scholarly journals A New Entity of Acute Myeloid Leukemia Driven By Epigenetic and Somatic Dis-Regulation of Uncx, a Novel Homeobox Transcription Factor Gene

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1356-1356
Author(s):  
Giulia Daniele ◽  
Clelia Tiziana Storlazzi ◽  
Cristina Papayannidis ◽  
Ilaria Iacobucci ◽  
Angelo Lonoce ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Transcription Factor ◽  
Myeloid Leukemia ◽  
De Novo ◽  
Ectopic Expression ◽  
Response To Therapy ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract We describe a new AML entity, occurring in 30% of de novo acute myeloid leukemia, due to structural and epigenetic deregulation of the UNCX homeobox (HB) gene. By molecular approaches, we identified a M5 AML patient with a t(7;10)(p22;p14) translocation as the sole cytogenetic anomaly and showing ectopic expression of UNCX (7p22.3), which encode for a transcription factor involved in somitogenesis and neurogenesis. Since UNCX was never reported in association with cancer but only with common myeloid cell proliferation and regulation of cell differentiation, we decided to investigate its contribution to leukemogenesis. We observed UNCX ectopic expression in 32.3% (20/62) and in 8% (6/75) of acute myeloid leukemia (AML) patients and cell lines, respectively. Notably, retroviral-mediated UNCX transfer in CD34+ HSCs induced a slow-down in their proliferation and differentiation and transduced cells showed a lower growth rate but a higher percentage of CD34+ stem cells in liquid culture than controls. Additionally, UNCX infected cells displayed a decrease of MAP2K1 proliferation marker but increase of KLF4, HOXA10, and CCNA1, associated with impaired differentiation and pluripotency. Similarly, UNCX-positive patients revealed alteration of gene pathways involved in proliferation, cell cycle control and hematopoiesis. Since HB genes encode for transcription factors showing a crucial role in normal hematopoiesis and in leukemogenesis, we focused our attention on the role of altered UNCX expression level. Of note, its murine ortholog, (Uncx) was previously described as embedded within a low-methylated regions (≤ 10%) called "canyon" and dysregulated in murine hematopoietic stem cells (HSCs) as a consequence of altered methylation at canyons edges (borders) due to Dnmt3a inactivation. In our hands, UNCX activation was accompanied by methylation changes at both its canyon borders, clearly indicating an epigenetic regulation of this gene, although not induced by DNMT3A mutations. Clinical parameters and correlation with response to therapy will be presented. Taken together, our results indicate that more than 30% of de novo AML have a novel entity with a putative leukemogenic role of UNCX, whose activation may be ascribed to epigenetic regulators. Acknowledgments: MG, CP, GS, and AP(2) and this work was supported by ELN, AIL, AIRC, progetto Regione-Università 2010-12 (L. Bolondi), Fondazione del Monte di Bologna e Ravenna, FP7 NGS-PTL project. CTS, GD and AL are supported by Associazione Italiana Ricerca sul Cancro (AIRC) funding. Disclosures Nadarajah: MLL Munich Leukemia Laboratory: Employment. Martinelli:MSD: Consultancy; Novartis: Consultancy, Speakers Bureau; Ariad: Consultancy; BMS: Consultancy, Speakers Bureau; Pfizer: Consultancy; AMGEN: Consultancy; ROCHE: Consultancy.

scholarly journals Evidence for malignant transformation in acute myeloid leukemia at the level of early hematopoietic stem cells by cytogenetic analysis of CD34+ subpopulations

