The effect of rapamycin and dexamethasone on cell cycle regulatory proteins. (A) Exponentially growing MM cells were harvested, and total RNA was isolated. RPA was performed by using the multiprobe template hCYC-1. (B-C) Karpas 707 cells or (D-E) U-1958 cells were treated with either (B,D) rapamycin for 6, 24, and 48 hours or (C,E) rapamycin and/or dexamethasone for 24 hours. Cells were lysed and extracts were analyzed by Western blotting by using antibodies specific for p21, p27, and the cyclins A, B, D2, D3, and E.