Project description:Genetic studies in T-cell acute lymphoblastic leukemia have uncovered a remarkable complexity of oncogenic and loss-of-function mutations. Amongst this plethora of genetic changes, NOTCH1 activating mutations stand out as the most frequently occurring genetic defect, identified in more than 50% of T-cell acute lymphoblastic leukemias, supporting an essential driver role for this gene in T-cell acute lymphoblastic leukemia oncogenesis. In this study, we aimed to establish a comprehensive compendium of the long non-coding RNA transcriptome under control of Notch signaling. For this purpose, we measured the transcriptional response of all protein coding genes and long non-coding RNAs upon pharmacological Notch inhibition in the human T-cell acute lymphoblastic leukemia cell line CUTLL1 using RNA-sequencing. Similar Notch dependent profiles were established for normal human CD34+ thymic T-cell progenitors exposed to Notch signaling activity in vivo. In addition, we generated long non-coding RNA expression profiles (array data) from GSI treated T-ALL cell lines, ex vivo isolated Notch active CD34+ and Notch inactive CD4+CD8+ thymocytes and from a primary cohort of 15 T-cell acute lymphoblastic leukemia patients with known NOTCH1 mutation status. Integration of these expression datasets with publically available Notch1 ChIP-sequencing data resulted in the identification of long non-coding RNAs directly regulated by Notch activity in normal and malignant T-cell context. Given the central role of Notch in T-cell acute lymphoblastic leukemia oncogenesis, these data pave the way towards development of novel therapeutic strategies that target hyperactive Notch1 signaling in human T-cell acute lymphoblastic leukemia. Gene expression was measured in the CUTLL1 T-ALL cell line after treatment with GSI or DMSO (solvent control). Cells were collected 12h and 48h after treatment. This was performed for 3 replicates.
Project description:T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic cancer frequently associated with activating mutations in NOTCH1. Early studies identified NOTCH1 as an attractive therapeutic target for the treatment of T-ALL through the use of gamma-secretase inhibitors (GSIs). Here, we characterized the interaction between PF-03084014, a clinically-relevant GSI, and dexamethasone in preclinical models of glucocorticoid-resistant T-ALL. Combination treatment of the GSI PF-03084014 with glucocorticoids induced a synergistic antileukemic effect in human T-ALL cell lines and primary human T-ALL patient samples. Molecular characterization of the response to PF-03084014 plus glucocorticoids through gene expression profiling revealed transcriptional upregulation of the glucocorticoid receptor as the mechanism mediating the enhanced glucocorticoid response. Moreover, treatment with PF-03084014 and glucocorticoids in combination was highly efficacious in vivo, with enhanced reduction of tumor burden in a xenograft model of T-ALL. Finally, glucocorticoid treatment was highly effective at reversing PF-03084014-induced gastrointestinal toxicity via inhibition of goblet cell metaplasia. These results suggest that combination of PF-03084014 treatment with glucocorticoids may be well-tolerated and highly active for the treatment of glucorticoid-resistant T-ALL. Duplicate samples of the CUTLL1 T-ALL cell line were treated with vehicle only (DMSO), the gamma-secretase inhibitor PF-03084014 (1 microM), dexamethasone (1 microM), or PF-03084014 (1 microM). plus dexamethasone (1 microM) for 48 hours. Gene expression profiling was analyzed to identify gene expression signatures assocuated with glucocorticoid treatment (dexamethasone), inhibition of NOTCH1 by gamma secretase inhibitor (PF-03084014) or the combination of both treatments.