Blood ◽  
1995 ◽  
Vol 86 (8) ◽  
pp. 2906-2912 ◽  
Author(s):  
D Haase ◽  
M Feuring-Buske ◽  
S Konemann ◽  
C Fonatsch ◽  
C Troff ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Malignant Transformation ◽  
Cell Sorting ◽  
Myeloid Leukemia ◽  
De Novo ◽  
Leukemic Cells ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Acute myeloid leukemia (AML) is a heterogenous disease according to morphology, immunophenotype, and genetics. The retained capacity of differentiation is the basis for the phenotypic classification of the bulk population of leukemic blasts and the identification of distinct subpopulations. Within the hierarchy of hematopoietic development and differentiation it is still unknown at which stage the malignant transformation occurs. It was our aim to analyze the potential involvement of cells with the immunophenotype of pluripotent stem cells in the leukemic process by the use of cytogenetic and cell sorting techniques. Cytogenetic analyses of bone marrow aspirates were performed in 13 patients with AML (11 de novo and 2 secondary) and showed karyotype abnormalities in 10 cases [2q+, +4, 6p, t(6:9), 7, +8 in 1 patient each and inv(16) in 4 patients each]. Aliquots of the samples were fractionated by fluorescence-activated cell sorting of CD34+ cells. Two subpopulations, CD34+/CD38-(early hematopoietic stem cells) and CD34+/CD38+ (more mature progenitor cells), were screened for karyotype aberations as a marker for leukemic cells. Clonal abnormalities and evaluable metaphases were found in 8 highly purified CD34+/CD38-populations and in 9 of the CD34+/CD38-specimens, respectively. In the majority of cases (CD34+/CD38-, 6 of 8 informative samples; CD34+/CD38+, 5 of 9 informative samples), the highly purified CD34+ specimens also contained cytogenetically normal cells. Secondary, progression-associated chromosomal changes (+8, 12) were identified in the CD34+/CD38-cells of 2 patients. We conclude that clonal karyotypic abnormalities are frequently found in the stem cell-like (CD34+/CD38-) and more mature (CD34+/CD38+) populations of patients with AML, irrespective of the phenotype of the bulk population of leukemic blasts and of the primary or secondary character of the leukemia. Our data suggest that, in AML, malignant transformation as well as disease progression may occur at the level of CD34+/CD38-cells with multilineage potential.

scholarly journals Gpr44 Mediates the Selenium-Dependent Anti-Leukemic Effect in Acute Myeloid Leukemia

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 1835-1835
Author(s):  
Fenghua Qian ◽  
Fenghua Qian ◽  
Diwakar Tukaramrao ◽  
Jiayan Zhou ◽  
Nicole Palmiero ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Murine Model ◽  
Myeloid Leukemia ◽  
Hematopoietic Stem ◽  
Cell Counts ◽  
Pparγ Agonist ◽  
Acute Myeloid

Abstract Objectives The relapse of acute myeloid leukemia (AML) remains a significant concern due to persistent leukemia stem cells (LSCs) that are not targeted by existing therapies. LSCs show sensitivity to endogenous cyclopentenone prostaglandin J (CyPG) metabolites that are increased by dietary trace element selenium (Se), which is significantly decreased in AML patients. We investigated the anti-leukemic effect of Se supplementation in AML via mechanisms involving the activation of the membrane-bound G-protein coupled receptor 44 (Gpr44) and the intracellular receptor, peroxisome proliferator-activated receptor gamma (PPARγ), by endogenous CyPGs. Methods A murine model of AML generated by transplantation of hematopoietic stem cells (HSCs- WT or Gpr44−/−) expressing human MLL-AF9 fusion oncoprotein, in the following experiments: To investigate the effect of Se supplementation on the outcome of AML, donor mice were maintained on either Se-adequate (Se-A; 0.08–0.1 ppm Se) or Se-supplemented (Se-S; 0.4 ppm Se) diets. Complete cell counts in peripheral blood were analyzed by hemavet. LSCs in bone marrow and spleen were analyzed by flow cytometry. To determine the role of Gpr44 activation in AML, mice were treated with Gpr44 agonists, CyPGs. LSCs in bone marrow and spleen were analyzed. Mice transplanted with Gpr44−/- AML cells were compared with mice transplanted with wild type AML cells and the progression of the disease was followed as above. To determine the role of PPARγ activation in AML, PPARγ agonist (Rosiglitazone, 6 mg/kg, i.p, 14 d) and antagonist (GW9662, 1 mg/kg, i.p. once every other day, 7 injections) were applied to Se-S mice transplanted with Gpr44−/- AML cells and disease progression was followed. Results Se supplementation at supraphysiological levels alleviated the disease via the elimination of LSCs in a murine model of AML. CyPGs induced by Se supplementation mediate the apoptosis in LSCs via the activation of Gpr44 and PPARγ. Conclusions Endogenous CyPGs produced upon supplementation with Se at supraphysiological levels improved the outcome of AML by targeting LSCs to apoptosis via the activation of two receptors, Gpr44 and PPARg. Funding Sources NIH DK 07,7152; CA 175,576; CA 162,665. Office of Dietary Supplements, USDA Hatch funds PEN04605, Accession # 1,010,021 (KSP, RFP).

