Enforcement of stem-cell dormancy by NPMc+ is a critical determinant of unrestricted self-renewal during myeloid leukemogenesis
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ABSTRACT: Purpose: Analysis of downstream pathways activated by NPMc+ and Flt3-ITD oncogenes in preleukemic hematopoietic stem cells (HSCs). Methods: RNA extracted and processed from MxCRE, Flt3-ITD and NPMc+/Flt3-ITD FACS sorted HSCs Results: These data demonstrate that NPMc+ expression in Flt3-ITD HSCs promote a transcriptional program that supports both self-renewal and quiescence.
Project description:Analysis of the transcriptional profile imposed by NPMc+ and Flt3-ITD oncogenes, both alone and in cooperation, on HSCs at single cell level
Project description:The most frequent mutation in AML patients with normal karyotype affects the Nucleophosmin gene (NPMc+). Different mouse models have shown that NPMc+ mutation can drive leukemia development. In this study, the impact of NPMc+ expression on the transcriptional program of mouse hematopietic stem cells (HSC) in vivo has been investigated.
Project description:Acute myeloid leukemia (AML) carrying NPM1 mutations and cytoplasmic nucleophosmin (NPMc+ AML) accounts for about one-third of adult AML and shows distinct features, including a unique gene expression profile. MicroRNAs (miRNAs) are small noncoding RNAs of 19-25 nucleotides in length that have been linked to the development of cancer. Here, we investigated the role of miRNAs in the biology of NPMc+ AML. The miRNA expression was evaluated in 85 adult de novo AML patients characterized for subcellular localization/mutation status of NPM1 and FLT3 mutations using a custom microarray platform. Data were analyzed by using univariate t test within BRB tools. We identified a strong miRNA signature that distinguishes NPMc+ mutated (n = 55) from the cytoplasmic-negative (NPM1 unmutated) cases (n = 30) and includes the up-regulation of miR-10a, miR-10b, several let-7 and miR-29 family members. Many of the down-regulated miRNAs including miR-204 and miR-128a are predicted to target several HOX genes. Indeed, we confirmed that miR-204 targets HOXA10 and MEIS1, suggesting that the HOX up-regulation observed in NPMc+ AML may be due in part by loss of HOX regulators-miRNAs. FLT3-ITD+ samples were characterized by up-regulation of miR-155. Further experiments demonstrated that the up-regulation of miR-155 was independent from FLT3 signaling. Our results identify a unique miRNA signature associated with NPMc+ AML and provide evidence that support a role for miRNAs in the regulation of HOX genes in this leukemia subtype. Moreover, we found that miR-155 was strongly but independently associated with FLT3-ITD mutations.
Project description:Transcriptional profiling of murine cells expressing PML/RARA at the early promyelocyte stage (4 weeks old, preleukemic) and in full blown PML/RARA leukemia generated by transducing PML/RARA bone marrow with a Flt3-ITD retroviral vector Two-conditions experiment: preleukemic early promyelocytes vs leukemic promyelocytes
Project description:Examination of gene expression patterns in lineage negative FLT3-ITDâ and pMIG-transduced BM cells via microarray study. We performed a global mRNA profiling analysis of murine Linâ FLT3-ITD+ cells compared to empty-vector controls, purified 48h after transduction. We examined association patterns of FLT3-ITD and pMIG cells and identified a specific gene expression signature associated with FLT3-ITD signalling. Total RNA obtained from isolated lineage negative BM cells subjected to 48h of FLT3-ITD signalling compared to empty vector control.
Project description:Examination of gene expression patterns in lineage negative FLT3-ITD– and pMIG-transduced BM cells via microarray study. We performed a global mRNA profiling analysis of murine Lin– FLT3-ITD+ cells compared to empty-vector controls, purified 48h after transduction. We examined association patterns of FLT3-ITD and pMIG cells and identified a specific gene expression signature associated with FLT3-ITD signalling.
Project description:Leukemic stem cells (LSCs) fuel relapse in acute myeloid leukemia (AML), but therapies tailored at eradicating LSCs without harming healthy hematopoietic stem cells (HSCs) are lacking. FLT3 is frequently mutated in AML and associated with relapse; but FLT3 targeting has met with limited clinical success. This raises questions of whether more potent inhibitors would increase effectiveness but whether toxicity to HSC would become limiting. Here, we tested the consequence of complete FLT3 ablation using CRISPR/Cas9 FLT3 knock-out (FLT3-KO) in human HSCs and LSCs followed by functional xenograft assays to test their ability to regenerate human hematopoiesis and leukemia, respectively. FLT3-KO in HSCs from human fetal liver, cord blood and adult bone marrow showed no impairment in multilineage hematopoiesis in primary and secondary xenografts. By contrast, FLT3-KO LSCs from 6 of 7 FLT3-ITD mutated AMLs were able to generate short-term engraftment but were completely exhausted by 12 weeks. Thus, FLT3 is essential for LSC long-term propagation. This dependency was unique to FLT3-ITD AML samples as non-FLT3-ITD AML samples generated leukemic grafts upon FLT3-KO. Transcriptomic analysis revealed that FLT3-KO induced downregulation of DNA repair and cell cycle checkpoints, uniquely in FLT3-ITD AML, but not in healthy HSCs or other AMLs. Our research highlights a critical distinction between healthy HSCs and LSCs: whereas healthy hematopoiesis proceeds unperturbed upon FLT3-KO, FLT3-ITD leukemogenesis is impaired through elimination of LSCs. This evidence underscores the necessity for more potent FLT3-targeting and places FLT3 as an ideal therapeutic target to selectively eradicate LSCs, while sparing HSC.
Project description:Transcriptional profiling of murine cells expressing PML/RARA at the early promyelocyte stage (4 weeks old, preleukemic) and in full blown PML/RARA leukemia generated by transducing PML/RARA bone marrow with a Flt3-ITD retroviral vector