Notch1-induced Leukemia Research Articles

A Tumor Suppressor Enhancer of PTEN in T-cell development and leukemia.

Long-range oncogenic enhancers play an important role in cancer. Yet, whether similar regulation of tumor suppressor genes is relevant remains unclear. Loss of expression of PTEN is associated with the pathogenesis of various cancers, including T-cell leukemia (T-ALL). Here, we identify a highly conserved distal enhancer (PE) that interacts with the PTEN promoter in multiple hematopoietic populations, including T-cells, and acts as a hub of relevant transcription factors in T-ALL. Consistently, loss of PE leads to reduced PTEN levels in T-ALL cells. Moreover, PE-null mice show reduced Pten levels in thymocytes and accelerated development of NOTCH1-induced T-ALL. Furthermore, secondary loss of PE in established leukemias leads to accelerated progression and a gene expression signature driven by Pten loss. Finally, we uncovered recurrent deletions encompassing PE in T-ALL, which are associated with decreased PTEN levels. Altogether, our results identify PE as the first long-range tumor suppressor enhancer directly implicated in cancer.

Abstract B134: IMPDH1 and IMPDH2 as therapeutic targets in acute lymphoblastic leukemia

Abstract Acute lymphoblastic leukemia (ALL) tumors are dependent on purine biosynthesis for proliferation and survival and relapsed ALL is particularly associated with transcriptional up-regulation of this pathway. Increased dependency on purine biosynthesis highlights IMPDH (inosine monophosphate dehydrogenase), the rate-limiting enzyme in guanosine production, as a potential therapeutic target for the treatment of ALL. To assess the role of IMPDH1 and IMPDH2 in ALL development and progression, we generated NOTCH1-induced leukemias from Impdh1 knockout and Impdh2 conditional knockout mice. In addition, we have completed whole exome sequencing and RNAseq profiling of 12 pairs of ALL xenografts corresponding to matched diagnostic and relapsed ALL samples and have performed dose response assays with the IMPDH inhibitor mizoribine. Additionally and towards the identification of synthetic lethal genetic vulnerabilities with IMPDH inhibition in ALL we have performed a genome wide CRISPR screen in REH ALL cells with the IMPDH inhibitor mizoribine. Overall, these studies highlight the therapeutic potential for IMPDH inhibitors for the treatment of ALL. Citation Format: Chelsea Dieck, Koichi Oshima, Alberto Ambesi-Impiombato, Adolfo Ferrando. IMPDH1 and IMPDH2 as therapeutic targets in acute lymphoblastic leukemia [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B134. doi:10.1158/1535-7163.TARG-19-B134

Abstract IA22: An oncogenic enhancer drives NOTCH1-induced leukemia.

Abstract Most genetic abnormalities found in cancer are located in intergenic regions and their role in cancer development remains poorly understood. Here we report the identification of a long range enhancer driving NOTCH1-induced transformation in T-ALL. Using genome wide ChIPseq mapping of NOTCH1 binding and functional epigenetic marks in T-ALL we identified a NOTCH1-occupied enhancer located in a gene desert island in 8q24, +1,427 kb 3' from the MYC locus. This regulatory element named N-Me for NOTCH-bound MYC enhancer activates MYC reporter constructs in T-ALL cells and directly interacts with MYC promoter sequences via long range chromatin loops. Notably, high resolution aCGH analysis revealed recurrent focal duplications at chromosome 8q24 encompassing this enhancer in 8/160 (5%) T-ALL cases. Functional characterization of N-Me in T-cell development and transformation using N-Me knockout and conditional knockout mice revealed a major role for this enhancer during thymocyte development and in T-ALL. Thus N-Me null animals showed a marked and selective reduction in thymus size and cellularity and were completely resistant to NOTCH1-induced transformation. Moreover, secondary deletion of N-Me in established NOTCH1 induced leukemias from tamoxifen-inducible N-Me conditional knockout mice induced profound antileukemic effects with extended survival and almost complete suppression of leukemia initiating cell activity. Altogether, these results identify N-Me as a major downstream effector NOTCH1 critically required for MYC expression in T-cell development and leukemia. Citation Format: Adolfo Ferrando. An oncogenic enhancer drives NOTCH1-induced leukemia. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr IA22.

