PROTAC-mediated structure–function disruption of CD26: a therapeutic strategy for driver-negative non-small cell lung cancerResearch in context

Summary: Background: Previous targeted therapies for non-small cell lung cancer (NSCLC) have focused on targeting driver mutations (e.g., EGFR/ALK), leading to approximately 30–40% of patients with negative mutations lacking effective treatments. Therefore, there is an urgent need for innovative therapeutic strategies for these patients. Methods: CD26-targeted proteolysis-targeting chimeras (PROTACs: P4-1 to P4-4) were designed and synthesised. The binding strengths between degraders and CD26 were evaluated through surface plasmon resonance (SPR). The ternary complex formations were confirmed by NanoBRET™ live-cell ternary complex profiling assay. Driver-negative NSCLC (NCI-H460 and NCI-H1299) and BEAS-2B cells were used to study the degradation performances of degraders. The therapeutic efficacies of the optimal degrader (P4-3) were assessed via cell line-derived xenografts (CDX), in situ lung cancer and patient-derived organoids (PDOs) models. Mechanistic studies incorporated co-immunoprecipitation, immunofluorescence, reactive oxygen species (ROS)/DNA damage detection, apoptosis assays and transcriptomics. Findings: CD26 underwent clathrin-dependent endocytosis induced by P4-3 and ternary complex were formed before protein degradation. Degradation of CD26 by P4-3 resulted in the cytoplasmic translocation of membrane-bound adenosine deaminase (ADA), leading to adenosine depletion, mitochondrial ROS accumulation, metabolic stress, DNA damage, and intrinsic apoptosis in vitro, in vivo and in PDOs (negative mutations) models. Mechanistically, degradation of CD26 uniquely eliminates both its enzymatic activity and non-enzymatic functions, achieving a dual effect unattainable with conventional inhibitors. Interpretation: Targeted CD26 degradation represents a valuable therapeutic strategy for driver-negative NSCLC. And this approach also addresses the limitations of driver mutation-targeted based therapies, providing a promising method for NSCLC patients with negative mutations. Funding: This study was funded by the Key Research and Development Project of Shaanxi Province (2023-YBSF-292), the opening foundation (M2022-3) from Key Laboratory of Optic-Electric Sensing and Analytical Chemistry for Life Science, Ministry of Education, Qingdao University of Science and Technology, the National Natural Science Foundation of China (82102976, 52203337), the Youth Top Talent Program (11301223010722) from Xi’an Jiaotong University, the Key Research and Development Project of Shaanxi Province (2024SF-ZDCYL-02-09) and Capacity Improvement Plan of Shaanxi Health Committee (2024PT-09).