Abstract: Objective To investigate the effect of salinomycin（Sal） on the proliferation and apoptosis of triple negative breast cancer cell line MDA-MB-231 and its mechanism. Methods The flow cytometry was used to screen ALDH highly expressed breast cancer cell lines，and MTT method was used to detect the effect of different concentrations of Sal（1-32 μmol/L） on cell proliferation. The flow cytometry was used to detect the effect of Sal on apoptosis and the expression of ALDH on tumor stem cell surface，qPCR and Western blot were used to detect the mRNA and protein expression of apoptosis-related molecules Caspase-3，Bax，Bcl-2 and PARP. The data of breast cancer patients were downloaded from the Cancer Genome Atlas （TCGA） database（n=1 218），and Pearson method was used to analyze the correlation between ALDH and apoptosis-related molecules expression. Results Sal could inhibit the proliferation of MDA-MB-231 cells in a dose-dependent manner at 24 h，48 h，and 72 h（all P<0.001）. Compared with the control group，the apoptosis rates of the 2 μmol/L group，4 μmol/L group and 8 μmol/L group increased after Sal acting on MDA-MB-231 cells for 48 h（all P<0.05），and the mRNA expression of Bcl-2，PARP and Caspase-3 decreased （all P<0.05），while the mRNA expression of Bax increased（all P<0.05）；the protein expression of Bcl-2 and Caspase-3 decreased（all P<0.05），while the protein expression of PARP and Bax increased（all P<0.05）； the expression of ALDH，a surface marker of tumor stem cells decreased（P<0.05）. TCGA database analysis showed that ALDH was positively correlated with the expression of anti-apoptotic molecules Bcl-2 and Caspase-3（r=0.209，P=0.007；r=0.235，P=0.002），whereas negatively correlated with the expressions of Bax and PARP（r=-0.326，P<0.001； r=-0.453，P<0.001）. Conclusion Sal can inhibit the growth of human breast cancer cell line MDA-MB-231，possibly by down-regulating the expression of ALDH，a surface marker of tumor stem cells.

Key words: Breast cancer, Salinomycin, Proliferation, Apoptosis, ALDH