Abstract 2438: Genome-wide screen reveals a role for glucocorticoids in B cell development that can be exploited to improve treatment of B cell acute lymphoblastic leukemia

Abstract

Abstract Glucocorticoids (GCs) are a component of highly effective therapy for B cell acute lymphoblastic leukemia (B-ALL), the most common childhood cancer. Although successful in 90% of patients, the prognosis for the remaining 10% is dismal. Because sensitivity to GCs alone predicts outcome well, we hypothesized that enhancing or restoring GC sensitivity can improve outcome. To first determine how GCs kill B-ALL cells, we first measured the transcriptional response of sensitive B-ALL samples to dexamethasone (dex). In addition to apoptotic genes (BIM, BCL2), and metabolic genes (TXNIP) identified in other studies that contribute to cell death, we also found broad regulation of B cell development genes, including key checkpoints (ITGA4, IL7R, and BCL6). This suggested that high levels of GCs push arrested B-ALL cells through development, resulting in cell death. To validate these results, and to identify cellular pathways that modulate GC cytotoxicity, we used a next-generation shRNA screen to knock down every protein-coding gene in the genome. The screen identified 265 genes that significantly modulate GC sensitivity. In addition to validating the importance lymphoid development genes, the screen revealed which cofactors and chromatin modifiers collaborate with GR to orchestrate cell death gene programs. Further we were able to map critical signaling pathways with high resolution, including the pro-survival B cell receptor pathway. Inhibition of PI3Kδ at the apex of this pathway potentiated the response of GC-regulated genes to dex, and synnergized with dex to induce cell death in even the most refractory B-ALL tissue. These results indicate a previously unrecognized for GCs in B cell development that can be exploited to improve both the potency and treatment of lymhoid disease. Citation Format: Miles Pufall, Karina Kruth, Sarah K. Tasian. Genome-wide screen reveals a role for glucocorticoids in B cell development that can be exploited to improve treatment of B cell acute lymphoblastic leukemia. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2438.