scholarly journals microRNA-29a induces aberrant self-renewal capacity in hematopoietic progenitors, biased myeloid development, and acute myeloid leukemia

2010 ◽  
Vol 207 (3) ◽  
pp. 475-489 ◽  
Author(s):  
Yoon-Chi Han ◽  
Christopher Y. Park ◽  
Govind Bhagat ◽  
Jinping Zhang ◽  
Yulei Wang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Ectopic Expression ◽  
Hematopoietic Progenitors ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Myeloid Development ◽  
Acute Myeloid ◽  
Myeloid Progenitors

The function of microRNAs (miRNAs) in hematopoietic stem cells (HSCs), committed progenitors, and leukemia stem cells (LSCs) is poorly understood. We show that miR-29a is highly expressed in HSC and down-regulated in hematopoietic progenitors. Ectopic expression of miR-29a in mouse HSC/progenitors results in acquisition of self-renewal capacity by myeloid progenitors, biased myeloid differentiation, and the development of a myeloproliferative disorder that progresses to acute myeloid leukemia (AML). miR-29a promotes progenitor proliferation by expediting G1 to S/G2 cell cycle transitions. miR-29a is overexpressed in human AML and, like human LSC, miR-29a-expressing myeloid progenitors serially transplant AML. Our data indicate that miR-29a regulates early hematopoiesis and suggest that miR-29a initiates AML by converting myeloid progenitors into self-renewing LSC.

MicroRNA-29a Is An Oncogene in Acute Myeloid Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 683-683
Author(s):  
Christopher Y. Park ◽  
Yoon-Chi Han ◽  
Govind Bhagat ◽  
Jian-Bing Fan ◽  
Irving L Weissman ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Mirna Expression ◽  
Myeloid Leukemia ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract microRNAs (miRNAs) are short, non-protein encoding RNAs that bind to the 3′UTR’s of target mRNAs and negatively regulate gene expression by facilitating mRNA degradation or translational inhibition. Aberrant miRNA expression is well-documented in both solid and hematopoietic malignancies, and a number of recent miRNA profiling studies have identified miRNAs associated with specific human acute myeloid leukemia (AML) cytogenetic groups as well as miRNAs that may prognosticate clinical outcomes in AML patients. Unfortunately, these studies do not directly address the functional role of miRNAs in AML. In fact, there is no direct functional evidence that miRNAs are required for AML development or maintenance. Herein, we report on our recent efforts to elucidate the role of miRNAs in AML stem cells. miRNA expression profiling of AML stem cells and their normal counterparts, hematopoietic stem cells (HSC) and committed progenitors, reveals that miR-29a is highly expressed in human hematopoietic stem cells (HSC) and human AML relative to normal committed progenitors. Ectopic expression of miR-29a in mouse HSC/progenitors is sufficient to induce a myeloproliferative disorder (MPD) that progresses to AML. During the MPD phase of the disease, miR-29a alters the composition of committed myeloid progenitors, significantly expedites cell cycle progression, and promotes proliferation of hematopoietic progenitors at the level of the multipotent progenitor (MPP). These changes are manifested pathologically by marked granulocytic and megakaryocytic hyperplasia with hepatosplenomegaly. Mice with miR-29a-induced MPD uniformly progress to an AML that contains a leukemia stem cell (LSC) population that can serially transplant disease with as few as 20 purified LSC. Gene expression analysis reveals multiple tumor suppressors and cell cycle regulators downregulated in miR-29a expressing cells compared to wild type. We have demonstrated that one of these genes, Hbp1, is a bona fide miR-29a target, but knockdown of Hbp1 in vivo does not recapitulate the miR-29a phenotype. These data indicate that additional genes are required for miR-29a’s leukemogenic activity. In summary, our data demonstrate that miR-29a regulates early events in normal hematopoiesis and promotes myeloid differentiation and expansion. Moreover, they establish that misexpression of a single miRNA is sufficient to drive leukemogenesis, suggesting that therapeutic targeting of miRNAs may be an effective means of treating myeloid leukemias.

