CHIR-258 inhibits FGF-mediated ERK1/2 phosphorylation and induces apoptosis of FGFR3-expressing human myeloma cell lines. (A) Flow cytometry analyses of ERK1/2 phosphorylation. Cells were serum-starved overnight (gray shaded curve) then stimulated with aFGF (dashed line), or starved overnight and pretreated for 2 hours with 100 nM (dark gray line) or 500 nM (black line) CHIR-258 and then stimulated with aFGF. (B) Cells were incubated with vehicle (□) or 100 nM (▦) or 500 nM (▧) CHIR-258 for 96 hours and apoptosis was assessed by means of flow cytometric assay of annexin V binding and propidium iodide exclusion. Values represent the mean ± SD of 4 independent experiments.