Ethanol decreases radiosensitivity of human breast cancer MCF-7 cells

Objective: To investigate the effect of ethanol on radiosensitivity of human breast cancer MCF-7 cells. Methods: Human breast cancer MCF-7 cells were divided into four groups including control group,ethanol treatment group, X-ray exposed group,and ethanol combined with X-ray group. Clonogenic assay was used to determine cell survival. Flow cytometry was employed to analyze cell cycle progression. Annexin V-FITC kit was used to determine cell apoptosis induction.Results Ethanol (50 and 100 mmol/L, 50 h) had no influence on MCF-7 cell growth (t=0.82, 1.15, P>0.05). The radiosensitivity of MCF-7 cells was reduced when the cells were pretreated with 50 mmol/L ethanol (t=4.15, P<0.05) and 100 mmol/L ethanol (t=10.28, P<0.05) for 2 h. Compared with irradiation with X-ray alone, ethanol treatment decreased G₂/M phase arrest (t=7.18, P<0.05) and sub-G₁ population (an indicator of apoptosis induction) (t=5.39, P<0.05). A decrease of advanced and early apoptosis in the cells pretreated with ethanol was also confirmed by Annexin V-FITC apoptosis assay (t=4.86, 7.59, P<0.05). Conclusions: Ethanol causes radioresistance in human breast cancer MCF-7 cells, where the decreases of radiation-induced G₂/M phase arrest and apoptosis may be involved. (authors)