Intersecting High-Throughput Screens Identifies SERCA As a Target for Modulating NOTCH1 In Hematopoietic Malignancies

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 555-555
Author(s):  
Giovanni Roti ◽  
Annie Carlton ◽  
Kenneth N. Ross ◽  
Michele Markstein ◽  
Kostandin Pajcini ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endoplasmic Reticulum ◽  
Stem Cell ◽  
Cell Lines ◽  
High Throughput ◽  
Lymphoblastic Leukemia ◽  
Cyclopiazonic Acid ◽  
Luciferase Reporter ◽  
Gamma Secretase ◽  
High Throughput Screens

Abstract Abstract 555 While long-term survival rates for children with acute lymphoblastic leukemia (ALL) are approximately 80%, we have reached a plateau over the past decade with combination chemotherapy. ALL remains a leading cause of cancer-related death in children, and even for those children cured, morbidity is significant. Moreover, prognosis for adults with ALL is poor. Alternative approaches to treating this disease are needed. NOTCH1 is a well-validated target in hematopoietic malignancy, with NOTCH1 activating mutations identified in over 50% of T-cell acute lymphoblastic leukemia (T-ALL) and in 12% of chronic lymphocytic leukemias. NOTCH1 is a heterodimeric protein, normally activated by a series of proteolytic cleavages upon ligand stimulation, which forms a transcription factor complex altering gene expression. We intersected the results of two high-throughput screens focused on modulating NOTCH1 to identify new NOTCH1 inhibitors. First, we applied an unbiased, cell-based gene expression signature screening approach to identify new NOTCH1 inhibitors (Gene Expression-based High-throughput Screening (GE-HTS)) in which a gene signature serves as a surrogate for inactive NOTCH1. Among top-scoring compounds inducing the NOTCH1 inactivation signature, we identified inhibitors of SERCA (Sarco/endoplasmic Reticulum Ca++ATPase) channels, such as the natural products thapsigargin and cyclopiazonic acid. We integrated these results with a cDNA library screen for NOTCH1 activation in which U2OS cells expressing a leukemic NOTCH1 allele, L1601PδP, were scored for NOTCH1-sensitive RBPJ luciferase reporter activity. This screen also identified the SERCA genes ATP2A2 and ATP2A3 as top candidates, whose expression activates NOTCH1, complementing our original observation of SERCA inhibition as an approach to inhibit NOTCH1. SERCA proteins reside on the endoplasmic reticulum and are responsible for the transfer of calcium from the cytosol of the cell to the lumen of the endoplasmic reticulum. We focused our attention on the more potent molecule, thapsigargin, and confirmed that it induces the NOTCH1 off signatures across multiple T-ALL cell lines and targets NOTCH1 signaling by demonstrating its inhibitory effects on the RBPJ luciferase reporter in heterologous U2OS cells expressing the L1601PδP mutation. The anti-leukemic phenotype induced by thapsigargin was consistent with that previously reported with inhibition of gamma secretase, the enzyme involved in the final activation step of NOTCH1. Decreased viability and cell size and a G1/G0 arrest were observed upon low nanomolar thapsigargin treatment in multiple T-ALL cell lines. These effects were on-target for NOTCH1 inhibition. Overexpression of the activated form of NOTCH1, (ICN1) restored the expression of the NOTCH1 target genes c-MYC and DTX1 upon thapsigargin treatment and rescued the effects of thapsigargin on T-ALL viability. As in gamma secretase inhibitor (GSI) treatment, we observed that thapsigargin altered the level of active ICN1 protein in T-ALL cell lines. However, in contrast to treatment with GSI, thapsigargin also decreased levels of the furin-processed transmembrane forms of NOTCH1, while the full length NOTCH1 precursor accumulated as demonstrated by western blot and immunofluorescence studies. To further confirm the role of SERCA activity in NOTCH1 maturation, we inhibited Ca++ATPase activity with SERCA-directed shRNA in T-ALL cell lines and demonstrated that genetically-driven inhibition of ATP2A2 results in loss of ICN1 and trans-membrane NOTCH1 and the expected phenotypic consequences: reduced viability and G1/G0 arrest. To confirm that both chemical and genetic inhibition of SERCA leads to NOTCH inactivation in vivo, we adopted a Drosophila intestinal cancer stem cell model in which the inhibition of NOTCH1 prevents differentiation of stem cell daughter cells resulting in an expansion of the stem cell population. Treating Drosophila with thapsigargin or cyclopiazonic acid resulted in an expansion of the stem cell pool consistent with NOTCH inhibition. Indeed, a transgenic RNAi hairpin directed against Ca-P60A (the Drosophila SERCA orthologue) recapitulated the NOTCH phenotype observed with chemical treatment. In summary, these pre-clinical studies suggest a role for SERCA modulation of NOTCH1 maturation and identify SERCA as a potentially druggable target to inhibit NOTCH1 in T-ALL. Disclosures: No relevant conflicts of interest to declare.

