Evaluation of the effect of 5-FU and PTX combinations in MDA-MB-231, MDA-MB-453, and MDA-MB-436 cells. (A) MDA-MB-231, MDA-MB-453, and MDA-MB-436 cell viability after treatment with different combinations of 5-FU and PTX. * p < 0.05, ** p < 0.01; # p < 0.05, ## p < 0.01. (B) Isobologram plots for combination treatments of 5-FU and PTX in MDA-MB-231, MDA-MB-453, and MDA-MB-436 cells. Lower left of the hypotenuse, synergism; on the hypotenuse, additive effect; upper right, antagonism. (C) CI values for MDA-MB-231, MDA-MB-453, and MDA-MB-436 cells. 5-FU, 5-fluorouracil; PTX, paclitaxel; 5-FU/PTX, mechanically mixed free 5-FU and free PTX; CI, combination index.