scholarly journals MLL-AF9 Initiates Transformation From Fast-Proliferating Myeloid Progenitors

2018 ◽  
Author(s):  
Xinyue Chen ◽  
Amaleah Hartman ◽  
Xiao Hu ◽  
Anna E. Eastman ◽  
Xujun Wang ◽  
...  

AbstractCancer is a hyper-proliferative clonal disease. Whether the proliferative state originates from the cell-of-origin or emerges later remains elusive. By tracking de novo transformation from normal hematopoietic progenitors expressing an acute myeloid leukemia (AML) oncogene MLL-AF9, we reveal that the cell cycle rate heterogeneity among granulocyte-macrophage progenitors (GMPs) determines their probability of transformation. An intrinsic fast cell cycle kinetics at the time of oncogene expression provide permissiveness for transformation, with the fastest cycling 3% of GMPs (∼0.006% of bone marrow nucleated cells) acquiring malignancy with nearly 100% efficiency. Molecularly, we propose that MLL-AF9 preserves the gene expression of the cellular states in which it is expressed. As such, when expressed in the naturally-existing, rapidly-cycling myeloid progenitors, this cell state is perpetuated, yielding malignancy. Our work elucidates one of the earliest steps toward malignancy and suggests that modifying the cycling state of the cell-of-origin could be an effective approach to prevent malignancy.


2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xinyue Chen ◽  
Daniel B. Burkhardt ◽  
Amaleah A. Hartman ◽  
Xiao Hu ◽  
Anna E. Eastman ◽  
...  

AbstractCancer is a hyper-proliferative disease. Whether the proliferative state originates from the cell-of-origin or emerges later remains difficult to resolve. By tracking de novo transformation from normal hematopoietic progenitors expressing an acute myeloid leukemia (AML) oncogene MLL-AF9, we reveal that the cell cycle rate heterogeneity among granulocyte–macrophage progenitors (GMPs) determines their probability of transformation. A fast cell cycle intrinsic to these progenitors provide permissiveness for transformation, with the fastest cycling 3% GMPs acquiring malignancy with near certainty. Molecularly, we propose that MLL-AF9 preserves gene expression of the cellular states in which it is expressed. As such, when expressed in the naturally-existing, rapidly-cycling immature myeloid progenitors, this cell state becomes perpetuated, yielding malignancy. In humans, high CCND1 expression predicts worse prognosis for MLL fusion AMLs. Our work elucidates one of the earliest steps toward malignancy and suggests that modifying the cycling state of the cell-of-origin could be a preventative approach against malignancy.





2010 ◽  
Vol 207 (3) ◽  
pp. 475-489 ◽  
Author(s):  
Yoon-Chi Han ◽  
Christopher Y. Park ◽  
Govind Bhagat ◽  
Jinping Zhang ◽  
Yulei Wang ◽  
...  

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.



Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 683-683
Author(s):  
Christopher Y. Park ◽  
Yoon-Chi Han ◽  
Govind Bhagat ◽  
Jian-Bing Fan ◽  
Irving L Weissman ◽  
...  

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.



Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 752-752
Author(s):  
Hao Wang ◽  
Stephan Lindsey ◽  
Iwona Konieczna ◽  
Elizabeth Horvath ◽  
Ling Bei ◽  
...  

