Radiosensitization of Osteosarcoma Cells Using the PARP Inhibitor Olaparib Combined with X-rays or Carbon Ions

Meng Dong; Hongtao Luo; Ruifeng Liu; Jinhua Zhang; Zhen Yang; Dandan Wang; Yuhang Wang; Junru Chen; Yuhong Ou; Qiuning Zhang; Xiaohu Wang

doi:10.7150/jca.90371

Radiosensitization of Osteosarcoma Cells Using the PARP Inhibitor Olaparib Combined with X-rays or Carbon Ions

J Cancer. 2024 Jan 1;15(3):699-713. doi: 10.7150/jca.90371. eCollection 2024.

Authors

Meng Dong^{1

2

3}, Hongtao Luo^{2

4

5}, Ruifeng Liu^{2

4

5}, Jinhua Zhang^{2

4}, Zhen Yang^{2

6}, Dandan Wang^{1

2}, Yuhang Wang^{1

2}, Junru Chen^{1

2}, Yuhong Ou^{1

2}, Qiuning Zhang^{2

4

5}, Xiaohu Wang^{1

2

4

5}

Affiliations

¹ The First School of Clinical Medicine, Lanzhou University, Lanzhou, China.
² Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China.
³ Clinical Medical College & Affiliated Hospital of Chengdu University, Chengdu, China.
⁴ Department of Postgraduate, University of Chinese Academy of Sciences, Beijing, China.
⁵ Heavy Ion Therapy Center, Lanzhou Heavy Ions Hospital, Lanzhou, China.
⁶ Gansu University of Chinese Medicine, Lanzhou, China.

Abstract

Objective: Osteosarcomas are derived from bone-forming mesenchymal cells that are insensitive to radiation. This study aimed to investigate the radiosensitization of osteosarcoma cells (U2OS and K7M2) using the PARP inhibitor olaparib combined with X-rays or carbon ions (C-ions). Methods: The effect of olaparib on the proliferation of osteosarcoma cells after irradiation was assessed using CCK-8 and clone formation assays. Cells were treated with olaparib and/or radiation and the effects of olaparib on the cell cycle and apoptosis were analysed by flow cytometry after 48h. Immunofluorescence was used to stain the nuclei, γ-H2AX, 53BP1, and Rad51 proteins, and the number of γ-H2AX, 53BP1, and Rad51 foci was observed under a fluorescence microscope. The effect of olaparib combined with radiation on double-stranded DNA breaks in osteosarcoma cells was evaluated. Results: At the same radiation dose, olaparib reduced the proliferation and colony formation ability of irradiated osteosarcoma cells (P < 0.05). Olaparib monotherapy induced minimal apoptotic effects and G₂/M phase arrest in osteosarcoma cells and irradiation alone induced moderate apoptosis and G₂/M phase arrest. However, radiation combined with olaparib significantly increased the percentage of apoptotic cells and G2/M phase arrest in osteosarcoma cells (P < 0.05). Immunofluorescence experiments showed that compared to the radiation group, the formation of γ-H2AX and 53BP1 foci was significantly increased in the combined group (P < 0.05). The expression levels of Rad51 foci in the irradiated group were higher than those in the control group (P < 0.05). However, the number of Rad51 foci in the combined group was significantly decreased (P < 0.05). Conclusion: The PARP inhibitor olaparib combined with irradiation (X-rays or C-ions) enhanced the radiosensitivity of osteosarcoma cell lines (U2OS and K7M2). Our findings provide a potential theoretical basis for the clinical application of olaparib in overcoming radiation resistance in osteosarcoma.

Keywords: PARP inhibitor; X-rays; carbon ion; olaparib; osteosarcoma; radiosensitization.