Fig. 5

Cell viability following doxorubicin treatment alone or combined with 1.0 μM of either masitinib or imatinib. Graphical plot of the effects of treatment with escalating concentrations of doxorubicin alone or combined with 1.0 μM of either masitinib or imatinib on viability of (a) MBSa1 and (b) CoFSA cells. Cell viability was assessed using a MTS assay following treatment with the above drug concentrations after 72 h of incubation. Masitinib showed a synergistic interaction with doxorubicin at all concentrations for MBSa1 and at 10, 300, 1000, and 3000 nM for CoFSA. Imatinib showed a synergistic interaction with doxorubicin at 1, 3, 10, 30, and 100 nM for MBSa1 and at 300, 1000, and 3000 nM for CoFSA. Plotted values are mean ± standard error of the mean. Synergism was defined as being present when the surviving fraction of cells exposed to the combination of doxorubicin and either tyrosine kinase inhibitor was lower than the product of the surviving fraction of cells exposed to the tyrosine kinase inhibitor alone multiplied by the surviving fraction of cells exposed to doxorubicin alone. See Materials and Methods section for detailed synergism calculation methods