AG1296, PKC412, and SU5614 inhibit FLT3-mediated STAT5 phosphorylation. Mutant FLT3-expressing Ba/F3 cells were incubated with the indicated concentrations of (A) AG1296, (B) PKC412, and (C) SU5614 or vehicle alone for 4 hours prior to cell lysis. Parental Ba/F3 cells were treated likewise but in the presence of IL-3. Activation of STAT5 was demonstrated by immunoblotting the total cell lysates with anti-pSTAT5 antibody (upper panel). After stripping the membrane was reprobed with total anti-STAT5 antibody (lower panel). Optical density (OD) ratios of STAT5 phosphorylation of treated versus untreated cells are shown below the upper panel.