Fig. 1

Evaluation of the cytotoxicity of salinomycin (Sal) and dasatinib (Das) as single drugs or a 2-drug combination on MDA-MB-468, MDA-MB-231, and MCF-7 cell lines (monolayer cell culture system) and tumor spheroids. a Chemical structures of the drugs. b A comparison of the potencies of individual drugs. To measure cell viability, different human BC cell lines, cultured in monolayers, were incubated with the drugs at various concentrations for 72 h. The results were fit into sigmoidal dose response curves for calculating the IC₅₀ values. c A table summarizing the specific IC₅₀ values of both Sal and Das. Sal was more potent than Das regardless of the cell line tested. d A table summarizing the synergism of the same drug combination but different applied drug ratios of Sal and Das for treating various BC cell lines. Drug combinations had a stronger synergistic effect on MDA-MB-468, as shown by the lower CI₉₅ values. The CI₉₅ values were determined using the previously described Chou-Talalay method [6]. Note that CI₉₅ represents the specific CI value where there is a 95% cell growth inhibition. e A schematic diagram showing the method for preparing tumor spheroids. f Representative microscopic images of the MDA-MB-468, MDA-MB-231, and MCF-7 spheroids. Scale bar is 200 μm. g The cytotoxic effect of the drugs alone. The spheroids were treated with drugs at various concentrations for 72 h. The results from the viability assays were fit into sigmoidal dose response curves for determining the IC₅₀ values. h A table summarizing the specific IC₅₀ values of Sal and Das tested on different tumor spheroids. i A comparison of the synergism of different drug combination regimens, applied concurrently at different drug ratios, for eradicating the spheroids. All the experiments were independently performed in triplicate