PLAG1 and USF2 Regulate Primitive Hematopoietic Expression of Musashi-2

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3583-3583
Author(s):  
Muluken S Belew ◽  
Stefan Rentas ◽  
Laura de Rooij ◽  
Kristin J Hope
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Cell Lines ◽  
Regulatory Elements ◽  
Hematopoietic Cell ◽  
Minimal Promoter ◽  
Luciferase Reporter ◽  
Specific Expression ◽  
Self Renewal ◽  
Model Cell

Abstract The Musashi-2 (MSI2) RNA binding protein is now recognized as a key regulator of hematopoietic stem cells (HSCs). Its expression is most elevated in the primitive HSC compartment and progressively decreases with differentiation. In mouse models of CML, ectopic expression of MSI2 drives progression from the chronic to the blast crisis state while in the human context its aberrantly high expression correlates with more aggressive CML disease states and is associated with poor prognosis in AML. These studies suggest that the precise molecular regulation of MSI2 gene expression may be among the critical mechanisms underlying balanced HSC self-renewal and differentiation and as a result, the prevention of leukemic transformation/progression. Despite the clear importance of understanding how Msi2 maintains an appropriate stem cell-specific expression level, very little is understood of the transcription factors (TFs) that mediate this. To define those factors that govern MSI2 expression and function specifically in the HSC compartment we undertook a systematic approach to map and define relevant regulatory elements of the MSI2 minimal promoter. We dissected a 3.5 kb region 5' upstream of MSI2's translational start site (TSS) shared between mouse and human and thus having the greatest potential of containing regulatory elements key to a conserved MSI2 stem-cell-specific gene expression program. Progressive 5'-terminal deletions of this region cloned upstream of a luciferase reporter gene and transfected into K562 and 293T model cell lines allowed us to define a minimal conserved promoter region from -588 to -203 bp upstream of the TSS that reports accurately on endogenous MSI2 expression. Coupled with in silico prediction of TF that bind this region, systematic TF binding site mutagenesis and luciferase reporter assays in model cell lines identified USF2 and PLAG1 as TFs whose direct binding to the MSI2 minimal promoter direct reporter activity. Loss and gain of function studies in K562 cells confirm that these factors co-regulate the transactivation of endogenous MSI2. Moreover we show in the most relevant primary human CD34+ hematopoietic cell context that these factors bind the MSI2 minimal promoter. While USF2 is a ubiquitously expressed TF across the hematopoietic hierarchy, the uniquely restricted expression of PLAG1 within only the most primitive of hematopoietic cells suggests that it specifically contributes to the heightened stem cell-specific expression of MSI2. Consistent with its role as a key driver of MSI2 and thus an enforcer of its pro-self-renewal functions, we found that overexpression of PLAG1 in human Lin-CD34+ cord blood cells enhanced MSI2 transcription and increased total Colony Forming Unit (CFU) output and re-plating efficiency of primitive CFU progenitors. PLAG1 overexpression also offered a pro-survival advantage to these cells as evidenced by a more than two-fold reduction in Annexin V positive cells compared to negative controls. We have thus described important transcriptional circuitry that governs stem-cell specific expression of MSI2 while at the same time functionally validated PLAG1 as a novel factor capable of modulating primitive hematopoietic cell self-renewal and survival. Disclosures No relevant conflicts of interest to declare.

