Fig. 4. A moderate level of SOCS3 expression blocks growth inhibition but not protection against apoptosis by IL-9. BW5147 cells ectopically expressing a moderate level of SOCS3 (30) were transfected with hIL-9R in the pEF-myc-cyto plasmid. Clones expressing a similar level of receptor were used. A, phosphorylation of each STAT after IL-9 stimulation was tested by Western blot. B, cells were stimulated with human IL-9 (1000 cells/well). After 3 days, proliferation was evaluated by measuring [3H]thymidine incorporation. C, cells were grown for 24 h with dexamethasone (100 ng/ml) and cyclosporine A (500 ng/ml) in the presence () or absence () of hIL-9 (100 units/ml). The percentage of apoptotic cells was measured by flow cytometry after propidium iodide staining (6) .