FL impairs the cytotoxic effects of FLT3 inhibitors in primary AML samples. Five different primary AML blast samples, each harboring a FLT3/ITD mutation, were incubated in culture medium with increasing concentrations of the indicated drugs for 48 hours in the presence of FL, as in Figure 3. Cell viability was then determined using the MTT assay. Results are plotted as percentage DMSO control. Each point represents the average of quadruplicate optical density measurements. The error bars were omitted for figure clarity but, for each point, amounted to < 5% of the optical density value.