3028 - COPS8-Mediated Deneddylation of DHX9 Enhances Radioresistance in Non-Small Cell Lung Cancer via Facilitating DNA Damage Repair
Presenter(s)
S. Bao1,2, F. Wang1, C. Tian1, J. Ma1, H. Yang1, J. Liu1, J. Wang1, Y. Wang, M. Wu4, J. Yu4,5, and D. Chen1,6; 1Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China, 2Shandong University Cancer Center, Shandong University, Jinan, China, 3Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, 4Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China, 5Department of Radiation Oncology and Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
Purpose/Objective(s):
Neddylation is defined as ubiquitin-like modification that conducts the dynamic cycle of NEDD8 conjugation and deconjugation to the substrate. While aberrant neddylation/deneddylation homeostasis has been implicated in tumorigenesis, the functional significance of deneddylation enzymes in regulating radiotherapy response remains unexplored. This study investigates the mechanistic role of COP9 signalosome subunit 8 (COPS8), a critical deneddylase, in mediating radioresistance in non-small cell lung cancer (NSCLC).Materials/Methods:
The expression of COPS8 and NEDD8 in radiosensitive and radioresistance NSCLC tissues were validated by immunohistochemistry. The effect of COPS8 on radiosensitivity of NSCLC cells was explored through colony formation assay in vitro, and further verified by mouse xenograft tumor models in vivo. DNA double-strand breaks (DSBs) were detected using the neutral comet assay. Western blotting quantified DNA damage-related protein expression. COPS8 substrates were identified through co-immunoprecipitation/mass spectrometry (Co-IP/MS), with subsequent validation of DHX9 deneddylation by Co-IP and immunoblotting.Results:
Clinical analysis demonstrated that elevated COPS8 expression correlated with poor radiotherapy response and shorter progression-free survival (PFS) in NSCLC patients. Cellular experiments revealed that COPS8 overexpression reduced radiotherapy-induced DNA damage and enhanced radioresistance. Mechanistically, COPS8 directly interacted with DHX9, catalyzing its deneddylation at residues K697 and K806, thereby stabilizing DHX9 and enhancing its functionality. Rescue experiments confirmed the essential role of DHX9 in mediating COPS8-driven DNA damage suppression and radiation resistance. Furthermore, the COPS8-DHX9 axis inhibited RAD50 transcription, impairing DNA damage repair capacity.Conclusion:
Our findings establish that COPS8 upregulation drives NSCLC radioresistance through DHX9 deneddylation, resulting in compromised RAD50-dependent DNA repair. Pharmacological inhibition of DHX9 deneddylation synergized with radiotherapy in preclinical models, suggesting a potential therapeutic strategy for overcoming radioresistance in NSCLC.