Function and mechanism of combined PARP-1 and BRCA genes in regulating the radiosensitivity of breast cancer cells.

Objective: To study the function and mechanism of combined PARP-1 and BRCA genes in regulating the radiosensitivity of breast cancer cells by poly ADP-ribose polymerase-1 (PARP-1) inhibitor 3-amion benzamide (3-AB) onBRCA mutant and non-mutant breast cancer cells. Methods: Four groups of BRCA mutant cells MDA-MB-436 and BRCA non-mutant cells MDA-MB-231 were divided respectively into control (CTRL), ionizing radiation alone (IR), 3-AB alone (3-AB), and ionizing radiation combined with 3-AB (IR+3-AB) groups. The γ-H2AX foci were detected by immunofluorescence assay to show the DNA double-strand damage. The clonogenic cell survival assay was applied to evaluate the radiosensitivity of breast cancer cells, and flow cytometry was used to assess the percentage of apoptosis cells. Results: The apoptosis rate of MDA-MB-436 cells was significantly increased compared with MDA-MB-231 cells treated with irradiation, and 3-AB could further enhance the effect. Similarly, the result of γ-H2AX foci detection showed that DNA double-stranded damage of the MDA-MB-436 cells was significantly greater than that of MDA-MB-231 cells (t = 4.57, P < 0.05), and the DNA damage of MDA-MB-436 cells in IR+3-AB group was the most remarkable. The difference was significant (t = 3.26, P < 0.05). In the same group, compared with MDA-MB-231 cells, MDA-MB-436 cells had the significantly greater apoptosis rate (t = 2.96, P < 0.05). The apoptosis rate of MDA-MB-436 cells in the IR+3-AB group showed by flow cytometry was highest (t = 3.81, P < 0.05). Conclusions: Compared with non-BRCA mutant MDA-MB-231 cells, the BRCA mutant breast cancer MDA-MB-436 cells could incur significantly greater DNA damage, and therefore the radiosensetivity of MDA-MB-436 cells is higher than that of MDA-MB-231 cells. The inhibitor of PARP-1, which can block the repair of single-strand damage caused by radiation, can further enhance the level of apoptosis and radiosensitivity of BRCA-mutant cells.