Figure 4. BCL-2 mediates IL-7–induced DEX resistance.

(A) Percentage of priming of CCRF-CEM cells treated in the absence or presence of 1 μM DEX and/or 100 ng/mL IL-7 in technical triplicate for 16 hours followed by BH3 profiling with 0.5 μM ABT-199 for 90 minutes. (B) Viability of CCRF-CEM cells treated with DEX in the absence or presence of 25 ng/mL IL-7 and increasing concentrations of ABT-199 for 72 hours in technical triplicate. The no IL-7 (black line) and the 25 ng/mL IL-7 (red line) conditions were replotted from Figure 1C. (C) Heatmap of Bliss independence scores calculated as the average of technical triplicates for the combination of DEX and ABT-199 in the presence of 25 ng/mL IL-7. (D) MFI of BCL-2 protein expression assessed in technical triplicate in untransduced CCRF-CEM cells and CCRF-CEM cells transduced with a nontargeting shRNA control (shControl) or a BCL2-targeting shRNA (shBCL2-1-5). Statistical significance is relative to the untransduced cells. (E) Viability of untransduced or shRNA-transduced CCRF-CEM cells treated with DEX in the absence or presence of 25 ng/mL IL-7 in technical triplicate for 72 hours. (F) FPKM values for BCL2 transcript levels according to published RNA-Seq data from diagnostic samples from patients enrolled in the COG AALL0434 trial, stratified on the basis of day-29 bone marrow MRD. (G) Schematic of the proposed model for the mechanism by which DEX paradoxically induces steroid resistance in T-ALL cells in the presence of IL-7. In the presence of DEX (right), the GR induces an increase in IL-7R expression (i), leading to an increase in IL-7R at the cell surface (ii). This in turn leads to an increase in STAT5 transcriptional activity (iii) that ultimately results in the upregulation of BCL-2 (iv). GRE, glucocorticoid response element. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 1-way ANOVA with Tukey’s method for multiple comparisons adjustment (A, D, and F). All CCRF-CEM cell data are representative of 3 independent experiments.