Therapeutic targeting of HES1 transcriptional programs in T-ALL

AbstractOncogenic activation of NOTCH1 signaling plays a central role in the pathogenesis of T-cell acute lymphoblastic leukemia, with mutations on this signaling pathway affecting more than 60% of patients at diagnosis. However, the transcriptional regulatory circuitries driving T-cell transformation downstream of NOTCH1 remain incompletely understood. Here we identify Hairy and Enhancer of Split 1 (HES1), a transcriptional repressor controlled by NOTCH1, as a critical mediator of NOTCH1-induced leukemogenesis strictly required for tumor cell survival. Mechanistically, we demonstrate that HES1 directly downregulates the expression of BBC3, the gene encoding the PUMA BH3-only proapoptotic factor in T-cell acute lymphoblastic leukemia. Finally, we identify perhexiline, a small-molecule inhibitor of mitochondrial carnitine palmitoyltransferase-1, as a HES1-signature antagonist drug with robust antileukemic activity against NOTCH1-induced leukemias in vitro and in vivo.

Abstract 965: An oncogenic metabolic switch mediates resistance to NOTCH1 inhibition in T-ALL

Abstract Activating mutations of NOTCH1 are common in T-cell acute lymphoblastic leukemia (T-ALL), making NOTCH signaling a promising target for drugs such as γ-secretase inhibitors (GSIs), which block a proteolytic cleavage required for NOTCH activation. Aberrant activation of the PI3K-AKT pathway due to mutational loss of PTEN is found in 20% of human T-ALLs and has been linked with in vitro resistance to GSIs. Still, the specific mechanisms driving the antileukemic effects of NOTCH inhibition and the role of PTEN loss in resistance to anti-NOTCH therapies in T-ALL remain poorly understood. Here we used a mouse model of NOTCH1-induced leukemia built into conditional-inducible Pten knockout mice to demonstrate that genetic loss of Pten results in GSI resistance, accelerated mortality and progression under therapy in vivo. Importantly, gene expression profiling of tumor cells upon NOTCH inhibition showed that while NOTCH direct target genes are downregulated in both Pten-positive and Pten-deleted tumors, Pten loss results in global reversal of much of the transcriptional effects of NOTCH inhibition. Thus, Pten loss rescued the downregulation of genes involved in anabolic pathways and the upregulation of genes involved in catabolic pathways and autophagy induced by GSI treatment in Pten wild type leukemias. Consistently, electron microscopy and LC3 analysis demonstrated increased autophagy in NOTCH1 induced tumors upon GSI treatment, which was reversed upon Pten deletion. Moreover, global metabolomics analyses demonstrated that NOTCH inactivation induces a global anabolic shutdown in T-ALL with a marked block of glycolysis and glutaminolysis in Pten wild type tumor cells. Of note, flux studies using 13C-labeled glucose and 13C-labeled glutamine pointed to decreased metabolism with a specific block in glutaminolysis as critical effectors of the antileukemic effects of GSIs in T-ALL. Notably, each of the metabolic effects associated with NOTCH inhibition was effectively reversed upon genetic loss of Pten, supporting that metabolic rescue induced by Pten loss may mediate resistance to GSI therapy. Consistently, treatment with methyl pyruvate, a membrane soluble metabolite, effectively rescued the antileukemic effects of NOTCH inhibition, while, inhibition of glutaminolysis with a glutaminase inhibitor (BPTES) strongly and synergistically enhanced the antileukemic effects of NOTCH inhibition in T-ALL. Overall, these results formally demonstrate that loss of PTEN induces in vivo resistance to NOTCH inhibition in T-ALL; highlight the fundamental role of NOTCH1 in the control of tumor cell metabolism; implicates sustained carbon metabolism induced by Pten loss as mechanism of resistance to GSI therapy; and provide the framework for the development of novel therapies targeting glutaminolysis and cell metabolism in T-ALL. Citation Format: Daniel Herranz, Alberto Ambesi-Impiombato1, Jessica Sudderth, Marta Sánchez-Martín, Valeria Tosello, Luyao Xu, Mireia Castillo, Carlos Cordon-Cardo, Andrew L. Kung, Ralph J. DeBerardinis, Adolfo Ferrando. An oncogenic metabolic switch mediates resistance to NOTCH1 inhibition in T-ALL. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 965. doi:10.1158/1538-7445.AM2014-965

