PML-RARα Deregulates an Unexpectedly Small Number of Genes in Pre-Leukemic Promyelocytes

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3526-3526
Author(s):  
Coline M Gaillard ◽  
Taku A Tokuyasu ◽  
Emmanuelle Passegué ◽  
Scott C. Kogan
Keyword(s):  
Bone Marrow ◽  
Fusion Protein ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Leukemic Cells ◽  
Cytokine Signaling ◽  
Proliferation Capacity ◽  
Number Of Genes

Abstract Abstract 3526 Background: Acute Promyelocytic Leukemia (APL) is characterized by the accumulation in the blood and bone marrow of abnormal promyelocytes, which have the ability to transfer the disease to secondary recipients in animal models. The PML-RARα fusion protein is thought to be the primary abnormality implicated in the pathology, and is believed to prevent transcription of genes necessary for normal myeloid development and differentiation. Identifying PML-RARα targets is critical for understanding the road to leukemic transformation. However, such targets have so far been identified using cell line assays in vitro, murine cells differentiated into promyelocytes in vitro, or fully transformed murine or human leukemic cells. Focusing on the cell population in which the transforming potential is acquired, we describe here a novel strategy to identify the transcriptomic dysregulation induced by PML-RARα expression in maturing myeloid populations in vivo. Methods: We utilize a murine model of human APL in which the human PML-RARα fusion gene is expressed under the control of the MRP8 promoter, driving its expression in maturing myeloid populations. Those animals can be described as pre-leukemic since they eventually develop leukemia when additional mutations occur. Fresh bone marrows from normal (Fvb/n) or pre-leukemic (PML-RARα) animals were harvested. Using an improved cell surface antigen staining strategy and fluorescence-activated cell sorting, three populations of increasingly differentiated myeloid populations have been sorted (Granulocyte Macrophage Progenitor, Early promyelocyte and Late promyelocyte). RNA was extracted and submitted for whole-genome microarray analysis. In addition, we are using a variety of bioinformatics approaches to decipher the network of novel interactions driven by PML-RARα expression. Results: Markers used in our sorting strategy were validated in the dataset, including CD34 and Gr1. In the normal samples, markers of neutrophil maturation increased, largely as expected, and a number of early transcription factors decreased in an expected manner including Hoxa9 and Meis1. One remarkable finding was that despite the previously described ability of PML-RARα to regulate transcription from multiple sites in the genome, only a small number of genes were differentially impacted by the expression of this protein. Surprisingly, well-known regulators of myeloid differentiation that have been implicated in the retinoic acid responsiveness of APL including Sfpi1 (PU.1) and Cebpa were not differentially expressed. However, in pre-leukemic samples PML-RARα did cause decreased expression of multiple neutrophilic granule genes including Ltf, Mmp9 and Ngp. The gene most upregulated in the pre-leukemic samples was Spp1 which encodes the osteopontin phosphoprotein. Of interest, we identified the myeloid tumor suppressor Irf8 to be downregulated 5 fold in the presence of PML-RARα. To investigate the importance of IRF8 levels in APL initiation, we transplanted Irf8+/+ PML-RARα or Irf8+/− PML-RARα bone marrow into irradiated recipients. Despite the potential for decreased expression of IRF8 to contribute to APL, we observed no difference. This result does not confirm a role for IRF8 in APL pathogenesis, but further investigations are needed to exclude such a role. Bioinformatics studies highlighted enrichment in cell cycle-related genes upon PML-RARα expression, suggesting a possible difference in the proliferation capacity of the pre-leukemic cells, which is currently under investigation. Conclusions: We found that in vivo the transcriptome was only modestly dysregulated by the presence of PML-RARα. These observations open up new questions on the role of the fusion protein in pathogenesis: How does PML-RARα prime pre-leukemic cells for full transformation? How do secondary events allow an initiated cell to advance to a fully transformed state? Such questions are currently being investigated, with a special interest on looking at the cooperation between PML-RARα and activated cytokine signaling in leukemia initiation. Disclosures: No relevant conflicts of interest to declare.

Identification of Non-Cardiotoxic hERG1 Blockers to Overcome Chemoresistance in Acute Lymphoblastic Leukemias

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1506-1506
Author(s):  
Marika Masselli ◽  
Serena Pillozzi ◽  
Massimo D'Amico ◽  
Luca Gasparoli ◽  
Olivia Crociani ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Mouse Model ◽  
Map Kinases ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Significant Proportion ◽  
Leukemic Cells ◽  
K Channel