Abstract HOX genes encode highly conserved homeodomain (HD) transcription factors and are arranged in four groups (A–D). During definitive hematopoiesis, HOX gene expression is activated 3′ to 5′ through each group. Therefore, HOX1-4 are actively transcribed in hematopoietic stem cells and HOX7-11 in committed progenitors. Under normal conditions, HoxA7-11 expression decreases during CD34+ to CD34− maturation. Abnormal Hox expression is characteristic of several poor prognosis subtypes of Acute Myeloid Leukemia (AML) including AML with translocations or duplications of the MLL gene. In such leukemias, expression of HoxB3, B4 and A7-11 is sustained in CD34−CD38+ cells. In murine bone marrow transplantation experiments, expression of MLL fusion proteins, HoxA9 or HoxA10 induces a myeloproliferative disorder (MPD) characterized by increased neutrophils (PMN). Over time, the mice progress to AML with circulating myeloid blasts. These results suggest overexpression of HoxA9 or HoxA10 is adequate for MPD, but differentiation block (AML) requires additional lesions. We found that HoxA9 and HoxA10 proteins not only decrease in expression during the CD34+ to CD34− transition, but also are tyrosine phosphorylated. In additional studies, we found that HoxA10 tyrosine phosphorylation state is relevant for differentiation stage-specific target gene expression during myelopoiesis. HoxA10 represses genes encoding phagocyte effector proteins in undifferentiated myeloid cells. During myelopoiesis, phosphorylation of conserved HD-HoxA10 tyrosines decreases binding to these genes, permitting phenotypic and functional differentiation. HoxA10 activates transcription of the gene encoding Mkp2 (Dusp4) in myeloid progenitors. Decrease in HoxA10-binding to this gene as differentiation proceeds decreases transcription and renders the cells susceptible to Jnk induced apoptosis. Therefore, we hypothesized that genetic lesions which influence post translational modification might cooperate with HoxA10 overexpression to lead from MPD to AML. In myeloid progenitors, HoxA10 is maintained in a non-phosphorylated state by SHP2 protein tyrosine phosphatase. SHP2 activity decreases as differentiation proceeds. Activating mutations in SHP2 have been described in AML. We found that such activated SHP2 mutants dephosphorylate HoxA10 through out ex vivo myelopoiesis. Therefore, we investigated cooperation between these two leukemia associated abnormalities in vivo. Mice were transplanted with bone marrow overexpressing HoxA10 (or empty vector control) with or without activated SHP2 (E76K). To control for SHP2 overexpression, other mice were transplanted with bone marrow overexpressing HoxA10 and wild type SHP2. Mice transplanted with bone marrow overexpressing HoxA10 (±SHP2) developed MPD which evolved to AML over 4 mos, consistent with previous observations. However, mice transplanted with bone marrow overexpressing HoxA10 and E76K SHP2 developed AML within 4 wks. This rapid development of AML correlated with abnormalities in expression of myeloid specific HoxA10 target genes. These studies indicate the importance of HoxA10 post translational modification for physiologically relevant function and identify cooperating lesions which may be significant for disease progression in human AML.



Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3839-3839
Author(s):  
Emilia Carolina Malafaia ◽  
A. Mario Marcondes ◽  
Ekapun Karoopongse ◽  
Daniele Serehi ◽  
Maria de Lourdes L. F. Chauffaille ◽  
...  

Abstract TWIST1, a basic helix-loop-helix (bHLH) transcription factor, plays a critical role in mesodermal development and organogenesis. Overexpressed TWIST1 has been thoroughly related to epithelial-mesenchymal transition (EMT) in solid tumors (QIN Q et al., 2012) and has been described as an emerging risk factor in hematological neoplasms (MERINDOL et al., 2014). . Many questions remain to be addressed concerning to the role of TWIST1 in acute myeloid leukemia (AML). The understanding of TWIST1 in leukemia cells and its interaction with microenvironment can offer new insights in regards to disease biology and therapeutic targets for patients with AML. Objectives: 1) to evaluate the role of stroma contact and hypoxia in TWIST1 expression in myeloid cell lines. 2) To evaluate the functional impact of overexpressing TWIST1 on KG1a and PL21 cells. 3) To evaluate TWIST1 expression in primary cells of AML patients. Methods: In order to mimic bone marrow microenvironment, myeloid cells were co-cultured with mesenchymal HS5 cell line and PO2 1% was established with Smart -Trak¨ 2 (Sierra Instruments, Inc.) equipment. Quantitative mRNA was determined using TaqMan¨ Universal Master Mix (Applied Biosystems, Foster City, CA) and 3-step standard cycling conditions with sequence-specific primer TWIST1 normalized to the expression of β-actin. KG1a and PL21 cells were transduced with lentivirus vector carrying e-GFP ("enhanced green fluorescence protein") for stable expression of TWIST1. Transduced cells were sorted by FITC fluorochrome and then verified through western blot analysis with TWIST1 antibody. For quantification of apoptosis, cells were labeled with PE-conjugated antibody using annexin V-phycoerythrin and propidium iodide (BD Biosciences, USA). DAPI (4',6- diamidino-2-phenylindole dihydrochloride) was used to stain DNA and determine cell cycle information . Apoptosis and cell cycle were analyzed by FACS -Becton Dickinson Canto II (BD Biosciences). Statistical analysis was assessed with unpaired t test. Results: Hypoxia induced TWIST1 mRNA expression in OCIAML3, PL21, KG1a and ML1 cell lines (fold-increased 46.3, 29.8, 12.9 and 2.3 respectively). Cells expressing endogenous TWIST1 protein (OCIAML3 and ML1) showed resistance to apoptosis in a hypoxic microenvironment (normoxia versus hypoxia: OCI/AML3, 22.6 % vs 11.7% and ML1, 29.8% vs. 7.5%) in contrast, cells not expressing endogenous TWIST1 protein (KG1a and PL21) went to apoptosis in the same conditions. Thus, overexpressing TWIST1 in KG1a and PL21 induced apoptosis protection in hypoxia (KG1a unmodified vs. modified: 17.6 ± 6.3 vs. 2.8 ± 6.3, p=0.04; PL21 unmodified vs. modified: 26.9 ± 10.9 vs. 3.2 ± 0.6, p=0.04) (fig 1). We found increased TWIST1 mRNA levels in bone marrow samples of 23 AML patients (3.88 ± 1.59) compared with 5 healthy controls (0.54 ±0.25) (p= 0.02) (fig 2). Patients in the highest tertile of TWIST1 expression did not show differences in percentage of blasts in bone marrow and complete remission after treatment compared with patients in low and middle tertile. Conclusion: Our data suggest TWIST1 gene expression protects acute myeloid leukemia cells from apoptosis in a hypoxic microenvironment. Moreover, our results showed increased expression of TWIST1 in AML patients. Thus, TWIST1 is a potential gene involved in leukemogenesis and should be further explored to understand disease biology and potential therapeutic targets. Disclosures No relevant conflicts of interest to declare.



