Cancer stem cells (CSCs) — known to be resistant to genotoxic radiation and chemotherapy — are fundamental to therapy failure and cancer relapse. Here, we reveal that glioma CSCs are hypersensitive to radiation, but a temporal DNA repair mechanism converts the intrinsic sensitivity to genomic instability and treatment resistance. Transcriptome analysis identifies DNA-dependent protein kinase (DNA-PK) as a predominant DNA repair enzyme in CSCs. Notably, DNA-PK activity is suppressed after irradiation when ROS induce the dissociation of DNA-PKcs with Ku70/80, resulting in delayed DNA repair and radiosensitivity; subsequently, after ROS clearance, the accumulated DNA damage and robust activation of DNA-PK induce genomic instability, facilitated by Rad50-mediated cell-cycle arrest, leading to enhanced malignancy, CSC overgrowth, and radioresistance. Finally, we show a requisite in vivo role for DNA-PK in CSC-mediated radioresistance and glioma progression. These findings identify a time-sensitive mechanism controlling CSC resistance to DNA-damaging treatments and suggest DNA-PK/Rad50 as promising targets for CSC eradication.
Yanling Wang, Haineng Xu, Tianrun Liu, Menggui Huang, Param-Puneet Butter, Chunsheng Li, Lin Zhang, Gary D. Kao, Yanqing Gong, Amit Maity, Constantinos Koumenis, Yi Fan
DNA-PK is selectively required for after radiation γ-H2AX and DNA repair in CSCs.