Abstract Abstract 1506 Although cure rates for children with acute lymphoblastic leukemia (ALL), the most common pediatric malignancy, have markedly improved over the last two decades, chemotherapy resistance remains a major obstacle to successful treatment in a significant proportion of patients (Pui CH et al. N Engl J Med., 360:2730–2741, 2009). Increasing evidence indicates that bone marrow mesenchymal cells (MSCs) contribute to generate drug resistance in leukemic cells (Konopleva M et al., Leukemia, 16:1713–1724, 2002). We contributed to this topic, describing a novel mechanism through which MSCs protect leukemic cells from chemotherapy (Pillozzi S. et al., Blood, 117:902–914, 2011.). This protection depends on the formation of a macromolecular membrane complex, on the plasma membrane of leukemic cells, the major players being i) the human ether-a-gò-gò-related gene 1 (hERG1) K+ channel, ii) the β1integrin subunit and iii) the SDF-1α receptor CXCR4. In leukemic blasts, the formation of this protein complex activates both the ERK 1/2 MAP kinases and the PI3K/Akt signalling pathways triggering antiapoptotic effects. hERG1 exerts a pivotal role in the complex, as clearly indicated by the effect of hERG1 inhibitors to abrogate MSCs protection against chemotherapeutic drugs. Indeed, E4031, a class III antiarrhythmic that specifically blocks hERG1, enhances the cytotoxicity of drugs commonly used to treat leukemia, both in vitro and in vivo. The latter was tested in a human ALL mouse model, consisting of NOD/SCID mice injected with REH cells, which are relatively resistant to corticosteroids. Mice were treated for 2 weeks with dexamethasone, E4031, or both. Treatment with dexamethasone and E4031 in combination nearly abolished bone marrow engraftment while producing marked apoptosis, and strongly reducing the proportion of leukemic cells in peripheral blood and leukemia infiltration of extramedullary sites. These effects were significantly superior to those obtained by treatment with either dexamethasone alone or E4031 alone. This model corroborated the idea that hERG1 blockers significantly increase the rate of leukemic cell apoptosis in bone marrow and reduced leukemic infiltration of peripheral organs. From a therapeutic viewpoint, to develop a pharmacological strategy based on hERG1 targeting we must consider to circumvent the side effects exerted by hERG1 blockers. Indeed, hERG1 blockers are known to retard the cardiac repolarization, thus lengthening the electrocardiographic QT interval, an effect that in some cases leads to life threatening ventricular arrhythmias (torsades de points). On the whole, it is mandatory to design and test non-cardiotoxic hERG1 blockers as a new strategy to overcome chemoresistance in ALL. On these bases, we tested compounds with potent anti-hERG1 effects, besides E4031, but devoid of cardiotoxicity (e.g. non-torsadogenic hERG1 blockers). Such compounds comprise erythromycin, sertindole and CD160130 (a newly developed drug by BlackSwanPharma GmbH, Leipzig, Germany). We found that such compounds exert a strong anti-leukemic activity both in vitro and in vivo, in the ALL mouse model described above. This is the first study describing the chemotherapeutic effects of non-torsadogenic hERG1 blockers in mouse models of human ALL. This work was supported by grants from the Associazione Genitori contro le Leucemie e Tumori Infantili Noi per Voi, Associazione Italiana per la Ricerca sul Cancro (AIRC) and Istituto Toscano Tumori. Disclosures: No relevant conflicts of interest to declare.

A Novel Strategy for Expanding Primitive Leukemic Cells from Chronic Phase CML Patients by Forced Overexpression of a NUP98-HOXA10 Homeodomain Fusion Gene.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1078-1078
Author(s):  
Ivan Sloma ◽  
Suzan Imren ◽  
Yun Zhao ◽  
Keith Humphries ◽  
Connie J. Eaves
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Cells ◽  
Fusion Gene ◽  
Low Frequency ◽  
Chronic Phase ◽  
Leukemic Cells ◽  
Human Cord Blood ◽  
Hematopoietic Stem

Abstract Analysis of the leukemic stem cell compartment in CML patients with chronic phase disease remains a major challenge. This is due to the usually low frequency of these cells in the bone marrow and blood of most patients regardless of the WBC count and the fact that they are typically outnumbered by normal hematopoietic stem cells from which they cannot be currently separated. Moreover, thus far it has not been possible to identify conditions for their selective expansion in vitro or in vivo. To pursue this goal, we have begun to explore the effects of certain HOX gene-containing constructs on primitive chronic phase CML cells based on previous evidence that these genes markedly enhance the expansion of primitive normal murine and human cord blood cell numbers without inducing leukemia. Lineage-negative peripheral blood or bone marrow cells from 3 chronic phase CML patients (with >93%, <20% and <6% Ph+ LTC-ICs by G-banding karyotyping) were pre-stimulated overnight in a medium containing a serum substitute and 100 ng/ml hSteel Factor (SF), 100 ng/ml hFlt3-ligand and 20 ng/ml each of hIL-3, hIL-6 and hG-CSF. Cells were then exposed to a lenti-PGK-GFP virus with or without an upstream MDUS-NUP98-HOXA10 homeodomain (HD) element for 5 hours in the same medium. After removal of the virus, the cells were maintained in culture under the same conditions for 2 more days to allow full expression of the transduced genes. At this point, both cultures contained the same number of total cells, GFP+ cells and clonogenic progenitors (BFU-E + CFU-GM + CFU-GEMM); i.e., 2.2±0.5 x105 vs 2.2±0.6 x105 total cells, 1.0±0.2 x105 vs 1.3±0.3 x105 GFP+ cells, 3.6±1.7 x104 vs 3.4±1.7 x104 total CFCs and 1.7±0.9 x104 vs 2.4±1.3 x104 GFP+ CFCs per 105 starting lin- cells. However, after the 2-day post-transduction, cells had been maintained for 6 weeks in longterm cultures (LTCs) containing murine stromal cells producing hIL-3, hSF and hG-CSF, we noted a markedly higher (4 to 74-fold) output of CFCs from the NUP98-HOXA10HD-transduced cells. Moreover, whereas the proportion of GFP+ CFCs in the 2-day post-transduction cultures was on average only 31% and 48 % for the control and tested cells respectively, this increased to >98% in the 6-week LTCs initiated with cells that were overexpressing NUP98-HOXA10HD but remained constant at 39% in the control LTCs - suggesting a significant growth advantage conferred by the NUP98A10HD transgene. Importantly, RT-PCR genotyping of the colonies in these assays showed the majority of LTC-IC-derived CFCs from the NUP98-HOXA10HD-transduced cells to be BCR-ABL+, indicative of an even greater output of CFCs by the NUP98-HOXA10HD transduced BCR-ABL+ vs normal cells. These results highlight the potential of NUP98-HOXA10HD to selectively expand primitive CML cells isolated directly from chronic phase patients which will facilitate their further investigation and use to screen and validate new therapeutic agents.

