Time course of GR and Bim protein expression in CEM-WT and MTX-R3 cells and changes in GR expression and effects on cell viability in xenograft cells exposed to dexamethasone. (A) CEM-WT and MTX-R3 cells were exposed to dexamethasone (1 μM) and harvested at the indicated time points. Total cellular protein (75 μg) was separated by SDS-PAGE and immunoblotted for GR, actin, and Bim protein expression. Data shown are representative of 2 independent experiments. (B-D) Xenograft cells were retrieved from cryostorage and exposed to dexamethasone (1 μM), and whole cell lysates were prepared at appropriate time points thereafter (0, 8, 16, 20, 24, and 48 hours). (B) Total cellular protein (50 μg) was separated by SDS-PAGE and immunoblotted for GR and actin. C indicates solvent-treated controls. (C) Quantitative data showing GR down-regulation with respect to actin in all 4 xenografts. (D) Cell viability was assessed by trypan blue exclusion at each time point. □ represents ALL-3; ▴, ALL-7; ○, ALL-16; and , ALL-19. In panels C and D each data point represents the mean ± SEM of 3 independent experiments.