Abstract:

Objective To investigate the effects of different ionizing radiation doses on DNA damage and apoptosis of breast cancer cell lines with and without BRCA mutations. Methods BRCA mutant cells （MDA-MB-436） and non-BRCA mutant cells （MDA-MB-231） were subjected to different doses of ionizing radiation：0，2，4，6，8，or 10 Gy. The percentage of apoptotic cells was assessed by flow cytometry. After 30 min of irradiation， DNA damage was detected using an immunofluorescence-based γH2AX focus assay. Results Increasing radiation dose was associated with greater double-strand DNA damage and apoptosis in both MDA-MB-436 and MDA-MB-231 cells，with the greatest effects reached at 8 Gy. At individual doses，DNA damage and apoptosis were significantly more severe in MDA-MB-436 cells than in MDA-MB-231 cells（P＜0.05）. Conclusions Double-strand DNA damage and apoptosis vary in proportion to radiation dose， and cells containing BRCA mutations may be more radiation-sensitive than cells lacking such mutations.

Key words: Breast neoplasm, Ionizing Radiation, Apoptosis, DNA damage, BRCA gene, mutation