scholarly journals Development of a Cell-Based Reporter Assay for Screening of Inhibitors of Hypoxia-Inducible Factor 2-Induced Gene Expression

2006 ◽  
Vol 11 (6) ◽  
pp. 678-687 ◽  
Author(s):  
Girma M. Woldemichael ◽  
James R. Vasselli ◽  
Roberta S. Gardella ◽  
Tawnya C. Mckee ◽  
W. Marston Linehan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Lines ◽  
High Throughput ◽  
High Throughput Screening ◽  
Dynamic Range ◽  
Clear Cell ◽  
Hypoxia Inducible Factor ◽  
Luciferase Reporter ◽  
Reporter Cell

Reporter cell lines have been developed for the identification of inhibitors of gene expression enhanced by hypoxia-inducible factor 2, which has been implicated as a transcription factor involved in the tumorigenesis of clear cell renal carcinoma. Stably transformed reporter clones of the human renal clear cell carcinoma cell line 786-O were generated by transfection or retroviral infection. Luciferase reporter expression in the vectors used was driven by either the natural human vascular endothelial growth factor (VEGF) promoter-enhancer or by the VEGF and the human endothelial nitric oxide synthase enhancers modulating minimal human cytomegalovirus promoter. Utility of the generated reporter cell lines was validated by introducing the von Hippel-Lindau protein complex and testing for reporter inducibility by hypoxia. The dynamic range in reporter activity under hypoxic stress was found to be at least 30- to 40-fold, with a signal-to-noise ratio of 60:1. Properties of the cell lines such as tolerance to up to 3% DMSO, signal stability with multiple in vitro passages, and utility in both 96- and 384-well plate formats indicated their suitability for use in a high-throughput screen. In addition, the potential use of these reporter lines in the evaluation of high-throughput screening hits in vivo in various mice models has been demonstrated.

Expression-Based Screen Identifies the Calcium Channel Antagonist Bepridil as a Notch1 Modulator in T-ALL.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 366-366 ◽  
Author(s):  
Giovanni Roti ◽  
Kenneth N. Ross ◽  
Adolfo A. Ferrando ◽  
Stephen C Blacklow ◽  
Jon Aster ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Calcium Channel ◽  
Cell Line ◽  
Cell Lines ◽  
Small Molecule ◽  
Lymphoblastic Leukemia ◽  
Receptor Activation ◽  
Luciferase Reporter ◽  
Small Molecule Library

