BTG1 expression is essential for the induction of GC-mediated cell death. (A) Quantitative RT-PCR analysis of BTG1 in total mRNA of primary pre-B and T-ALL and RS4;11 cell line after exposure to 1 mg/mL prednisolone dissolved in medium or medium alone for 8 hours. Expression values were normalized for TBP. Titration of the prednisolone concentration revealed that efficient induction of BTG1 mRNA, after 8-hour exposure to prednisolone, could be observed at concentrations as low as 5.0 × 10−1 μg/mL (supplemental Figure 3B). (B) Quantitative PCR analysis of BTG1mRNA in RS4;11 cell lines transduced with control or either of 2 independent shRNAs targeting different regions of the BTG1 gene (shRNA1 and shRNA2). Cells were exposed to 1 mg/mL prednisolone for up to 8 hours. (C) The relative increase in cell number of the RS4;11 control, BTG1 shRNA 1, and BTG1 shRNA 2 cell lines was determined during 4 days of culture. (D-E) Determination of relative viability of RS4;11 control, BTG1 shRNA 1, and BTG1 shRNA 2 cell lines as determined by an MTS-based cytotoxicity assay after 3 days of exposure to increasing concentrations of prednisolone (D) or dexamethasone (E). Relative survival is determined as relative compared with the medium control. Data are mean ± SEM of triplicate experiments. Statistical significance was tested with 2-sided Student t test. (A) *Significant change compared with control cells (P < .05). (B) *Significant change compared with mock-treated control cells (P < .05). (C-E) *Significant change in both shRNA 1 and 2 compared with control cells that had received similar treatment (P < .05).
