Breast cancer cells treated with 267 and docetaxel combined at a fixed ratio and added at various concentrations exhibit synergistic effects based on a measured cell viability endpoint. (a) LCC6 and (b) LCC6Her2 cells were treated with increasing concentrations of 267, docetaxel (Dt) or 267 and Dt combined at a fixed ratio (50 μm:1 nm). Percentage cell viability relative to control cells not treated with drugs (100% viable) are shown and each data point is the average (± standard deviation) of triplicate samples. Combination index (CI) values determined by Calcusyn from dose-response curves of (c) LCC6 and (d) LCC6Her2 cells treated with 267/Dt combinations. Data points represent the average (± standard deviation) from triplicate experiments. CI values less than one are indicative of synergistic effects; CI values greater than one are indicative of antagonistic effects; and CI values equal to one are indicative of additive effects. Fraction affected (FA) is a measure of the determined effect (cytotoxicity as measured by an Alamar blue assay) and amount of drug to achieve a FA of 0.5 is referred as the ED50. (e) Mean CI values at ED50 for LCC6, LCC6Her2, MCF-7, MDA MB468, KPL-4, and SKBR-3 cells treated with 267 and Dt combined are shown and each data point represents the average (± standard deviation) from triplicate experiments.