Project description:The Notch signaling pathway regulates several processes including development and differentiation and its aberrant regulation leads to several diseases. Here, we analyzed the gene expression profile upon washout of the Notch inhibitor DAPT in mouse pre-T (Beko) cells.
Project description:The Notch signaling pathway regulates several differentiation and developmental processes in both pre- and post-natal life and its aberrant regulation leads to diseases, including cancer. Here, we investigated the role of histone deacetylase 3 (HDAC3) on the regulation of the Notch-dependent gene expression program in mouse pre-T (Beko) cells. We first defined Notch target genes as those genes that are downregulated upon inhibition of the Notch pathway using DAPT, a gamma-secretase inhibitor (GSI). Subsequently, we investigated the role of HDAC3 in the regulation of Notch target genes by shRNA- and pharmacologically (apicidin)-mediated loss-of-function of HDAC3.
Project description:The Notch signaling pathway regulates several processes including development and differentiation and its aberrant regulation leads to several diseases. Here, we investigated the differential chromatin accessibility, genome-wide distribution of the transcription factor RBPJ and the differential regulation of H3K4me1 and H3K4me3 upon pharmacological inhibition of the Notch pathway with gamma-secretase inibibitor (GSI) DAPT in mouse pre-T (Beko) cells.
Project description:The Notch signaling pathway regulates several processes including development and differentiation and its aberrant regulation leads to several diseases. Here, we investigated the differential chromatin accessibility, genome-wide distribution of the transcription factor RBPJ and the differential regulation of H3K4me1 and H3K4me3 upon pharmacological inhibition of the Notch pathway with gamma-secretase inibibitor (GSI) DAPT in mouse pre-T (Beko) cells.
Project description:The Notch signaling pathway regulates several processes including development and differentiation and its aberrant regulation leads to several diseases. Here, we investigated the differential chromatin accessibility, genome-wide distribution of the transcription factor RBPJ and the differential regulation of H3K4me1 and H3K4me3 upon pharmacological inhibition of the Notch pathway with gamma-secretase inibibitor (GSI) DAPT in mouse pre-T (Beko) cells.
Project description:NOTCH1 is a crucial oncogenic driver in T-cell acute lymphoblastic leukemia (T-ALL), making it an attractive therapeutic target. However, the success of targeted therapy using γ-secretase inhibitors (GSIs), small molecules blocking Notch cleavage and subsequent activation, has been limited due to toxicity and development of resistance, thus restricting their clinical efficacy. Here we systematically compare GSI resistant and sensitive cell states by quantitative mass spectrometry-based phosphoproteomics, using complementary models of resistance, including T-ALL patient-derived xenografts (PDX) models. Our datasets reveal common mechanisms of GSI resistance, including a distinct kinase signature that involves protein kinase C delta (PKCδ). We demonstrate that the PKC inhibitor sotrastaurin enhances the anti-leukemic activity of GSI in PDX models and completely abrogates the development of acquired GSI resistance “in-vitro”. Overall, we highlight the potential of proteomics to dissect alterations in cellular signaling and identify druggable pathways in cancer.
Project description:The NOTCH signaling cascade, which is deregulated in T-cell acute lymphoblastic leukemia (T-ALL) and many other human cancers, offers an attractive target for molecular therapy. One approach employs gamma-secretase inhibitors (GSIs) to suppress production of the intracellular form of NOTCH (NICD), leading to cell growth arrest and apoptosis. Here we show that missense mutations or homozygous deletion of FBW7, which encodes a ubiquitin ligase that targets the NICD for destruction, mediate constitutive NICD expression. FBW7 mutations target key arginine residues needed for binding to the NICD. Although the mutant forms of Fbw7 still bind to MYC, they do not target MYC for degradation, suggesting that stabilization of both NICD and MYC may contribute to transformation in leukemias with mutations in FBW7. Leukemias with FBW7 mutations are resistant to the growth suppressive and apoptotic effects of the MRK-003 GSI. In some resistant lines that express the NICD, this resistance is accompanied by sustained mRNA levels of the NOTCH target DELTEX1 as well as MYC mRNA and protein, implying that residual NICD activity due to the mutant FBW7 can contribute to GSI resistance. Keywords: T-ALL, gamma-secretase, GSI, cell line comparison, FBW7 mutation
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. CUTLL1 cell lines were treated with Compound E (GSI) or DMSO (solvent control). Cells were collected 12 h and 48 h after treatment. This was performed for 3 replicates. RNA-sequencing was performed on these samples.
Project description:Notch is normally activated by cleavage and nuclear translocation of its intracellular domain (ICN1), which turns on downstream target genes. Human T cell acute lymphoblastic leukemia (T-ALL), an aggressive immature T cell malignancy, is associated with Notch 1 gain-of-function mutations in more than 50% of the cases. Efforts to date to identify direct Notch1 targets have been confounded by the lack of a method to turn Notch1 on in a controlled fashion in T-ALL cells that are poised to respond to Notch signals. Of note, because Notch signaling activates transcriptional repressors that feedback to dampen the expression of many target genes (a process referred to as incoherent logic), it is likely that many direct targets are missed in Notch off analyses, which are further complicated by an inability to identify direct targets in a clear-cut fashion. We have overcome this limitation by developing a GSI washout method that results in the rapid translocation of activated Notch1 to the nucleus. We intend to use this method to study the assembly and loading of transcriptional complexes onto downstream targets, the kinetics of target activation. To date, our efforts have been devoted to comparing the gene expression signature of Notch-on and Notch-off in the human T-ALL cell line CUTLL. In addition to previously identified Notch1 target genes, we have also identified a series of novel genes upregulated by GSI washout in the presence of cycloheximide, suggesting that they are likely to be direct targets. Additional controls included transduction of cells with dominant negative MAML1, a specific antagonist of canonical Notch1 signaling, prior to Notch1 reactivation, and a mock GSI washout to control for cycloheximide effects. CUTLL1 cells are cultured in triplicates with different treatments. Total RNA was prepared and hybridized to Affymetrix human U133 plus 2.0 microarrays