MTT assay

To investigate the effect of cisplatin, BC-MSC-CM combination cisplatin on the viability of MCF-7 cells, an MTT assay was performed. Briefly, MCF-7 cells were plated at a density of 1×10⁴ cells/well in a 96-well rounded bottom plate. After incubation for 12 h, cells were incubated with cisplatin for another 48 h at 37°C by a continuous induction from 2.5 to 80 µM (2.5, 5, 10, 20, 40 and 80 µM) in a stepwise increasing concentration manner in the presence or absence of BC-MSC-CM. Control medium was used as a control. All the cells were cultured for a further 48 h. Subsequently, MTT reagent was added into each well and the cells were incubated for an additional 4 h at 37°C. Following incubation and removal of the supernatant, 150 µl DMSO was added to dissolve the dye and the absorbance was measured at 490 nm with a microplate reader. IC₅₀ was defined as the drug concentration causing a 50% apoptosis relative to the negative control. In this experiment, the IC₅₀ was 20 µM. The experiment was repeated three times; six parallel samples were detected each time.