STAT5 inhibition abrogates IL-7–mediated upregulation of CD71, and downregulation of p27^kip1, but not upregulation of Bcl-2 in T-ALL cells. IL-7-deprived TAIL7 or primary T-ALL cells were cultured for 72 hours in medium, IL-7, or IL-7 plus S5i, and analyzed for CD71 surface expression (A-B), expression of p27^kip1 (C), and Bcl-2 levels (D-E). Mean fluorescence intensity (MFI) values are indicated for each flow cytometry histogram. Vertical lines indicate peak value in medium alone. (F) Under the same experimental conditions, TAIL7 cells were collected at 24 hours, and BCL2 transcript levels determined by qPCR. Fold induction is normalized to the medium alone. Results are representative of at least 2 independent experiments or 3 patients. Graphics represent average of triplicates ± SEM. **P < .01; ***P < .001. ns, not significant (P ≥ .05).