Background and Objectives:Secondary metabolites in the supernatants of probiotic microorganisms have shown anticancer effects. The present study was aimed to investigate the cytotoxicity of Bacillus coagulans supernatants and their role in apoptosis induction in MCF7 cancer cells.Materials and Methods:The inhibition of MCF7 cancer cells by Bacillus coagulans supernatants was assessed by MTT assay at three exposure times of 24, 48, and 72 h. Apoptosis induction was explored by flow cytometry while the expression levels of bax, caspase 3, caspase 9, and bcl2 were examined by real-time PCR and compared with normal HFF cells.Results:Bacillus coagulans supernatants exhibited inhibitory effects on MCF7 cells in a concentration-dependent and time-dependent manner; while lower cytotoxic effects were observed in normal HFF cells. The increase in the expression of bax, caspase 3, and caspase 9 genes and the decrease in the anti-apoptotic gene of bcl2, along with the flow cytometry results, confirmed the induction of apoptosis in the cancer cells.Conclusion:Regarding the cytotoxic influence of Bacillus coagulans supernatants against breast cancer cells, this bacterium can be considered as a potential candidate for a novel therapeutic strategy with lower side effects which of course requires further investigations.