Y. S.) and National Cancer Institute NIH SPORE P50 grant CA128613 (project 2 to S-Y. S and F. R. K).
• Keywords: TRAIL; head and neck cancer; c-FLIP; apoptosis; JNK; MLN4924
• Research Categories: Health Sciences, Oncology

Abstract

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a tumor-selective cytokine with potential anticancer activity and is currently under clinical testing. Head and neck squamous cell carcinoma (HNSCC), like other cancer types, exhibits varied sensitivity to TRAIL. MLN4924 is a newly developed investigational small molecule inhibitor of NEDD8-activating enzyme with potent anticancer activity. This study reveals a novel function of MLN4924 in synergizing with TRAIL to induce apoptosis in HNSCC cells. MLN4924 alone effectively inhibited the growth of HNSCC cells and induced apoptosis. When combined with TRAIL, synergistic effects on decreasing the survival and inducing apoptosis of HNSCC cells occurred. MLN4924 decreased c-FLIP levels without modulating DR4 and DR5 expression. Enforced expression of c-FLIP substantially attenuated MLN4924/TRAIL-induced apoptosis. Thus c-FLIP reduction plays an important role in mediating MLN4924/TRAIL-induced apoptosis. Moreover MLN4924 decreased c-FLIP stability, increased c-FLIP ubiquitination and facilitated c-FLIP degradation, suggesting that MLN4924 decreases c-FLIP levels through promoting its degradation. MLN4924 activated JNK signaling, evidenced by increased levels of phospho-c-Jun in MLN4924-treated cells. Chemical inhibition of JNK activation not only prevented MLN4924-induced c-FLIP reduction, but also inhibited MLN4924/TRAIL-induced apoptosis, suggesting that JNK activation mediates c-FLIP downregulation and subsequent enhancement of TRAIL-induced apoptosis by MLN4924. Since knockdown of NEDD8 failed to activate JNK signaling and downregulate c-FLIP, it is likely that MLN4924 reduces c-FLIP levels and enhances TRAIL-induced apoptosis independent of NEDD8 inhibition.