Abstract Abstract 366 Gain of function mutations in Notch1, which encodes a signaling protein that is converted into a transcription factor upon activation, are the most common genetic abnormality in human T-cell acute lymphoblastic leukemia (T-ALL). Although inhibiting Notch1 activity represents a potential therapeutic opportunity, the discovery of new Notch1 pathway antagonists poses a difficult challenge. Traditional small molecule library screening approaches have not been amenable to modulating transcription factor abnormalities. In order to overcome this challenge, we applied Gene Expression-based High-throughput Screening (GE-HTS) to discover new Notch1 modulators. GE-HTS uses gene expression signatures as surrogates for different biological states. We derived a 32-gene Notch1 expression signature from genome-wide microarray expression profiling of 7 different Notch1 mutant T-ALL cell lines treated with vehicle (Notch1 on) versus a Notch1 inactivating γ-secretase inhibitor (GSI; Notch off) and screened a small molecule library for compounds inducing the Notch1 off state in DND41 mutant Notch1 T-ALL cells. Among numerous ion flux modulators validated to induce the Notch1 off signature, one of the top hits was the FDA-approved calcium channel blocker, bepridil, used to treat patients with cardiac disease. In multiple mutant Notch1 T-ALL cell lines, bepridil induced the Notch1 off signature. We next confirmed that bepridil indeed targets Notch signaling by demonstrating its inhibitory effects on a Notch-sensitive luciferase reporter gene in heterologous U2OS cells expressing a mutated form of Notch1. Similar to the phenotypic effects of GSI, bepridil induced a G0/G1 cell cycle arrest, inhibited cellular viability, and decreased cell size in multiple T-ALL cell lines, including the GSI-resistant cell line PF382. Next, in order to confirm dependency of the induced phenotype on inhibition of Notch, we utilized the 8946 T-ALL cell line. This murine line depends on a doxycycline-repressible human c-myc transgene for growth and can be rescued from transgene withdrawal with activated Notch1, which upregulates the endogenous c-myc gene. In these cells, the phenotypic effect of bepridil on viability is also dependent on Notch1 inhibition because cells rescued from transgene withdrawal with activated Notch1 were more sensitive to the effects of the drug than were those cells still dependent on the c-myc transgene. Finally, we asked whether bepridil altered the level of active Notch1 protein in T-ALL cell lines. As with GSI, bepridil treatment results in decreased levels of intracellular Notch (ICN1). In contrast to GSI, however, bepridil treatment decreased levels of the furin-processed extracellular and transmembrane forms of Notch1 while the full length Notch1 precursor form accumulated upon bepridil treatment. One hypothesis is that by altering ER/Golgi compartment calcium, bepridil prevents the folding of newly synthesized Notch1 polypeptides, leading to its retention in the ER/Golgi and a failure to traffic to cellular compartments where receptor activation occurs. Consistent with this hypothesis co-localization studies in U2OS cell lines expressing the L1601P mutant Notch1 suggest retention of Notch1 in the ER/Golgi. An alternative hypothesis under investigation is that bepridil affects the activity of furin, a calcium-dependent protease that is required for processing of Notch receptors. In summary, we have identified an FDA-approved drug with Notch1 modulating activity in T-ALL by a mechanism unique from GSI. These studies have potential for rapid translation to clinical testing. Disclosures: Ferrando: Merck, Pfizer: Research Funding.

scholarly journals Comparative activity of pulsed or continuous estradiol exposure on gene expression and proliferation of normal and tumoral human breast cells

2002 ◽  
Vol 28 (3) ◽  
pp. 165-175 ◽  
Author(s):  
V Cavailles ◽  
A Gompel ◽  
MC Portois ◽  
S Thenot ◽  
N Mabon ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Lines ◽  
Hormone Replacement ◽  
Primary Cultures ◽  
Continuous Treatment ◽  
Luciferase Reporter ◽  
Breast Cancer Cell Lines ◽  
Human Breast ◽  
Kinetic Profile ◽  
Breast Cells

Intranasal administration of hormone replacement therapy presents an original plasma kinetic profile with transient estrogen levels giving rise to the concept of pulsed therapy. To further understand the molecular effects of this new therapy, we have compared the effects of pulsed and continuous estradiol treatments on two critical aspects of estradiol action: gene expression and cell proliferation. Cells were stimulated with estradiol as 1-h pulsed or 24-h continuous treatments at concentrations such that the 24-h exposure (concentration x time) was identical in both conditions. In MCF7 cells, the transcriptional activity of estrogen receptors (ER) on a transiently transfected responsive estrogen response element-luciferase reporter construct was shown to be drastically (approximately 10-fold) and similarly stimulated after both treatments. Moreover, the increased mRNA expression of three representative estradiol-sensitive genes (pS2, cathepsin D, progesterone receptor), evaluated by Northern blot, was identical after 1-h pulse with 7 nM estradiol or continuous treatment with 0.29 nM estradiol with the same kinetic profile over 48 h. Proliferation was quantified by a histomorphometric method on primary cultures of human normal breast cells from reduction mammoplasties and using a fluorescence DNA assay in six human breast cancer cell lines which were ER positive or negative. After a 7-day treatment period, estradiol had no effect on the proliferation of the three ER negative cell lines (BT20, MDA MB231, SK BR3) but significantly stimulated the proliferation of the normal cells and of the three tumoral hormone-sensitive cell lines (MCF7, T47D, ZR 75-1); both hormone treatments producing the same increases in cell growth. In conclusion, we have shown that the genomic or proliferative effects of estradiol were identical with pulsed or continuous treatments, thus indicating that estrogenic effects are not strictly related to concentrations but rather to total hormone exposure.

scholarly journals Targeted gene transfer to human hematopoietic progenitor cell lines through the c-kit receptor

