FL impairs inhibition of FLT3 autophosphorylation in vitro. (A) Molm14 cells were exposed to increasing concentrations of lestaurtinib in the presence of 0, 1, and 3 ng/mL of FL in plasma for 2 hours. FLT3 autophosphorylation was then evaluated by immunoblotting (gels, left) by immunoprecipitating FLT3, and then, after electrophoresis and transfer to membrane, probing with antiphosphotyrosine. The bands were analyzed by densitometry and plotted (graph, right). (B) Molm14 cells were incubated in plasma with 10μM of the indicated drug and 0 ng/mL (−) or 3 ng/mL (+) of FL for 2 hours. FLT3 autophosphorylation was then evaluated by immunoblotting.