2018 ◽  
Vol 1 (6) ◽  
pp. e201800153 ◽  
Author(s):  
Tanja Božić ◽  
Joana Frobel ◽  
Annamarija Raic ◽  
Fabio Ticconi ◽  
Chao-Chung Kuo ◽  
...  

De novo DNA methyltransferase 3A (DNMT3A) plays pivotal roles in hematopoietic differentiation. In this study, we followed the hypothesis that alternative splicing ofDNMT3Ahas characteristic epigenetic and functional sequels. SpecificDNMT3Atranscripts were either down-regulated or overexpressed in human hematopoietic stem and progenitor cells, and this resulted in complementary and transcript-specific DNA methylation and gene expression changes. Functional analysis indicated that, particularly, transcript 2 (coding for DNMT3A2) activates proliferation and induces loss of a primitive immunophenotype, whereas transcript 4 interferes with colony formation of the erythroid lineage. Notably, in acute myeloid leukemia expression of transcript 2 correlates with its in vitro DNA methylation and gene expression signatures and is associated with overall survival, indicating thatDNMT3Avariants also affect malignancies. Our results demonstrate that specificDNMT3Avariants have a distinct epigenetic and functional impact. Particularly, DNMT3A2 triggers hematopoietic differentiation and the corresponding signatures are reflected in acute myeloid leukemia.



Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1863-1863
Author(s):  
Gabriel Pineda ◽  
Kathleen M Lennon ◽  
Nathaniel P Delos-Santos ◽  
Florence Lambert-Fliszar ◽  
Gennarina L Riso ◽  
...  

