53BP1 loss suppresses the radiosensitizing effect of icotinib hydrochloride in colorectal cancer cells

Abstract

Background: This study aimed to investigate the influence of the expression of P53-binding protein 1 (53BP1), a key component in DNA damage repair pathways, on the radiosensitizing effect of icotinib hydrochloride in colorectal cancer and to elucidate the mechanisms underlying this influence.

Materials and methods: Real-time RT-PCR and Western blotting were performed to verify the gene-knockout effect of 53BP1 small hairpin RNA (ShRNA), and colony formation assay was employed to investigate the influence of 53BP1 downregulation on the radiosensitizing effect of icotinib hydrochloride in HCT116 cells. Cell apoptosis, cell cycle distributions, and histone H2AX (γ-H2AX) fluorescence foci after 53BP1 knockdown were evaluated. Relative protein expression in the ataxia telangiectasia mutated kinase (ATM)-checkpoint kinase-2 (CHK2)-P53 pathway was measured by Western blot analysis to unravel the molecular mechanisms linking the pathway to the above phenomena.

Results: Icotinib hydrochloride increased the radiosensitivity of HCT116 cells; however, this effect was suppressed by the downregulation of 53BP1 expression, a change that inhibited cell apoptosis, increased the percentage of HCT116 cells arrested in S-phase and inhibited the protein expression of key molecules in the ATM-CHK2-P53 apoptotic pathway.

Conclusion: Our studies confirmed that the loss of 53BP1 serves as a negative regulator of the radiosensitizing effect of icotinib in part by suppressing the ATM-CHK2-P53 apoptotic pathway.

Keywords:

• 53BP1
• colorectal cancer
• DNA damage repair
• icotinib hydrochloride
• radiosensitivity

Disclosure statement

All authors declare that they have no conflicts of interest.

Additional information

Funding

This study was approved by the Natural Science Foundation of Hubei Province of China [Grant No. 2015CFB659].

Notes on contributors

Ai Huang

Ai Huang, M.D, is an oncological resident, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Jing Yao

Jing Yao, Ph.D, is a current associate professor, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Tao Liu

Tao Liu, M.D, is an oncological resident, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Zhenyu Lin

Zhengyu Lin, Ph.D, is an oncological resident, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Sheng Zhang

Sheng Zhang, M.D, is an associate professor and associate chief leader of radiation department, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Tao Zhang

Tao Zhang, Ph.D, is a current professor and chief leader of abdominal oncology department, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Hong Ma

Hong Ma, Ph.D, is an associate professor and an oncological and radiological associate chief physician with a specific interest and expertise in gastrointestinal cancer, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.