Minimal Reduction of PU.1 Is Sufficient to Induce a Preleukemic State and Promote Development of Acute Myeloid Leukemia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 305-305
Author(s):  
Britta Will ◽  
Thomas O. Vogler ◽  
Swathi-rao Narayanagari ◽  
Boris Bartholdy ◽  
Tihomira I. Todorova ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Transcription Factor ◽  
Malignant Transformation ◽  
Myeloid Leukemia ◽  
Complete Loss ◽  
Hematopoietic Stem ◽  
Minimal Reduction ◽  
Acute Myeloid

Abstract Genomic studies have shown that human cancer is rarely associated with a complete loss of transcripts; instead, acquired DNA alterations often occur within the non-coding part of the genome, are enriched in gene-regulatory regions, and cause only moderate transcriptional changes. It is currently not well understood how such moderate gene expression changes impact normal tissue function and how they contribute to malignant transformation. Acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) develop through a multi-step transformation process originating in hematopoietic stem cells (HSCs) and mainly present in the elderly (median age of >65 years at diagnosis). Although loss or near-complete loss of the hematopoietic transcription factor PU.1 induces AML in mice, a similar degree of PU.1 impairment is exceedingly rare in human AML; yet moderate PU.1 inhibition is common in AML patients. At the example of the Ets-family transcription factor PU.1, which is indispensable for HSC function and the differentiation of cells within the myeloid as well as lymphoid lineages, we tested the hypothesis that even moderate gene expression alterations of key regulators can drive malignant transformation. We assessed the effects of minimal PU.1 inhibition on hematopoiesis in a novel mouse model that co-models the genomic context found in aging human individuals and patients with MDS/AML. Mice lacking Msh2, the key component of the MutSα and MutSβ complexes mediating DNA mismatch repair, accumulate elevated numbers of point mutations, in particular C/G>T/A transitions and small insertions/deletions resembling the mutation spectrum acquired in HSCs in aging human individuals and patients with MDS and AML. We crossed Msh2-/- mice with animals carrying a heterozygous deletion of an upstream regulatory element of PU.1 (UREΔ/+). UREΔ/+Msh2-/- mice exhibited a significant, but very modest reduction of PU.1 expression on average by 26-37% in fractionated hematopoietic multipotent stem and myeloid progenitor cells. Strikingly, this minimal reduction of PU.1 led to the emergence of an aggressive, transplantable AML in more than two thirds of UREΔ/+Msh2-/- mice which was never observed in URE+/+Msh2-/- mice. Overt leukemia was preceded by a preleukemic phase hallmarked by an expanded population of multipotent murine hematopoietic stem cell enriched cells (HSPCs) that was myeloid-biased and less quiescent than their wild type counterpart. Longitudinal monitoring of preleukemic UREΔ/+Msh2-/- mice revealed a progressive increase in immature myeloid cells along with a gradual decrease in mature myeloid cells, as well as expansion of phenotypic HSPC compartments and multi-lineage dysplasia resembling human MDS. AML progression was accompanied by additional inhibition of a PU.1-cooperating factor, interferon responsive factor 8 (Irf8). Irf8 expression restoration rescued impaired expression of genes harboring PU.1/IRF consensus binding sites, led to the loss of aberrant self-renewal, promoted myeloid differentiation, and induced apoptosis in leukemic UREhetMsh2-/- cells demonstrating that Irf8 impairment functionally cooperates with minimally reduced PU.1 expression in our model. We also found evidence of disease-relevant joint PU.1/IRF8 inhibition in human myeloid leukemogenesis: (1) patients with MDS with a higher risk for the progression to AML had lower IRF8 levels; (2) lower IRF8 expression was detected specifically in AML patients with reduced PU.1 levels; (3) restoration of IRF8 expression induced differentiation in IRF8 low expressing AML cells, and (4) a positive correlation of PU.1 and IRF8 expression was found in human leukemia stem cells, but not in healthy HSCs. Strikingly, comparative pathway analysis revealed a genome-wide molecular resemblance of preleukemic and leukemic UREΔ/+Msh2-/- mice with gene expression profiles from human MDS and AML patients, respectively. Our study demonstrates that minimal reduction of a key lineage-specific transcription factor that commonly occurs in human disease is sufficient to initiate cancer development and provides mechanistic insight into the formation and progression of preleukemic stem cells in MDS and AML. Disclosures No relevant conflicts of interest to declare.

