(A and B) WT mice were left untreated or received either PD0325901 (901, 5 mg/kg) or GDC-0941 (GDC, 100 mg/kg) by oral gavage, and were euthanized 2 or 6 hours later. Bone marrow cells were harvested and left untreated or were stimulated with GM-CSF for 10 min, and the abundances of pERK (A, left panel) and pSTAT5 (A, right panel) were determined by flow cytometric analysis. Data are representative of three mice for each time point. The red vertical lines display basal MFI values. (B) MFI plots of the data shown in (A) depict the effects of GM-CSF on pERK and pSTAT5 abundances, as well as the extent of inhibition observed in mice that were treated with the MEK inhibitor PD032501 or the PI3K inhibitor GDC-0941. Data are medians ± SD from three mice for each time point.