Fig. 5

Cytotoxicity assays of DE and DAES with or without SO1861. Cytotoxicity of DE and DAES was evaluated by incubation of HCT 116 (EGFR-positive) and MDA-MB-453 (low EGFR-expression) cells with different concentrations of the toxins ranging from 0.1 pM to 1 μM, with or without addition of SO1861 at a concentration of 125 μg/mL. After 48 h incubation, the viability of the cells was measured by MTT assay. a1 The curves result from four parameter logistic regression by GraphPad Prism. The 95% confidence interval for each curve is indicated. The displayed data points each represent the mean ± SEM of three or four independent assays each performed in triplicate. As an exception, the two data points of DE at a concentration of 100 nM and 1 μM with addition of SO1861 rely on only two experiments. a2 Overview over IC₅₀-values for HCT 116 cells, including 95% confidence interval and statistical significance. A logarithmic scale is used for the y-axis. Statistical significance was assessed by Student’s unpaired t-test. P < 0.05 was required for statistical significance. P < 0.05, *; P < 0.01, **; P < 0.001, ***. b The curves result from four parameter logistic regression by GraphPad Prism. The 95% confidence intervals could not be calculated because the sigmoid curves did not reach the baseline level due to the low toxicity for MDA-MB-453 cells. The displayed data points each represent the mean ± SEM of three or four independent assays each performed in triplicate. Additional graphs that allow ideal comparison of the effect on HCT 116 cells with the effect on MDA-MB-453 cells can be found in Additional file 8