Distinct Metabolic Dependency of Normal and Leukemic Cells in a Mouse Model

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 759-759
Author(s):  
Rushdia Z. Yusuf ◽  
Sanket S. Acharya ◽  
Vionnie Yu ◽  
Borja Saez ◽  
Mildred Duvet ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Tca Cycle ◽  
Leukemic Cells ◽  
Mouse Bone Marrow ◽  
Metabolomic Profiling ◽  
Glycolysis Pathway ◽  
Rate Limiting

Abstract Abstract 759 We hypothesized that metabolic differences between leukemia initiating cells and their normal counterparts represent a vulnerability in the leukemia initiating cell, which can be therapeutically exploited. To test this hypothesis, we used the MLL-AF9 acute myeloid leukemia (AML) model in mice. Actin-DsRed mouse bone marrow transduced with MLL-AF9 expressing retrovirus was used to produce serially transplantable leukemia. Leukemic granulocyte-monocyte precursors (L-GMPs), defined by others to be the leukemia initiating cells were flow sorted from secondary recipient mice and compared with normal GMPs (N-GMPs) from actin Ds-Red mice. Gene expression profiling, metabolomic profiling via liquid chromatography- mass spectrometry and an in vitro shRNA screen were used to identify metabolic pathways preferentially activated in leukemia initiating cells. Of 1574 defined metabolic enzymes, 44 were found to be differentially expressed between L-GMPs and their normal counterparts (N-GMPs). These together with 117 classic rate limiting enzymes were subjected to shRNA knockdown in vitro. Metabolomic profiling of both cell populations was used to corroborate findings from shRNA knockdowns. L-GMPs and N-GMPs were transduced with lentivirus expressing shRNAs of interest (5 shRNAs per gene) in a 384 well format, selected with puromycin and cultured for 72–96 hours in the presence of GFP-positive primary bone marrow stroma. The number of cells in each well at the end of this experiment was quantitated using an Image Xpress microscope. Genes, the knockdown of which by at least two independent shRNAs produced a two fold or more decrease in L-GMPs as compared to control wells and did not similarly decrease N-GMPs, were chosen for in vivo validation. Ten genes in the glycolysis pathway and TCA cycle, fatty acid metabolism and detoxification, and ketohexokinase were identified. Ketohexokinase, a rate-limiting enzyme in fructose metabolism was particularly potent and of interest given its potential to be exploited therapeutically. In vivo assessment of its relative ability to inhibit malignant versus normal hematopoietic cells is ongoing. These studies provide preliminary support for the hypothesis that specific metabolic circuits are differentially active in leukemia initiating cells in MLL-AF9 AML and may represent unique points of vulnerability that can be targeted therapeutically. Authors 1 and 2 contributed equally. Authors 3 and 4 contributed equally. Disclosures: No relevant conflicts of interest to declare.

Potent Cooperation Between NUP98-NSD1 and FLT3-ITD In AML Induction

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3797-3797
Author(s):  
Angeliki Thanasopoulou ◽  
Alexandar Tzankov ◽  
Juerg Schwaller
Keyword(s):  
Bone Marrow ◽  
Fusion Protein ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Latency Period ◽  
Histopathological Analysis ◽  
Murine Bone Marrow ◽  
Marrow Cells

