JAK/STAT signaling is enhanced in AE9a leukemia cells. (A) Flow cytometric analyses of phosphorylated JAK2 (pY1007/1008), (B) STAT3 (pY705), and (C) STAT5 (pY694) in the Lin⁻/cKit⁺ population of wild-type bone marrow and AE9a leukemia blood, spleen, and bone marrow. Phosphorylated STAT5 was detected after stimulation with cytokines (100 ng/mL Flt3 ligand, 100 ng/mL stem cell factor, 20 ng/mL IL-3, 20 ng/mL IL-6, and 20 ng/mL G-CSF) for 15 minutes. Representative results from 6 wild-type samples and 7 leukemia mice are shown.