Inactivation of DNA-PK by knockdown DNA-PKcs or NU7441 impairs non-homologous end-joining of radiation-induced double strand break repair

Dong,Jun; Ren,Yufeng; Zhang,Tian; Wang,Zhenyu; Ling,Clifton   C.; Li,Gloria   C.; He,Fuqiu; Wang,Chengtao; Wen,Bixiu

doi:10.3892/or.2018.6217

Inactivation of DNA-PK by knockdown DNA-PKcs or NU7441 impairs non-homologous end-joining of radiation-induced double strand break repair

Authors:
- Jun Dong
- Yufeng Ren
- Tian Zhang
- Zhenyu Wang
- Clifton C. Ling
- Gloria C. Li
- Fuqiu He
- Chengtao Wang
- Bixiu Wen
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Affiliations: Department of Radiation Oncology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510080, P.R. China, Department of Medical Physics and Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
Published online on: January 16, 2018 https://doi.org/10.3892/or.2018.6217
Pages: 912-920
Copyright: © Dong et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

The DNA-dependent protein kinase (DNA-PK) complex plays a pivotal role in non-homologous end-joining (NHEJ) repair. We investigated the mechanism of NU7441, a highly selective DNA-PK inhibitor, in NHEJ-competent mouse embryonic fibroblast (MEF) cells and NHEJ-deficient cells and explored the feasibility of its application in radiosensitizing nasopharyngeal carcinoma (NPC) cells. We generated wild-type and DNA-PKcs-/- MEF cells. Clonogenic survival assays, flow cytometry, and immunoblotting were performed to study the effect of NU7441 on survival, cell cycle, and DNA repair. NU7441 profoundly radiosensitized wild-type MEF cells and SUNE-1 cells, but not DNA-PKcs-/- MEF cells. NU7441 significantly suppressed radiation-induced DSB repair post-irradiation through unrepaired and lethal DNA damage, the cell cycle arrest. The effect was associated with the activation of cell cycle checkpoints. The present study revealed a mechanism by which inhibition of DNA-PK sensitizes cells to irradiation suggesting that radiotherapy in combination with DNA-PK inhibitor is a promising paradigm for the management of NPC which merits further investigation.

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