Abstract The NUP98-NSD1 fusion protein, product of the t(5;11)(q35;p15.5) chromosomal translocation, is an AML-associated cytogenetically silent genetic aberration, recently identified as the most frequent fusion in pediatric AML, generally associated with aggressive disease and poor prognosis. Interestingly, the vast majority (>70%) of the reported NUP98-NSD1-positive cases also carried an activating FLT3-ITD mutation suggesting functional cooperation. The purpose of this study was to search for experimental evidence of a functional cooperation between NUP98-NSD1 and FLT3-ITD in the transformation of murine hematopoietic cells in vitro and in vivo. Lineage surface marker-depleted murine bone marrow cells were transduced with either pMSCV-NUP98-NSD1-neo or pMSCV-FLT3-ITD-GFP or both expression constructs on fibronectin-coated plates. Serial colony formation assays in myeloid favoring medium and immunophenotypic analysis by flow cytometry indicated that retroviral expression of NUP98-NSD1 provided increased self-renewal capacity and impaired differentiation of murine bone marrow stem and progenitor cells. NUP98–NSD1 expressing cells displayed a typical myeloblastic morphology and co-expressed myeloid and early stem cell surface markers (CD34low/c-kit+/FcgR+/Gr-1+/ Mac-I+/B220-). Co-expression of FLT3-ITD resulted in high rates of cell proliferation, showed a more differentiated phenotype and concomitantly impaired the in vitro clonogenic capacity in methylcellulose cultures. Bone marrow cells expressing NUP98-NSD1 with or without FLT3-ITD were harvested from methylcellulose cultures and transplanted into sub-lethally irradiated syngeneic mice. All mice receiving cells co-expressing NUP98-NSD1 and FLT3-ITD developed AML that was transplantable into all secondary recipients. Myeloid leukemic blasts that co-expressed NUP98-NSD1 and FLT3-ITD were present in abundance both in BM preparations and in blood smears, and histopathological analysis showed widespread infiltration into solid organs. By contrast, no AML ever developed in mice receiving cells expressing only NUP98-NSD1. These mice, similar to mice receiving cells expressing FLT3-ITD only, developed signs of a chronic myeloproliferative disorder, characterized by expansion of Mac-1+/Gr-1+ BM cells with granulocytic/monocytic differentiation that in some cases caused severe distress after a latency period of more than one year. Intriguingly, upon injection with double transduced NUP98-NSD1 and FLT3-ITD progenitors rather different latency periods of the AML development were observed between different experiments. Interestingly, the latency periods could be correlated to the ratio of expression levels of FLT3-ITD to wildtype FLT3, with higher FLT3-ITD levels associated with a shorter latency. To further investigate the significance of aberrant FLT3 signaling, in vitro and in vivo transformed NUP98-NSD1 and NUP98-NSD1/FLT3-ITD cells were treated with a selective FLT3 tyrosine kinase inhibitor (PKC412). The higher sensitivity of cells co-expressing NUP98-NSD1 and FLT3-ITD to PKC412, compared to cells expressing NUP98-NSD1 only, indicated that proliferation and survival were dependent on FLT3-derived signals. Taken together, these observations demonstrate a potent cooperation between NUP98-NSD1 fusion and FLT3-ITD in leukemic transformation. However, neither the NUP98-NSD1 fusion protein nor the FLT3-ITD mutation alone was sufficient to induce AML. Moreover, the high sensitivity of NUP98-NSD1 and FLT3-ITD co-expressing leukemic blasts to FLT3 signaling inhibition suggests a possible therapeutic strategy to be further explored in this AML subgroup. Disclosures: No relevant conflicts of interest to declare.

The PAF Complex Regulation of Prmt5 Facilitates Leukemic Progression

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3914-3914
Author(s):  
Justin Serio ◽  
Wei Chen ◽  
Maria Mysliwski ◽  
Lili Chen ◽  
James Ropa ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Conflicts Of Interest ◽  
Leukemic Cell ◽  
Leukemic Cells ◽  
Cytokine Signaling ◽  
Cycle Arrest ◽  
Acute Myeloid

