1. Tumor cells suppress radiation-induced immunity by hijacking caspase 9 signaling
- Author
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Aijun Shen, Zhenhua Ren, Jian Qiao, Zhida Liu, Chun Li Zhang, Casey Moore, Yang Xin Fu, Yunjia Zhang, Chunbo Dong, Anli Zhang, Chuanhui Han, Changzheng Lu, and Xuezhi Cao
- Subjects
0301 basic medicine ,Mitochondrial DNA ,Immunology ,B7-H1 Antigen ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,Antineoplastic Agents, Immunological ,0302 clinical medicine ,Downregulation and upregulation ,Cell Line, Tumor ,Animals ,Humans ,Immunology and Allergy ,Pentanoic Acids ,Caspase ,Mice, Knockout ,Caspase-9 ,Mice, Inbred BALB C ,biology ,Chemistry ,Chemoradiotherapy ,Caspase Inhibitors ,Caspase 9 ,Up-Regulation ,Cell biology ,Mice, Inbred C57BL ,Disease Models, Animal ,030104 developmental biology ,Drug Resistance, Neoplasm ,Cell culture ,Apoptosis ,biology.protein ,Female ,Signal transduction ,Colorectal Neoplasms ,Neoplasm Transplantation ,DNA ,Signal Transduction ,030215 immunology - Abstract
High-dose radiation activates caspases in tumor cells to produce abundant DNA fragments for DNA sensing in antigen-presenting cells, but the intrinsic DNA sensing in tumor cells after radiation is rather limited. Here we demonstrate that irradiated tumor cells hijack caspase 9 signaling to suppress intrinsic DNA sensing. Instead of apoptotic genomic DNA, tumor-derived mitochondrial DNA triggers intrinsic DNA sensing. Specifically, loss of mitochondrial DNA sensing in Casp9-/- tumors abolishes the enhanced therapeutic effect of radiation. We demonstrated that combining emricasan, a pan-caspase inhibitor, with radiation generates synergistic therapeutic effects. Moreover, loss of CASP9 signaling in tumor cells led to adaptive resistance by upregulating programmed death-ligand 1 (PD-L1) and resulted in tumor relapse. Additional anti-PD-L1 blockade can further overcome this acquired immune resistance. Therefore, combining radiation with a caspase inhibitor and anti-PD-L1 can effectively control tumors by sequentially blocking both intrinsic and extrinsic inhibitory signaling.
- Published
- 2020
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