Abstract 4433: Fbxw11 promotes leukemia development by activating the NF-κB signaling pathway

Abstract F-box proteins serve as the substrate recognition subunit for the SCF E3 ubiquitin ligases. These ligases ubiquitinate specifically phosphorylated substrates and play a pivotal role in the regulation of various signal transduction pathways, which, in turn, are essential for many aspects of tumorigenesis. However the role of Fbxw11 in the development of leukemia and the underlying mechanisms remain largely unknown. Here, we found two transcript variants (Fbxw11c and Fbxw11d) expressed in mouse bone marrow. More importantly, the expression of Fbxw11 in normal hematopoietic stem cells (HSCs) from Notch1-induced leukemia mice was higher than that from control mice. In order to investigate the role of Fbxw11 in leukemia, we established L1210 cell lines over-expressing Fbxw11c or Fbxw11d respectively using the lentivirus system. Over-expression of both Fbxw11 variants stimulated the proliferation of L1210 cells in vitro by cell counting and MTT assay. The tumor xenografts model with over-expression of Fbxw11c or Fbxw11d in DBA/2 mice was further established. Over-expression of both variants resulted in the increased tumor growth in vivo. Investigation of the molecular mechanism revealed that the increased cell proliferation was not due to decrease in cell apoptosis but due to increase in cell cycle. Further studies showed that overexpression of both Fbxw11c and Fbxw11d caused the activation of NF-κB signaling pathway. These findings suggest the important role of Fbxw11 in regulating the development of leukemia and indicate a potent rationale for developing Fbxw11 as a potential therapeutic target against leukemia. Citation Format: Lina Wang, Jinfeng Liao, Xiao Yang, Wenli Feng, Shayan Chen, Guoguang Zheng. Fbxw11 promotes leukemia development by activating the NF-κB signaling pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4433. doi:10.1158/1538-7445.AM2014-4433

Kinetics of normal hematopoietic stem and progenitor cells in a Notch1-induced leukemia model

AbstractThe predominant outgrowth of malignant cells over their normal counterparts in a given tissue is a shared feature for all types of cancer. However, the impact of a cancer environment on normal tissue stem and progenitor cells has not been thoroughly investigated. We began to address this important issue by studying the kinetics and functions of hematopoietic stem and progenitor cells in mice with Notch1-induced leukemia. Although hematopoiesis was progressively suppressed during leukemia development, the leukemic environment imposed distinct effects on hematopoietic stem and progenitor cells, thereby resulting in different outcomes. The normal hematopoietic stem cells in leukemic mice were kept in a more quiescent state but remained highly functional on transplantation to nonleukemic recipients. In contrast, the normal hematopoietic progenitor cells in leukemic mice demonstrated accelerated proliferation and exhaustion. Subsequent analyses on multiple cell-cycle parameters and known regulators (such as p21, p27, and p18) further support this paradigm. Therefore, our current study provides definitive evidence and plausible underlying mechanisms for hematopoietic disruption but reversible inhibition of normal hematopoietic stem cells in a leukemic environment. It may also have important implications for cancer prevention and treatment in general.

NOTCH1-induced T-cell leukemia in transgenic zebrafish

Activating mutations in the NOTCH1 gene have been found in about 60% of patients with T-cell acute lymphoblastic leukemia (T-ALL). In order to study the molecular mechanisms by which altered Notch signaling induces leukemia, a zebrafish model of human NOTCH1-induced T-cell leukemia was generated. Seven of sixteen mosaic fish developed a T-cell lymphoproliferative disease at about 5 months. These neoplastic cells extensively invaded tissues throughout the fish and caused an aggressive and lethal leukemia when transplanted into irradiated recipient fish. However, stable transgenic fish exhibited a longer latency for leukemia onset. When the stable transgenic line was crossed with another line overexpressing the zebrafish bcl2 gene, the leukemia onset was dramatically accelerated, indicating synergy between the Notch pathway and the bcl2-mediated antiapoptotic pathway. Reverse transcription-polymerase chain reaction analysis showed that Notch target genes such as her6 and her9 were highly expressed in NOTCH1-induced leukemias. The ability of this model to detect a strong interaction between NOTCH1 and bcl2 suggests that genetic modifier screens have a high likelihood of revealing other genes that can cooperate with NOTCH1 to induce T-ALL.