scholarly journals CGRP Signaling via CALCRL Increases Chemotherapy Resistance and Stem Cell Properties in Acute Myeloid Leukemia

2019 ◽  
Vol 20 (23) ◽  
pp. 5826 ◽  
Author(s):  
Tobias Gluexam ◽  
Alexander M. Grandits ◽  
Angela Schlerka ◽  
Chi Huu Nguyen ◽  
Julia Etzler ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Stem Cell ◽  
Mouse Model ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemic Cells ◽  
Hematopoietic Stem ◽  
Acute Myeloid

The neuropeptide CGRP, acting through the G-protein coupled receptor CALCRL and its coreceptor RAMP1, plays a key role in migraines, which has led to the clinical development of several inhibitory compounds. Recently, high CALCRL expression has been shown to be associated with a poor prognosis in acute myeloid leukemia (AML). We investigate, therefore, the functional role of the CGRP-CALCRL axis in AML. To this end, in silico analyses, human AML cell lines, primary patient samples, and a C57BL/6-based mouse model of AML are used. We find that CALCRL is up-regulated at relapse of AML, in leukemic stem cells (LSCs) versus bulk leukemic cells, and in LSCs versus normal hematopoietic stem cells. CGRP protects receptor-positive AML cell lines and primary AML samples from apoptosis induced by cytostatic drugs used in AML therapy, and this effect is inhibited by specific antagonists. Furthermore, the CGRP antagonist olcegepant increases differentiation and reduces the leukemic burden as well as key stem cell properties in a mouse model of AML. These data provide a basis for further investigations into a possible role of CGRP-CALCRL inhibition in the therapy of AML.

scholarly journals Evidence for malignant transformation in acute myeloid leukemia at the level of early hematopoietic stem cells by cytogenetic analysis of CD34+ subpopulations

Blood ◽  
1995 ◽  
Vol 86 (8) ◽  
pp. 2906-2912 ◽  
Author(s):  
D Haase ◽  
M Feuring-Buske ◽  
S Konemann ◽  
C Fonatsch ◽  
C Troff ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Malignant Transformation ◽  
Cell Sorting ◽  
Myeloid Leukemia ◽  
De Novo ◽  
Leukemic Cells ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract Acute myeloid leukemia (AML) is a heterogenous disease according to morphology, immunophenotype, and genetics. The retained capacity of differentiation is the basis for the phenotypic classification of the bulk population of leukemic blasts and the identification of distinct subpopulations. Within the hierarchy of hematopoietic development and differentiation it is still unknown at which stage the malignant transformation occurs. It was our aim to analyze the potential involvement of cells with the immunophenotype of pluripotent stem cells in the leukemic process by the use of cytogenetic and cell sorting techniques. Cytogenetic analyses of bone marrow aspirates were performed in 13 patients with AML (11 de novo and 2 secondary) and showed karyotype abnormalities in 10 cases [2q+, +4, 6p, t(6:9), 7, +8 in 1 patient each and inv(16) in 4 patients each]. Aliquots of the samples were fractionated by fluorescence-activated cell sorting of CD34+ cells. Two subpopulations, CD34+/CD38-(early hematopoietic stem cells) and CD34+/CD38+ (more mature progenitor cells), were screened for karyotype aberations as a marker for leukemic cells. Clonal abnormalities and evaluable metaphases were found in 8 highly purified CD34+/CD38-populations and in 9 of the CD34+/CD38-specimens, respectively. In the majority of cases (CD34+/CD38-, 6 of 8 informative samples; CD34+/CD38+, 5 of 9 informative samples), the highly purified CD34+ specimens also contained cytogenetically normal cells. Secondary, progression-associated chromosomal changes (+8, 12) were identified in the CD34+/CD38-cells of 2 patients. We conclude that clonal karyotypic abnormalities are frequently found in the stem cell-like (CD34+/CD38-) and more mature (CD34+/CD38+) populations of patients with AML, irrespective of the phenotype of the bulk population of leukemic blasts and of the primary or secondary character of the leukemia. Our data suggest that, in AML, malignant transformation as well as disease progression may occur at the level of CD34+/CD38-cells with multilineage potential.

