Inhibition of cytokine-mediated proliferation of 32Dβ cells by CP-690,550 showed specificity for the γc/Jak3/STAT5-signaling pathway. (A) After cytokine starvation for 24 hours, 32Dβ cells were stimulated with human IL-2 or murine IL-3 for 48 hours with and without CP-690,550. 3H-thymidine was added during the last 6 hours of the cultures. Cells were then harvested and analyzed for 3H-thymidine incorporation. (B) After cytokine starvation for 24 hours, 32Dβ cells were stimulated with 1 μg/mL of human IL-2 or 10 ng/mL of murine IL-3 for 2 hours with and without the addition of CP-690,550. The cell lysates were immunoblotted with an anti–phospho-STAT5 monoclonal antibody and an anti-STAT5 antibody. β-Actin was used as an input control. Data are presented as means ± SD (A) and are representative of 3 independent experiments.
