ObjectiveTo explore the effects of long non-coding RNA neighbour of BRCA1 gene2(NBR2) on the radiosensitivity of breast cancer MCF-7 and MDA-MB-231 cells.

MethodAccording to different treatment methods, breast cancer MCF-7 and MDA-MB-231 cells were divided into the following groups:(1) three groups including control group, 4 Gy γ ray irradiation group, and 8 Gy γ ray irradiation group, then the expression level of NBR2 was tested by real-time quantitative PCR(qRT-PCR) analysis; (2) four groups including control group, NBR2 transfection group, 4 Gy γ ray irradiation group, and NBR2 transfection+γ ray irradiation group, then the proliferation of breast cancer MCF-7 and MDA-MB-231 cells was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide(MTT) assays; (3) three groups including control group, NBR2 transfection group, and NBR2+B-cell lymphoma-2(BCL2) transfection group, and the cells were irradiated with different doses of γ ray, then the proliferation was detected by MTT and clonogenic assay. Statistical significance of the results was determined by SPSS statistical software and analyzed by student's t-test. P<0.05 was considered statistically significant.

ResultsqRT-PCR analysis revealed that compared with that in the control group, the expression of NBR2 was decreased significantly in breast cancer MCF-7 and MDA-MB-231 cells treated with γ ray irradiation(MCF-7:t=10.75, 11.17, MDA-MB-231:t=11.22, 12.31, all P<0.01). MTT assays showed that compared with the cells irradiated alone, the breast cancer MCF-7 and MDA-MB-231 cells irradiated in the presence of NBR2 had significantly decreased proliferation (MCF-7: t=10.55, MDA-MB-231:t=11.97, both P<0.01). NBR2 could also down-regulate the mRNA and protein level of BCL2 in these cells. The enhanced BCL2 expression significantly reduced the NBR2 inhibition of breast cancer MCF-7 and MDA-MB-231 cell proliferation after irradiation as compared with that of NBR2 alone (MCF-7:t=10.87, MDA-MB-231:t=11.37, both P<0.01).

ConclusionsIrradiation could decrease the expression level of NBR2. The overexpression of NBR2 could down-regulate the BCL2 level and suppress the proliferation of breast cancer MCF-7 and MDA-MB-231 cells, thus enhancing the radiosensitivity of breast cancer cells.