Estrogen receptor mediates the radiosensitivity of triple-negative breast cancer cells

Abstract

Background: This study aimed to evaluate differences in the radiosensitivities of triple-negative breast cancer (TNBC) and luminal-type breast cancer cells and to investigate the effects of estrogen receptor (ER) expression on the biological behaviors of the cells. Material/Methods: Colony-forming assays were performed to detect differences in radiosensitivities in breast cancer cell lines. Gene transfection technology was used to introduce the expression of ERa in TNBC cells to compare the difference in radiosensitivity between the TNBC cells and ERa transfected cells. CCK-8 assays were used to observe changes in the proliferation of TNBC cells after ERa transfection. Immunofluorescence was used to detect the number of gH2AX foci in nuclei. Flow cytometry was used to detect changes in cell cycle distribution and apoptosis. Western blotting was used to detect changes in autophagy-associated proteins. Results: The radioresistance of the TNBC cell line MDA-MB-231 (231 cells) was greater than that of ERa-positive luminal-type breast cancer cell line MCF-7. Moreover, 231 cell proliferation and radioresistance decreased after ERa transfection. Interestingly, ERa-transfected 231 cells showed increased double-stranded breaks and delayed repair compared with 231 cells, and ERa-transfected 231 cells showed increased G2/M phase arrest and apoptosis after irradiation compared with those in 231 cells. ERa transfection in 231 cells reduced autophagy-relat-ed protein expression, suggesting that autophagy activity decreased in 231 ER-positive cells after irradiation. Conclusions: TNBC cells were more resistant to radiation than luminal-type breast cancer cells. ERa expression may have major roles in modulating breast cancer cell radiosensitivity.