Nextgen functional genomics identifies B-cell development genes, pathways, and feedback loops that affect dexamethasone activity in B-ALL.
Suppression of the lymphoid-restricted PI3Kδ synergizes with dex in B-ALL by enhancing or restoring regulation of cell-death genes.
Glucocorticoids (GCs), including dexamethasone (dex), are a central component of combination chemotherapy for childhood B-cell precursor acute lymphoblastic leukemia (B-ALL). GCs work by activating the glucocorticoid receptor (GR), a ligand-induced transcription factor, which in turn regulates genes that induce leukemic cell death. Which GR-regulated genes are required for GC cytotoxicity, which pathways affect their regulation, and how resistance arises are not well understood. Here we systematically integrate the transcriptional response of B-ALL to GCs with a next-generation shRNA screen to identify GC-regulated "effector" genes that contribute to cell death as well as genes that affect the sensitivity of B-ALL cells to dex. This analysis reveals a pervasive role for GCs in suppression of B-cell development genes that is linked to therapeutic response. Inhibition of PI3Kδ, a lynchpin in the pre-B-cell receptor and IL7R signaling pathways critical to B-cell development, with CAL-101 (idelalisib), interrupts a double-negative feedback loop, enhancing GC-regulated transcription to synergistically kill even highly resistant B-ALL with diverse genetic backgrounds. This work not only identifies numerous opportunities for enhanced lymphoid-specific combination chemotherapies that have the potential to overcome treatment resistance, but is also a valuable resource for understanding GC biology and the mechanistic details of GR-regulated transcription.
- Submitted February 2, 2017.
- Accepted March 29, 2017.
- Copyright © 2017 American Society of Hematology
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