Radiosensitivity Of Human Breast Cancer MCF-7 Cells To Heavy Ion Radiation And The Underlying Mechanism

Objective:The aim of this study was to compare the different radiosensitivity of human breast cancer MCF-7 cells to heavy ion radiation and X-rays,and to explore the underlying molecular mechanisms of radiosensitivity in MCF-7 cells.Methods:MCF-7 cells were irradiated with X-rays and carbon ions（2 Gy,4 Gy and 8 Gy）,respectively.The proliferation of MCF-7 cells was detected by CCK-8assay at 24 h,48 h and 72 h after irradiation.The survival rate of MCF-7 cells was examined by colony survival experiments.The cell cycle distribution and apoptotic rates of MCF-7 cells were analyzed by flow cytometry.The expression ofγ-H2AX,CyclinB1,Bax,Bcl-2 and related proteins in Akt/mTOR/p70S6K signaling pathway were detected by Western blotting.Results:Both X-rays and carbon ions can inhibit the proliferation and colony formation of MCF-7 cells in a dose-dependent manner,and induce G₂/M phase arrest and apoptosis in MCF-7 cells.Compared with the same dose of X-ray,carbon ions can significantly inhibit the proliferation and colony formation of MCF-7 cells,and significantly increase the G₂/M phase arrest and apoptotic rates of MCF-7 cells.The results of Western blotting showed that compared with the same dose of X-ray,carbon ions can significantly increase the expression ofγ-H2AX and Bax protein,significantly reduce the expression of CyclinB1 and Bcl-2 proteins,indicating that carbon ions caused more serious DNA damage and apoptotic effects than X-ray.Compared with the same dose of X-ray,carbon ions can significantly reduce the phosphorylation levels and the expression level of Akt,mTOR and p70S6K.Conclusion:The radiosensitivity of MCF-7 cells to carbon ions is higher than that of X-rays.The mechanism may be related to the stronger DNA damage and apoptotic effects of carbon ions,and the inhibition of Akt/mTOR/p70S6K signaling pathway by carbon ions.