ETP-ALL hypersensitivity to IL7 stimulation. (A) Phosphoflow cytometry analysis of levels of pSTAT5 in xenografted non-ETP T-ALL and ETP-ALL leukemic blasts in the basal state (shaded) and in response to stimulation with 100 ng/mL IL7 for 15 minutes (unshaded). (B) Quantitation of mean fluorescence intensity (MFI) in the basal state and in response to IL7 exposure. (C) Change in pSTAT5 MFI with IL7 exposure compared with vehicle treatment of each xenograft. The nonparametric Mann Whitney test was used to evaluate statistical significance.