Blood ◽  
1996 ◽  
Vol 87 (2) ◽  
pp. 472-478 ◽  
Author(s):  
P Schwarzenberger ◽  
SE Spence ◽  
JM Gooya ◽  
D Michiel ◽  
DT Curiel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Progenitor Cells ◽  
Cell Lines ◽  
Progenitor Cell ◽  
Gene Transfection ◽  
Luciferase Reporter ◽  
Hematopoietic Progenitor Cell ◽  
Hematopoietic Progenitor ◽  
Hematopoietic Stem ◽  
Covalently Linked

In this report, we describe a novel gene therapy approach for hematopoietic stem/progenitor cells using a specific receptor-mediated gene transfection procedure to target c-kit+ cell lines. The vector consists of plasmid DNA containing a luciferase reporter gene that is condensed by electrostatic forces with polylysine (PL) covalently linked to streptavidin (binds biotinylated ligand) and PL covalently linked to adenovirus (AD; to achieve endosomal lysis) with the final addition of biotinylated steel factor (SLF-biotin). Targeted transfection of growth factor-dependent hematopoietic progenitor cell lines that express c-kit showed specific luciferase gene expression over cell lines that did not express c-kit. This effect was dependent on the dose of SLF-biotin and was competed by excess SLF or with monoclonal antibodies that recognize c-kit and block the binding of SLF to its receptor. Maximum transfection efficiency (> 90%) requires a 2- hour incubation period of the vector with the cells, and maximum gene expression occurred 30 hours later. Removal of the endosomalytic agent, AD, from the vector resulted in the loss of gene expression. Vector targeting was versatile and could be changed by the addition of other biotinylated ligands. In principle, this vector should be broadly applicable to deliver genes to hematopoietic stem/progenitor cells in vitro and in vivo.

WT1-Specific CD8+ T Lymphocytes May Participate in the Elimination of Acute Lymphoblastic Leukemia Following Allogeneic Stem Cell Transplantation.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3679-3679 ◽  
Author(s):  
Katayoun Rezvani ◽  
Agnes Yong ◽  
Stephan Mielke ◽  
Bipin N. Savani ◽  
David A. Price ◽  
...  
Keyword(s):  
Gene Expression ◽  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Cd8 T Cells ◽  
Lymphoblastic Leukemia ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
Wt1 Gene ◽  
Cell Responses

Abstract There is clinical evidence that a graft-versus-leukemia (GVL) effect occurs following allogeneic stem cell transplantation for acute lymphoblastic leukemia (ALL). However, the potency of this GVL effect is often associated with unwanted graft-versus-host-disease (GVHD) and disease relapse remains a major contributor to treatment failure. Wilms’ tumor gene 1 (WT1) is overexpressed in 70–90% of cases of ALL and has been identified as a convenient minimal residual disease (MRD) marker. WT1 is an attractive immunotherapeutic target in ALL because peptides derived from WT1 can induce CD8+ T-cell responses, and being non-allelic, WT1 would be unlikely to provoke GVHD. We investigated whether CD8+ T-cells directed against an HLA-A*0201 restricted epitope of WT1 (WT126) occur in ALL patients during the early phase of immune reconstitution post-SCT (days 30–180). We analyzed CD8+ T-cell responses against WT1 in 10 HLA-A*0201+ ALL SCT recipients and their respective donors using WT1/HLA-A*0201 tetrameric complexes and flow cytometry for intracellular IFN-gamma. We studied the kinetics WT1-specific CD8+ T-cell responses in consecutive samples obtained post-SCT. CD8+ T-cells recognizing WT1 were detected ex vivo in samples from 5 of 10 ALL patients post-SCT but not in patients pre-SCT. WT1-tetramer+ CD8+ T cells had a predominantly effector memory phenotype (CD45RO+CD27−CD57+). WT1 gene expression in pre-SCT and donor samples was assayed by quantitative real-time PCR (RQ-PCR). WT1 expression in PBMC from healthy donors was significantly lower than in patients (median 0, range 0–66 ×10−4 WT1/ABL compared to patients, median 12, range 0–2275 ×10−4 WT1/ABL) (P < 0.01). There was a strong correlation between the emergence of WT1-specific CD8+ T cells and a reduction in WT1 gene expression (P < 0.001) (as depicted below) suggesting direct anti-ALL activity post-SCT. Disappearance of WT1-specific CD8+ T-cells from the blood coincided with reappearance of WT1 gene transcripts, consistent with a molecular relapse, further supporting the direct involvement of WT1-specific CD8+ T-cells in the GVL response. These results provide evidence for the first time of spontaneous T-cell reactivity against a leukemia antigen in ALL patients. Our results support the immunogenicity of WT1 in ALL patients post-SCT and a potential application for WT1 peptides in post-transplant immunotherapy of ALL. Figure Figure