Abstract Acute myeloid leukemias have been linked with dysregulated epigenetic landscapes sometimes attributed to altered functions of epigenetic regulators. The Polymerase-Associated Factor complex (PAFc) is an epigenetic regulator involved in transcriptional initiation, elongation and termination and directly interacts with the CTD of RNA Pol II. The complex is comprised of 6 subunits in human cells, Paf1, Cdc73, Ctr9, Leo1, Rtf1 and Ski8. Many of these subunits have key roles in a variety of cancers including acute myeloid leukemia (AML). We have previously shown the relevance of the PAFc in MLL-rearranged leukemias where its interaction with MLL fusion-proteins is required for leukemic progression in vitro and in vivo (Muntean et al. 2013 Blood, Muntean et al. 2010 Cancer Cell). However, little is known about the gene programs controlled by the PAFc and how these contribute to leukemogenesis. Here we identify Prmt5, an arginine methyltransferase, as a direct downstream target gene of the PAFc. Prmt5 is upregulated in variety of cancers and has been linked to cell cycle progression and activation of known oncoproteins. In addition, Prmt5 has been implicated in AML and is essential for normal hematopoiesis where loss of Prmt5 induces bone marrow aplasia due to impaired cytokine signaling (Tarighat et al. 2015 Leukemia, Liu et al. 2015 J Clin Invest). Our work establishes a major role for the PAFc in regulating Prmt5 expression in AML. We observe that excision of the Cdc73 subunit of the PAFc results in reduced proliferation, the induction of differentiation, cell cycle arrest, and a mild increase in apoptosis. Several key epigenetic marks are reduced globally upon loss of Cdc73 including H4R3me2s, a modification catalyzed by Prmt5. RNA sequencing and bioinformatics analysis using GSEA, revealed that loss of Cdc73 led to increased expression of a gene program associated with hematopoietic differentiation, in agreement with our cellular characterization. In addition, the downregulation of a methyltransferase gene program was detected upon Cdc73 excision. Included in this signature were several members of the Prmt family. Analysis of changes in expression following loss of Cdc73 and functional relevance in MLL-AF9 leukemic cells led us to Prmt5 as a gene critically important in AML cells and modulated by the PAFc. To interrogate the function of Prmt5 in AML cells, we performed shRNA knockdown experiments which resulted in reduced proliferation, reduced cell fitness, G1 cell cycle arrest and global reduction H4R3me2s. ChIP experiments revealed that the PAFc localizes to the Prmt5 locus in mouse and human derived leukemic cells. Further, preliminary data suggests the MLL-AF9 fusion protein also localizes to the Prmt5 locus and may enhance its transcriptional output. The enzymatic activity of Prmt5 is necessary for AML cell growth as wild type PRMT5 can rescue proliferation of Prmt5 knock-down cells while a catalytic dead mutant cannot. Furthermore, we have observed that knockdown of Prmt5 increases the disease latency of Hoxa9/Meis1 induced leukemia in vivo. Utilizing a commercially available inhibitor for Prmt5, EPZ015666 (Chan-Pembre et al. 2015 Nat Chem Bio), we show pharmacologic inhibition of PRMT5 reduces the growth of a spectrum of human leukemic cell lines, suggesting PRMT5 is important for multiple subtypes of AML. Overall, our findings elucidate the PAFc as a regulator of Prmt5 expression that is necessary for the maintenance of AML. Disclosures No relevant conflicts of interest to declare.

Effects of MiR-451a on the Phagocytosis and Polarization of Macrophages

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 42-42
Author(s):  
Xiaoli Liu ◽  
Dongyue Zhang ◽  
Hao Wang ◽  
Qian Ren ◽  
Lina Wang ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Microrna Expression ◽  
Differentially Expressed ◽  
Proliferation Capacity ◽  
Microrna Sequencing ◽  
Differentiation Marker

Macrophages are important member in tissue microenvironments and play diverse physiologic and pathologic roles. Leukemia associated macrophages (LAM) are a kind of specifically activated macrophages in leukemia microenvironment, which are different from M1, M2 and TAMs. We have reported the heterogeneities in gene expression profiles of LAMs. However, MicroRNA expression profiles of LAMs and regulatory mechanism are still unknown. Here, a MLL-AF9 induced mouse acute myeloid leukemia (AML) model was used, and LAMs in the spleen and bone marrow were sorted for microRNA sequencing. The microRNA expression profiles of LAMs in bone marrow and spleen in AML mice were different from macrophages from control mice. Based on the volcano plot, more than 100 microRNAs were differentially expressed in LAMs compared with macrophages in control mice. Next, five differentially expressed microRNAs were selected and verified by qRT-PCR in LAMs from spleen. The results showed that miR-451a and miR-155-5p in spleen LAMs were significantly upregulated in LAMs from spleen. Overexpression of miR-451a altered the morphology of macrophages, enhanced the phagocytic ability of macrophages, and promotes the expression of macrophage differentiation marker CD11b. Furthermore, overexpression of miR-451a had little effect on M0 macrophages, but increased the proliferation capacity of macrophages upon stimulation toward M1 or M2 phenotype. MiR-451a overexpressed-macrophages had higher level of iNOS when stimulated with LPS or IL-4 whereas there was no difference in the expression of IL-1β, IL-6, CD206 and Arg-1 between MiR-451a overexpressed-macrophages and control macrophage. Therefore, our data revealed the characteristics of the microRNA expression profile of LAMs for the first time, and verified the effect of miR-451a on macrophage in vitro. Disclosures No relevant conflicts of interest to declare.

MLL-AF9 and MLL-ENL Induce Deregulation of Similar Downstream Candidate Genes: An Analysis across Experimental Protocols and Laboratories.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3372-3372
Author(s):  
Ashish R. Kumar ◽  
Robert K. Slany ◽  
Jay L. Hess ◽  
John H. Kersey
Keyword(s):  
Gene Expression ◽  
Fusion Protein ◽  
Fusion Gene ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Expression Systems ◽  
Rt Pcr ◽  
Conditional Expression

