IMC-EB10 inhibits phosphorylation of downstream MAP kinase induced by wild-type FLT3 or FLT3-ITD. (A) EOL-1 and (B) EM3 cells were incubated with varying amounts of antibody with or without exogenous FL (30 ng/mL). MAPK was phosphorylated after FL stimulation (lanes 1 and 2 from right). Control antibody treatment did not affect MAPK phosphorylation (lane 8 from right). In contrast, treatment with IMC-EB10 (1-200 nM) completely inhibited FL-induced MAPK phosphorylation. (C) BaF3-ITD and (D) MV4;11 cells were incubated in varying concentrations of antibody without exogenous FL. Lane 1 (from right) indicates that MAPK was constitutively phosphorylated. Treatment with control antibody did not affect ligand-independent constitutive MAPK phosphorylation (lane 8 from right). In contrast, constitutive MAPK phosphorylation was inhibited by IMCEB10. Total MAPK protein was unaffected by antibody treatment.