CHIP and c-Cbl induce degradation of BCR-ABL leading to attenuation of BCR-ABL–dependent cell growth. (A) BCR-ABL–expressing Ba/F3 cells with the tet regulatory expression system for CHIP and c-Cbl were deprived of tet for the indicated time. Viable cell numbers were determined by trypan blue staining (n = 3). Whole cell lysates were analyzed by immunoblotting with antibodies against ABL (BCR-ABL), phosphotyrosine (P-BCR-ABL), CHIP, c-Cbl, GFP, and actin. (B) p185 BCR-ABL–expressing Ba/F3 cells with the tet regulatory expression system for CHIP were deprived of tet for 14 hours. The cells were further incubated with cycloheximide (200μg/mL) together with or without GA (0.3μM) for indicated times. Whole cell lysates at each time point were analyzed by immunoblotting with antibodies against ABL, CHIP, and actin. (C) K562 cells were daily transfected with anti-CHIP and anti–c-Cbl siRNAs for 5 days. Twenty hours after the last transfection, the cells were incubated with or without GA (3μM) for 8 hours and analyzed by immunoblotting with antibodies against ABL, CHIP, and actin. The data were expressed as percentage of the signals obtained with each control. The bottom graph shows quantification of relative amounts of BCR-ABL proteins.