Expression profiling has become an important tool for understanding gene deregulation in MLL-fusion leukemias. However, the results of gene profiling experiments are difficult to interpret when applied to leukemia cells because (i) leukemias arise in cells that differ greatly in their gene expression profiles, and (ii) leukemias most often require secondary genetic events in addition to the MLL fusion gene. Two principal model systems have been used to understand the direct effects of MLL-fusion genes. Knock-in models have the advantage of the fusion gene being under control of the physiologic promoter. On the other hand, conditional expression systems offer the ability to conduct short term experiments, permitting the analysis of direct effects on downstream genes. In the present combined-analysis, we used the Affymetrix U74Av2 oligonucleotide microarray to evaluate the effects of the MLL-fusion gene in vivo and in vitro respectively using two closely related MLL fusion genes - MLL-AF9 for knock-in and MLL-ENL for conditional expression. In the MLL-AF9 study, we compared gene expression profiles of bone marrow cells from MLL-AF9 knock-in mice (C57Bl/6, MLL-AF9+/−) to those of age-matched wild type mice (Kumar et. al. 2004, Blood). We used a t-test (p<0.05) to selected genes that showed significant changes in expression levels. In the MLL-ENL study, we transformed murine primary hematopoietic cells with a conditional MLL-ENL vector (MLL-ENL fused to the modified ligand-binding domain of the estrogen receptor) such that the fusion protein was active only in the presence of tamoxifen. We then studied the downstream effects of the fusion protein by comparing gene expression profiles of the cells in the presence and absence of tamoxifen. We used a pair-wise comparison analysis to select genes that showed a change in expression level of 1.5 fold or greater in at least two of three experiments (Zeisig et. al. 2004, Mol. Cell Biol.). Those genes that were up-regulated in both datasets were then compiled together. This list included Hoxa7, Hoxa9 and Meis1. The results for these 3 genes were confirmed by quantitative RT-PCR in both the MLL-AF9-knock-in and the MLL-ENL-conditional-expression systems. The remaining candidate genes in the common up-regulated gene set (not yet tested by quantitative RT-PCR) include protein kinases (Bmx, Mapk3, Prkcabp, Acvrl1, Cask), RAS-associated proteins (Rab7, Rab3b), signal transduction proteins (Notch1, Eat2, Shd, Fpr1), cell membrane proteins (Igsf4), chaperones (Hsp70.2), transcription factors (Isgf3g), proteins with unknown functions (Olfm1, Flot1), and hypothetical proteins. The results of the combined analysis demonstrate that these over-expressions are (i) a direct and sustained effect of the MLL-fusion protein, (ii) are independent of secondary events that might be involved in leukemogensis, and (iii) are independent of the two partner genes that participate in these fusions. The over-expression of a few genes in both the -in vitro and in vivo experimental systems makes these molecules very interesting for further studies, to understand the biology of MLL-fusion leukemias and for development of new therapeutic strategies.

FIP1L1/PDGFRa Synergizes with SCF/c-Kit Signaling To Induce Systemic Mastocytosis in a Chronic Eosinophilic Leukemia Murine Model

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1540-1540
Author(s):  
Yoshiyuki Yamada ◽  
Jose A. Cancelas ◽  
Eric B. Brandt ◽  
Abel Sanchez-Aguilera ◽  
Melissa McBride ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Small Intestine ◽  
Murine Model ◽  
Fusion Gene ◽  
Systemic Mastocytosis ◽  
Wild Type ◽  
Chronic Eosinophilic Leukemia

Abstract Systemic mastocytosis (SM) associated with chronic eosinophilic leukemia (CEL)/hypereosinophilic syndrome (HES) is a result of expression of the Fip1-like1 (FIP1L1)/platelet-derived growth factor receptor alpha (PDGFRa) (F/P) fusion gene. We have previously described a murine CEL/HES model (CEL-like mice) induced by F/P fusion gene transduction and T-cell overexpression of IL-5 (Yamada Y et al., Blood 2006). We have now validated a preclinical murine model of F/P-induced SM/CEL and analyzed the pathogenesis of SM in this model. F/P+ mast cells (MC, defined as EGFP+/c-kit+/FceRI+) were significantly increased in the small intestine, bone marrow (BM) and spleen of CEL-like mice compared to wild-type mice (Table). CEL-like mice also developed cutaneous MC infiltration. In addition, mMCP-1 serum levels, which correlate well with MC expansion and activation in vivo, were significantly higher in CEL-like mice than in wild-type mice (64,000 ± 23,800 and 38 ± 41.4 pg/ml, respectively). F/P induces increased expansion of BM-derived MC in vitro (∼2,000-fold) and F/P+ BM-derived MC survive longer than wild-type MC in cytokine-deprived medium (28.0 ± 2.3% vs. 8.7 ± 3.1% 7AAD−/Annexin V− cells after 48 hours). This correlated with increased Akt phosphorylation in the F/P+ MC. Since c-kit mutations are the most frequent cause of SM, we analyzed the possible synergistic role of SCF and F/P signaling. F/P and SCF/c-kit signaling indeed synergize in the development of BM-derived MC (16-fold greater expansion than in the absence of SCF) and F/P+ BM-derived MC showed a 3.7-fold greater migratory response to SCF than wild-type BM-derived MC. In order to determine the role of SCF/c-kit signaling in F/P+ MC development, activation and tissue infiltration in vivo,these responses were evaluated in mice that were treated with a blocking anti-c-kit blocking antibody, ACK-2, or an isotype-matched control antibody. ACK-2 treatment suppressed intestinal MC infiltration and elevated plasma levels of mMCP-1 induced by F/P expression by 95 ± 6.0% and 98 ± 0.76%, respectively, whereas MC and plasma mMCP-1 were completely undetectable in wild-type mice treated with ACK2. This suggests that SCF/c-kit interactions may synergize with F/P to induce SM. In summary, mice with CEL-like disease also develop SM. F/P-induced SM is a result of increased in vivo MC proliferation, survival, activation and tissue infiltration. SCF/c-kit signaling synergizes with F/P in vivo and in vitro to promote mast cell development, activation and survival. EGFP+/c-kit+/FcεRI+ cell frequency in tissues of control and CEL-like mice (%) Control mice CEL-like mice Small intestine 1.0±0.95 47±21.4* Bone marrow 0.2±0.14 3±1.9* Spleen 0.05±0.01 3±0.8*