MicroRNA Profiling of Human Acute Myeloid Leukemia and Normal Hematopoietic Stem/Progenitor Cells Reveals a Leukemia Stem Cell Signature.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 779-779
Author(s):  
Christopher Y. Park ◽  
Yulei Wang ◽  
Susan Prohaska ◽  
Diane Tseng ◽  
Irving L. Weissman
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Stem Cell ◽  
Myeloid Leukemia ◽  
Hematopoietic Stem ◽  
Supervised Clustering ◽  
Differentially Expressed Mirnas ◽  
Human Acute Myeloid Leukemia ◽  
Acute Myeloid

Abstract While numerous studies have contributed important insights into the molecular origins of human acute myeloid leukemia (AML), many may not accurately reflect molecular pathways critical to AML development or maintenance because they ignore the inherent heterogeneity among AML blasts. One subset of blasts - leukemia stem cells (LSCs) - exhibits the unique ability to self-renew and to engraft disease in immunodeficient mouse hosts, suggesting that their elimination is critical to developing curative therapies. In addition, there is little information regarding the role of microRNAs (miRNAs) in regulating gene expression or biologic function in AML. In order to assess the potential contribution of miRNAs to AML LSC biology, we have evaluated the expression profile of 315 mature miRNAs in FACS-purified AML LSC and compared it to both non-LSC blasts as well as normal human bone marrow (BM) derived hematopoietic stem cells (HSC) and committed progenitors using a multiplexed TaqMan-based real-time PCR strategy. SAM analysis with stringent criteria (at least 25% samples with Ct <30, FDR <1%) reveals that AML LSC and non-LSC blasts are more similar to one another than to normal HSC or committed progenitors. Among the BM populations tested, AML LSC and non-LSC populations are most similar to the granulocyte-macrophage progenitor (GMP). A set of miRNAs distinguishes AML LSC and non-LSC from normal HSC and committed progenitors, including 35 miRNAs that are under-expressed and 33 miRNAs that are over-expressed in both AML fractions versus the normal populations; many of these differentially expressed miRNAs show a range of expression exceeding 3 orders of magnitude. Supervised clustering analysis of AML LSC and non-LSC blasts reveals an LSC signature composed of 89 miRNAs, with nearly all differentially expressed miRNAs (86/89) exhibiting lower expression levels in AML LSC than non-LSC blasts. Finally, supervised clustering identifies a “stem-cell” signature composed of 17 miRNAs that are over-expressed in AML LSC and HSC versus committed progenitors. This group of miRNAs does not include miRNAs previously described as being highly expressed in embryonic stem cells. Together, these studies represent the first direct comparison of miRNA expression in a human cancer stem cell to its normal counterpart, thereby identifying miRNAs that may regulate AML LSC and/or normal HSC/committed progenitor function. Initial functional studies in vivo using LNA knockdown strategies indicate that a subset of miRNAs highly expressed in HSC and LSC is important in regulating normal HSC function. We are currently expanding these studies to test the role of these miRNAs in maintaining engrafted AMLs in the xenotransplant setting.

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