AMN107 inhibits TEL-PDGFRβ in vitro. (A) Dose-dependent effects of AMN107 on growth of TEL-PDGFRβ–transformed Ba/F3 cells. Ba/F3 cells stably transduced with the indicated constructs were treated with AMN107 for 48 hours in the absence of IL-3, and the proliferation of treated cells relative to untreated cells was determined. Ba/F3 control cells were treated in the presence of IL-3. Values reflect mean of 3 samples; error bars show standard deviation. T/P indicates TEL-PDGFRβ; T/F, TEL-FGFR3. (B) Analysis of phosphorylation of TEL-PDGFRβ in response to AMN107. TEL-PDGFRβ– or TEL-FGFR3–transformed Ba/F3 cells were incubated with increasing concentrations of AMN107 in the absence of serum and IL-3, and whole-cell lysates were prepared for Western blotting with antiphosphotyrosine and anti-PDGFRβ or anti-FGFR3. (C) Analysis of phosphorylation of downstream effectors of TEL-PDGFRβ. Whole-cell lysates from Ba/F3 cells transformed with the indicated constructs were analyzed for phosphorylation of PLCγ and PI3K, downstream effectors of PDGFRβ signaling.