Tumor cells suppress radiation-induced immunity by hijacking caspase 9 signaling

Chuanhui Han, Zhida Liu, Yunjia Zhang, Aijun Shen, Chunbo Dong, Anli Zhang, Casey Moore, Zhenhua Ren, Changzheng Lu, Xuezhi Cao, Chun Li Zhang, Jian Qiao, Yang Xin Fu

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)546-554
Number of pages9
JournalNature immunology
Issue number5
StatePublished - May 1 2020

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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