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Sam68-mediated disruption of CBP/β-catenin neoplastic transcriptional programming allows selective targeting of human cancer stem cells

ABSTRACT: Increasing evidence suggests that cancer arises from cells that are capable of initiating and sustaining neoplastic tissue growth, termed cancer stem cells (CSCs). Of central scientific and clinical relevance, cells with CSC properties are enriched for chemo- and radiation resistance and therefore may represent a population of cells that must be therapeutically targeted to prevent cancer recurrence/relapse 1. Human CSCs were first isolated in neoplastic hematopoietic tissue that manifests leukemias such as adult acute myeloid leukemia (AML) 2. AML stem cells represent a benchmark model of human CSC biology, ultimately motivating foundational studies leading to the identification of CSCs from solid tumours such as breast and colon 3. Independent of tissue type, a consistent feature of CSCs is their uncontrolled self-renewal capacity and differentiation blockade that have been commonly related to aberrant activation of pro-oncogenic events such as dysregulation of CBP/p300 transcriptional regulation involving β-catenin 4. However, the transcriptional networks involving CBP/p300/β-catenin complex have been shown to be equally critical to maintain normal stem cell (SCs) self-renewal for tissue homeostasis and regeneration 5. Here, we identify Sam68 as a distinct target that affords the ability to uniquely regulate CBP mediated transcription in human CSCs. Using a small molecule that targets Sam68, we reveal that shifting its affinity for CBP disrupts CBP/β-catenin complexes, leading to immediate changes in histone H3 (K14 and K18) acetylation. Chemical targeting of Sam68 induced global changes in transcriptional programs of patient AML cells involving apoptosis and differentiation and was able to uniquely reduce neoplastic self-renewal of human CSCs in an in vivo model of patient specific acute myeloid leukemia (AML). Our study establishes an approach whereby the CBP/β-catenin transcriptome can be uniquely targeted via Sam68 based vulnerability of CSCs that impacts neoplastic differentiation and self-renewal.

ORGANISM(S): Homo sapiens

PROVIDER: GSE34965 | GEO | 2017/10/10

SECONDARY ACCESSION(S): PRJNA156131

REPOSITORIES: GEO

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Project description:The cellular origin and molecular progression towards aggressive cancers such as acute myeloid leukemia (AML) remain elusive. Clinically, Myelodysplastic syndromes (MDS) and related myeloproliferative neoplasias (MPN) disorders1-5 are believed to present as a precursor stage to lethal AML development. Despite the identification of cytogenetic abnormalities and increased activation of signaling in human MDS/MPN, specific pathways that either sustain or initiate disease progression and evolve into self-sustaining leukemic-initiating cells (L-ICs)13 have not been elucidated. Here we demonstrate that tissue specific loss of glycogen synthase kinase-3Î² (GSK3 betaÎ²) initiates the emergence of stable Pre-leukemic-ICs (PLIC) in vivo. In contrast to deletion or transgenic perturbation of pathways associated with AML eg. Î²-catenin/Wnt, serial transplantation of PL-IC produced abnormal hematological disease that phenotypically and molecularly resembles human MDS/MPN. PL-ICs were exclusively generated from GSK3 betaÎ² deficient hematopoietic stem cells (HSCs), indicating that disease initiation events collaborate with existing HSC self-renewal machinery. In the absence of GSK3 betaÎ², subsequent deletion of GSK3 betaÎ± caused rapid induction of L-ICs that give rise to lethal AML. As these processes were solely driven by dose-dependent deficiencies in GSK3 beta levels, our results suggest that perturbation of this pathway can sufficiently drive and recapitulate a step-wise progression of disease from HSCs to MDS/MPN and subsequent AML. Our study provides a molecular and cellular foundation to understand AML evolution from pre-leukemic precursors. We suggest that defining the molecular states of pre-neoplastic disease will allow patient stratification at early stages of MDS/MPN onset and aid in the development of therapeutic targeting of causal pathways responsible for the earliest stages of leukemic initiation events. 5 week post-transplanted recipient mice (CD45.1) with either Lin- bone marrow GSK3 alpha +/+ beta +/flx, alpha+/+ beta flx/flx, alpha -/- beta +/+ or alpha-/- beta fx/flx Rosa26-CreERTM cells (CD45.2) were induced 3 times with intraperitoneal injections of Tamoxifen (75mg/kg) at intervals of two to three days. Mice were sacrificed and analyzed 4 weeks after injection. Bone marrow lineage negative (Lin-), Sca1+, cKit+ cells were sorted from engrafted Lin- bone marrow GSK3 alpha +/+ beta +/flx, alpha+/+ beta flx/flx, alpha -/- beta +/+ or alpha-/- beta fx/flx cells for RNA extraction. Total RNA from purified populations was extracted and amplified as described previously (Shojaei et al., 2005). Amplified-labeled RNA was hybridized to Affymetrix Mouse Genome 430 2.0 Array.

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Sam68-mediated disruption of CBP/β-catenin neoplastic transcriptional programming allows selective targeting of human cancer stem cells

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