Abstract Malignant reprogramming of progenitors into self-renewing cancer stem cells (CSCs) that have a predisposition for dormancy in protective niches has been implicated in therapeutic resistance of chronic myeloid leukemia (CML) and other CSC-driven malignancies. An unmet medical need for developing therapies that target niche dependent dormant human CSCs provides a compelling rationale for identifying key differences in gene expression at different cell cycle phases between normal and malignant progenitors in a CSC-supportive stromal co-culture system. Currently, few methods exist for quantifying cell cycle kinetics in live human leukemia stem cells (LSC). To date, efficient cell cycle transit time analysis in single live human leukemic progenitors derived from primary patient samples has been hampered by 1) decreased cell viability following transfection or transduction, 2) limited sample size, 3) dormancy of primitive progenitor populations thereby necessitating lentiviral rather than retroviral transduction and 4) increased apoptosis in the absence of a supportive microenvironment. To alleviate these challenges and improve transduction efficiency, we generated Fucci2BL, a lentiviral bicistronic reporter vector. Fucci2BL expresses mVenus-hGem(1/110) fused to mCherry-hCdt1(30/120) by the T2A peptide using an EF1 promoter that generates optimal levels of gene expression in progenitors. Initially, the reporter fidelity was characterized in 293A cells using flow cytometry and time-lapse confocal fluorescence microscopy. Time-lapse confocal fluorescence microscopy revealed normal cell morphology and distinct nuclear staining of either green or red fluorescence depending on the cell cycle stage. Once the fidelity of the Fucci2BL reporter was characterized, differences in gene expression levels between normal and malignant progenitors were analyzed. Whole transcriptome RNA-seq analysis revealed both cell cycle and DNA replication pathways were enriched in chronic phase CP (CML) compared to normal progenitors. Cell cycle kinetics between normal and chronic phase (CML) progenitors co-cultured in a niche were also analyzed using the Fucci2BL reporter. Normal progenitor cells on average transited the cell cycle within 26 hours while CP progenitor cells demonstrated a prolongation of transit through G1. In summary, the Fucci2BL system enables single transduction and single cell cycle tracking as well as gene expression changes in live primary progenitors in response to a niche. This robust lentiviral reporter can reproducibly distinguish cell cycle phases thereby providing an opportunity to quantitatively study the contribution of cell cycle kinetics to single cancer stem cell therapeutic resistance and to relapse. Disclosures Jamieson: J&J: Research Funding; GSK: Research Funding.



Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5316-5316
Author(s):  
Bing Xu ◽  
Huijuan Dong ◽  
Feili Chen ◽  
Yong Zhou ◽  
Jiabao Liang ◽  
...  

Abstract Background: I-mfa has been identified as an inhibitor of MyoD and other related myogenic basic helix-loop-helix proteins. I-mfa contains a cysteine-rich C-terminal domain, and has been reported to function as transcriptional regulator of different pathways including Wnt signaling, c-jun N-terminal kinase signaling, and the regulatory properties of I-mfa depend on the C-terminal domain. Furthermore, recent studies have found that the I-mfa domain may have a close correlation with the development of myeloid neoplasms, however the role of I-mfa in adult patients with de novo acute myeloid leukemia still remain unclear. Aims: The aim of this study was to determine I-mfa expression in adult patients with de novo acute myeloid leukemia and its clinical significance. Methods: BM samples form 110 adult patients with de novo AML were analyzed. Of the 110 AML patients, 66 were males and 44 were females, with a mean age of 32 years( range from 12 to 77 years). Among them, 1 out of 110 patients was M1, 49 were M2, 14 were M4, 28 were M5, 1was M6 and 17 were acute unclassified leukemia. All patients received 1 to 2 cycles of induction of standard-dose cytarabine continuous infusion×7 days with idarubicin or daunorubicin×3days, fellowed by consolidation therapy with HiDAC and then stem cell transplantation according to patient’s condition. Real-time reverse transcription-polymerase chain reaction(RT-PCR) was used to detect the expression of I-mfa gene in 110 de novo adult AML patients, and the patients were divided into high and low I-mfa expression groups accordint to the median expression of I-mfa mRNA. Comparisons were performed using Mann-Whitney U test, Chi-square test and Kaplan-Meier method. Results:Distribution of I-mfa gene expression in different FAB subtypes was with no significant differences (P=0.169). The median age of AML pateints in low and high I-mfa gene epxression groups were 35 and 40 years old(P=0.162), and the median expression of I-mfa in 44 female patients and 66 male patients was 0.018 and 0.013 separately(P=0.728). What’s more, there was no significant difference of WBC, Hb level, PLT, bone marrow blast counts between the two groups (P>0.05), and the I-mfa expression level was also not correlated with chromosome risk stratification and the expression of CD34 (P>0.05). High I-mfa expression group had a lower complete remission rate than that in the low expression group (81.8% vs 63.6%, P=0.032), However, the overall survival rate was with no significant difference in the low and hign I-mfa gene expression groups(76.4% vs 76.4%, P=0.471). Conclusions: Our results showed high I-mfa expression correlates with a poor treatment response, the OS rate was with no significant difference in the two groups. There is somewhat correlation between the expression level of I-mfa gene and prognosis and the expression of I-mfa may be a prognostic factor for adult patients with de novo acute myeloid leukemia. Disclosures No relevant conflicts of interest to declare.



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