The effect of rapamycin and dexamethasone on phosphorylation of p70S6K at Thr389 and Thr421/Ser424. (A) Karpas 707 cells were treated with rapamycin and/or dexamethasone. At 0, 6, and 24 hours cells were lysed, and extracts were subjected to analysis by Western blotting using antibodies specific for the p70S6K phosphorylation sites Thr389 and Thr421/Ser424. (B) Karpas 707 cells were treated with dexamethasone at indicated times followed by Western blotting analysis of p70S6K phosphorylation as described earlier.