Figure 3.

A. Antagonistic effect of doxorubicin on rottlerin. Sigmoidal inhibition curves for MCF-7 cells treated either with doxo or rottlerin, or with the two drugs together in a constant ratio of 1:10. The IC₅₀ were calculated by nonlinear regression, using Graphpad Prism software. As shown by the dashed line, doxo antagonizes the action of rottlerin, producing a shift to the left of its curve. B. Graphic representation of the combination index calculated following the Loewe model. The combination index of the rottlerin-doxorubicin mixture, never goes below the additivity reference line of one, indicating that doxorubicin and rottlerin have antagonistic effects. All the experiments were performed in quadruplicate and repeated at least twice.