GM-CSF–dependent pSTAT5 hypersensitivity is cytokine-specific. (A) Representative flow dot plots from CMML samples stimulated with GM-CSF, IL-3, or G-CSF at 0.01, 0.1, 1, and 10 ng/mL. The percentage of pSTAT5-positive cells is indicated in each dot plot. (B) Representative colonies in methyl cellulose generated after treatment with G-CSF, IL-3, and GM-CSF at 10 ng/mL alone. (C) Percentage and (D) 95th FI of pSTAT5-positive cells from CMML patients treated with increasing doses (0.01, 0.1, 1, and 10 ng/mL) of GM-CSF, IL-3, or G-CSF. All pSTAT5 flow cytometry data are expressed as fold change from the cohort’s highest pSTAT5 level. Data were normalized using square root transformation. Significant P values are indicated using linear regression analysis.