Thrombopoietin Stimulation Leads to Enhanced Polyploidization in p53-/- Bone Marrow Megakaryocytes: In Vivo and in Vitro Studies.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2531-2531
Author(s):  
Pani A. Apostolidis ◽  
Stephan Lindsey ◽  
William M. Miller ◽  
Eleftherios T. Papoutsakis
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Platelet Surface ◽  
Platelet Counts ◽  
Reticulated Platelets ◽  
High Ploidy ◽  
And Control ◽  
Platelet Formation

Abstract Abstract 2531 Poster Board II-508 BACKGROUND AND HYPOTHESIS. We have previously shown that tumor suppressor p53 is activated in differentiating megakaryocytic (Mk) cells and its knock-down (KD) leads to increased polyploidization and delayed apoptosis in CHRF, a human Mk cell line. Furthermore, bone marrow (BM)-derived Mks from p53−/− mice reach higher ploidy classes in culture. Accordingly, we hypothesized that the role of p53 during megakaryopoiesis is to delimit polyploidization and control the transition from endomitosis by inhibiting DNA synthesis and promoting apoptosis. Here, we test this hypothesis by examining the differential effect of mouse thrombopoietin (rmTpo) on the ploidy of p53−/− and p53+/+ mouse Mk cells. METHODS. 8–10 week-old, male p53−/− mice and p53+/+ littermates were injected once with 1.2 μg rmTpo or saline. On days 2 and 5 after Tpo/saline treatment, tail-bleeding assays were performed to measure bleeding times/volumes, mice were bled for platelet counts and sacrificed to harvest BM. We employed flow cytometry to examine baseline ploidy in BM-resident Mks in p53−/− and p53+/+ mice as well as Mk cells generated from BM progenitors after 4 and 6 days of culture with rmTpo. RESULTS. At steady state, ploidy in BM-resident CD41+ Mk cells was similar in p53−/− and p53+/+ mice: 11.8±2.3% and 10.7±1.3% of p53−/− and p53+/+ Mks, respectively, reaching a ploidy of ≥32N (n=3-4). Platelet counts were 1.3×106±1×105/μl (12.5±1.0% reticulated) and 1.1×106±5×104/μl (12.4±1.3% reticulated) in p53−/− and p53+/+ mice, respectively (n=8). Two days following Tpo treatment of the mice, we did not observe significantly increased platelet levels, while ploidy was marginally affected. However, 5 days following Tpo treatment, we found greater ploidy in the BM in the absence of p53: 22±1.6% 16N and 10.1±0.8% ≥32N Mks in the p53−/− versus 18.6±3.3% 16N and 7.1±1.4% ≥32N Mks in the p53+/+ (n=2). This was accompanied by increased platelet formation: 23.6±8.3% reticulated platelets in the p53−/− versus 17.8±2.6% in the p53+/+ (n=2). Culture of BM cells from non-Tpo treated mice with 50ng/ml rmTpo resulted in a 50% increase in total Mks and increased polyploidy by day 6 of culture: 38.6±4.6% of p53−/− versus 19.2±2.3% of p53+/+ Mks reached ploidy classes of ≥32N (n=3-4, p < 0.01). Lack of p53 led to hyperploid Mk cells; by day 6 of culture 10.3±2.2% of p53−/− Mks were in ploidy classes of 128N and higher, while only 0.6±0.1% p53+/+ Mks achieved such high ploidy (n=3-4). In addition, a 6 day culture with Tpo of BM cells derived from p53−/− and p53+/+ mice pre-treated with Tpo 5 days prior to sacrifice led to more profound polyploidization compared to Mks generated from the non-Tpo treated mice but only in the p53−/− Mks: 48.8±1.1% of p53−/− versus only 17.6±0.2% of p53+/+ Mks reached ploidy ≥32N (n=2). Microarray analysis comparing p53KD to control CHRF cells undergoing Mk differentiation revealed down-regulation of genes coding for platelet surface complex CD41/CD61 and CD62P in the p53KD cells. To examine the possibility of altered functionality of platelets in p53−/− mice, we performed tail-bleeding assays on the mice that did not receive Tpo. Bleeding times and volumes were generally prolonged in the absence of p53 (all p53−/− mice exceeded the 10 min duration of the assay; mean p53−/− and p53+/+ blood loss was 17μl and 10μl, respectively, n=3-4). CONCLUSIONS. Our data indicate that in vivo polyploidization and platelet formation from Mks is increased in the p53−/− relative to p53+/+ mice after Tpo administration. These data are in line with our hypothesis that p53 activation decreases the ability of Mks to respond to Tpo and undergo polyploidization. Additionally, our preliminary data on platelet functionality suggest that p53 may have a role in hemostasis. Disclosures: No relevant conflicts of interest to declare.

