Effect of poly adenosine diphosphate ribose polymerase inhibitor on the radiosensitivity of breast cancer cells and underlying mechanism / 中华放射医学与防护杂志

ABSTRACT

Objective:To study the effects of poly adenosine diphosphate ribose polymerase (PARP) inhibitors niraparib and pamiparib on the radiosensitivity of breast cancer cell lines MCF-7 and MDA-MB-436, and to explore its mechanism.Methods:MCF-7 and MDA-MB-436 cells were divided into control group, niraparib group, pamiparib group, radiation group, combination group treated with niraparib and radiation, and combination group treated with pamiparib and radiation, respectively. The effects of drugs on cell proliferation and radiosensitivity were measured by CCK-8 assay and colony formation assay, respectively. The effect of drugs combined with radiation on cell cycle and apoptosis were detected by flow cytometry. Immunofluorescence method was used to detect the changes of γ-H2AX focal number of cells. The expressions of FANCG, Bax and Bcl-2 mRNA and protein were detected by qPCR and Western blot, respectively.Results:Both niraparib and pamiparib inhibited the proliferation of breast cancer cells MCF-7 and MDA-MB-436 in a time-dose dependent manner. With the increase of irradiation dose, D0, Dq, SF2 value of MCF-7 and MDA-MB-436 cells decreased, and SER D0 and SER Dq value increased. Compared with control group, the percentages of cells in G 2/M phase were increased ( tMCF-7=41.66, 44.08, P<0.05; t436=24.69, 18.91, P<0.05), the percentage of cells in G 0/G 1 phase were decreased ( tMCF-7=8.67, 29.61, P<0.05; t436=26.39, 29.12, P<0.05), and the cell apoptosis rate was significantly increased ( tMCF-7=11.17, 11.71, P<0.05; t436=42.68, 15.89, P<0.05) in the combination group. Compared with control group, the number of γ-H2AX foci of MCF-7 cells in the radiation group and combination group treated with niraparib and radiation increased significantly at 2 h after irradiation ( t=8.89, 21.72, P<0.05). At 24 h after irradiation, the number of γ-H2AX foci basically returned to normal level in the radiation group but remained at a higher level in the combination group ( t=8.82, P<0.05). Compared with control group, the expressions of FANCG and Bcl-2 mRNA decreased ( tFANCG=14.07, P<0.05; tBcl-2=29.21, P<0.05), the expression of Bax mRNA increased ( t=8.90, P<0.05), and the expression of FANCG and Bcl-2 proteins decreased ( tFANCG=7.09, P<0.05; tBcl-2=10.24, P<0.05), while the expression of Bax protein increased ( t=2.90, P<0.05) in the combination group. Conclusions:PARP inhibitors niraparib and pamiparib can increase the radiosensitivity of breast cancer MCF-7 and MDA-MB-436 cells probably through down-regulating the expression of FANCG in FA-BRCA pathway, up-regulating apoptosis-related genes and inhibiting DNA damage repair.