Objective      To investigate the impact of polynucleotide kinase/phosphatase (PNKP) silencing on radiation-induced DNA damage

apoptosis

cell proliferation and cell cycle in osteosarcoma cells.       Methods      U2OS cells were divided into control (Ctrl) group

negative siRNA (siC) group and siPNKP group. After different doses (0

1

2

4

6 and 8 Gy) of γ-ray irradiation

the changes of PNKP level and cell survival rate were determined using Western blotting and CCK-8 assay. After irradiation at the best dose

DNA damage and cell proliferation were evaluated by Comet assay and MTT assay

respectively. Apoptosis

mitochondrial membrane potential and cell cycle were analyzed by flow cytometry.       Results      Irradiation of 4-Gy γ-rays to osteosarcoma cells significantly reduced PNKP expression (55.17%

P0.01) and cell viability (50.16%

P0.01) compared with the Ctrl group. PNKP silencing inhibited the cell growth (inhibitory rate reached to 129.61%

P0.01) and increased DNA damage (DNA migration amount increased by 58.94%

P0.01) after irradiation. It also could arrest the cell cycle in S phase

accelerate apoptosis and reduce mitochondrial membrane potential as compared with the siCtrl+IR group.       Conclusion      PNKP silencing increases osteosarcoma cell sensitivity to radiation therapy.