The Bone Marrow Niche of Patients with Acute Lymphoblastic Leukemia Produces No Increased Asparagine Levels In Vivo That May Lead to Clinical Asparaginase Resistance

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1505-1505
Author(s):  
Wing H. Tong ◽  
Rob Pieters ◽  
Wim C.J. Hop ◽  
Claudia Lanvers-Kaminsky ◽  
Joachim Boos ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Aspartic Acid ◽  
Peripheral Blood ◽  
Lymphoblastic Leukemia ◽  
Mesenchymal Cells ◽  
Leukemic Cells ◽  
Significant Difference ◽  
Trough Levels

Abstract Abstract 1505 Asparaginase is an essential component of combination chemotherapy of acute lymphoblastic leukemia (ALL). Asparaginase breaks down asparagine into aspartic acid and ammonia. Because asparagine is necessary for protein synthesis, its depletion leads to cell death. Recently, it has been suggested that mesenchymal cells in the bone marrow may produce asparagine and form ‘protective niches’ for leukemic cells. In vitro, this led to high levels of asparagine and asparaginase resistance of the ALL cells (Iwamoto et al. (J Clin Invest. 2007)). However, it is unknown if this holds true for the clinical in vivo situation. The aim of our study is to analyse whether mesenchymal cells or other cells in the bone marrow indeed produce significant amounts of asparagine in vivo that may lead to clinical asparaginase resistance. Ten de novo ALL patients were enrolled in this study. All children received induction chemotherapy according to protocol 1-A and 1-B of the Dutch Childhood Oncology Group (DCOG) ALL-10 protocol. Asparaginase levels and amino acid levels (asparagine, aspartic acid, glutamine and glutamic acid) were measured in bone marrow (BM) and peripheral blood at diagnosis (day 1), days 15, 33 and 79. On days that asparaginase was administered (days 15 and 33) it was ensured that study material was obtained before the E-coli L-asparaginase infusions. Changes over time of asparaginase trough levels in BM and peripheral blood were evaluated using Mixed models ANOVA. The amino acids levels in 0.5 ml BM, 3 ml BM and peripheral blood at days 15 and 33 were also compared using Mixed models ANOVA. All these analyses were done after log transformation of measured values to get approximate normal distributions. A two-sided p-value < 0.05 was considered statistically significant. The asparaginase levels were all below detection limit (< 5 IU/L) in BM and peripheral blood at days 1 and 79. In both compartments, the median asparaginase trough levels were not significantly different at days 15 and 33. At diagnosis, no significant difference in asparagine level between 3 ml BM and peripheral blood was found (median: 44.5 μM (range 20.6–59.6 μM) and 43.9 μM (range 18.4 –58.5 μM), respectively). However, the median level of aspartic acid at diagnosis in 3 ml BM (19.2 μM; range 6.2–52.6 μM) was significantly higher as compared to median level of peripheral blood (5.7 μM; range 2.4–10.1 μM) (p=0.002). The aspartic acid levels were also higher in BM compared to peripheral blood at days 15 and 33 (both p=0.001) and at day 79 (p=0.002). Aspartic acid levels were significantly higher in 0.5 ml versus 3 ml BM (p=0.001) and this difference was also found when comparing 0.5 ml BM versus peripheral blood (p<0.001) suggesting dilution with peripheral blood when taking higher volumes of ‘bone marrow’. Asparagine levels were all below the lower limit of quantification (LLQ < 0.2 μM) in both BM and blood during asparaginase treatment at days 15 and 33. At day 79, no significant difference in asparagine levels between BM (37.7 μM; range 33.4–50.3 μM) and peripheral blood (38.9 μM; range 25.7 –51.3 μM) was seen. During the time course of asparaginase infusions, the glutamine and glutamic acid levels did not change significantly. In conclusion, we demonstrate higher aspartic acid levels in bone marrow compared to peripheral blood. The higher aspartic acid levels are detected at diagnosis, during asparaginase therapy at days 15 and 33, and also at day 79 at complete remission, showing that these do not originate from leukemic cells nor from asparagine breakdown by asparaginase but from cells in the microenvironment of the bone marrow. However, there is no increased asparagine synthesis in vivo in the bone marrow of ALL patients. Therefore, increased asparagine synthesis by mesenchymal cells may be of relevance for resistance to asparaginase of leukemic cells in vitro but not in vivo. Disclosures: No relevant conflicts of interest to declare.

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