1. PLK1 Inhibition Sensitizes Breast Cancer Cells to Radiation via Suppressing Autophagy
- Author
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Huiping Liang, Zixu Mao, Quanquan Sun, Meiling Ai, Yawei Yuan, Muhammad Khan, Hongli Yang, Xiaoting Huang, Zhaoze Guo, Baiyao Wang, Jiang Zhang, Ronghui Zheng, and Yunhong Tian
- Subjects
Radiation-Sensitizing Agents ,Cancer Research ,Cell ,Apoptosis ,Breast Neoplasms ,Cell Cycle Proteins ,Protein Serine-Threonine Kinases ,Radiation Tolerance ,030218 nuclear medicine & medical imaging ,Flow cytometry ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Breast cancer ,Cell Line, Tumor ,Proto-Oncogene Proteins ,Autophagy ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,Radiosensitivity ,Protein Kinase Inhibitors ,Cell Proliferation ,Radiation ,medicine.diagnostic_test ,business.industry ,Kinase ,Cell growth ,Cancer ,Cell cycle ,medicine.disease ,medicine.anatomical_structure ,Oncology ,030220 oncology & carcinogenesis ,Cancer research ,business - Abstract
Purpose Polo-like kinase 1 (PLK1) is a protein kinase that is overexpressed in breast cancer and may represent an attractive target for breast cancer treatment. However, few studies have investigated the relationship between PLK1 and radiosensitivity in breast cancer. Here, we attempted to explore whether PLK1 inhibition could sensitize breast cancer cells to radiation. Methods and Materials Breast cancer cells were treated with PLK1 small interference RNA or the PLK1-inhibitor, GSK461364. Cell proliferation was assessed using a colony formation assay. Cell cycle analyses were performed by flow cytometry. DNA damage, autophagy, and reactive oxygen species induced by ionizing radiation were detected by immunofluorescence, Western blot, and flow cytometry, respectively. Microtubule-associated protein 1 light chain 3 alpha (LC3) puncta were detected using an immunofluorescence assay. A clonogenic survival assay was used to determine the effect of PLK1 inhibition on cell radiosensitivity. A xenograft mouse model of breast cancer cells was used to investigate the potential synergistic effects of PLK1 inhibition and irradiation in vivo. Finally, the expression of PLK1 and LC3 in the breast cancer tissues was evaluated by immunohistochemistry. Results PLK1 inhibition significantly suppressed the proliferation and increased the radiosensitivity of breast cancer cells. Pharmacologic inhibition of PLK1 by the selective inhibitor, GSK461364, enhanced the radiosensitivity of breast cancer cells in vivo (n = 4, P = .002). Mechanistically, PLK1 inhibition led to the downregulation of radiation-induced reactive oxygen species and autophagy, thereby increasing the radiosensitivity of breast cancer cells. Additionally, we detected a positive correlation between the expression of PLK1 and LC3 in human breast cancer samples (n = 102, R = 0.486, P = .005). Conclusions Our findings indicate that PLK1 inhibition enhances the radiosensitivity of breast cancer cells in a manner associated with the suppression of radiation-induced autophagy. The inhibition of PLK1 represents a promising strategy for radiosensitizing breast cancer.
- Published
- 2021
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