Early T-Cell Precursor-ALL in Adult T-ALL.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 911-911 ◽  
Author(s):  
Martin Neumann ◽  
Sandra Heesch ◽  
Stefan Schwartz ◽  
Nicola Gökbuget ◽  
Dieter Hoelzer ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Real Time ◽  
Gene Expression Profile ◽  
Expression Profile ◽  
Real Time Pcr ◽  
Expression Profiles ◽  
Lymphoblastic Leukemia ◽  
Gene Expression Profiles ◽  
Study Group

Abstract Abstract 911 Introduction: Recently, a small subgroup of pediatric acute T-lymphoblastic leukemia (T-ALL) was described, which is closely associated with the gene expression profile of early T-cell precursors (ETPs). This subtype, termed ETP-ALL, showed a highly unfavorable outcome compared to non-ETP(='typical')-ALL. Based on the results of Coustan-Smith et al. (Lancet Oncology, 2009), the Italian national study Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) and St-Jude Children's hospital modified their treatment in children with ETP-ALL to a more intensive regime including stem cell transplantation. ETP-ALL is characterized by a specific immunophenotype (CD1a-, CD8-, CD5weak with expression of stem cell or myeloid markers). Here we explored the existence of ETP-ALL in adults and further studied the molecular characteristics of this specific T-ALL subtype. Patients and methods: We examined the gene expression profiles of 86 adult T-ALL patients obtained from the Microarray Innovations in LEukemia (MILE) multicenter study (HG-U133 Plus 2.0, Affymetrix, Haferlach et al., JCO in press). In addition, bone marrow of 296 patients from the German Acute Lymphoblastic Leukemia Multicenter Study Group (GMALL) were analyzed by flow cytometry and expression levels of BAALC, IGFBP7, MN1, and WT1 were determined by real-time-PCR. Results: Using the published list of differentially expressed genes in ETPs (Coustan-Smith et al. 2009) we performed unsupervised clustering analyses of the 86 T-ALL samples. A cluster of 17 samples (19.8%) displayed an ETP-associated gene expression profile and were defined as ETP-ALL. Comparing the gene expression profiles of ETP-ALL and typical T-ALL, 2065 probe sets were differentially expressed in ETP-ALL (FDR 0.05). In addition to genes used for classification, we also identified genes known to be involved in the pathogenesis of T-ALL (e.g. PROM1, BCL2, LMO2, LYL1). In particular, stem cell associated genes such as, BAALC (2.52-fold, p=0.003), IGFBP7 (2.76-fold, p=0.002) or MN1 (3.41-fold, p<0.001) were upregulated in ETP-ALL, whereas HOX11 (45-fold, p=0.004), a marker for thymic T-ALL, was downregulated. An independent cohort of 297 patient samples from the GMALL study group was examined by flow cytometry and real-time PCR. 19 (6.4%) samples revealed the ETP-ALL immunophenotype. As expected, all patient samples were found in the group of early T-ALL, representing 23.5% of all early T-ALLs. There was a significant correlation between a lower leukocyte count at first diagnosis and the classification of ETP-ALL (p=0.001). Gene expression measured by real-time-PCR was performed for genes associated with poor outcome in T-ALL: BAALC (2.11-fold, p<0.001) and IGFBP7 (3.59-fold, p=0.003) were significantly upregulated in the group of ETP-ALL. Similarly, the genes MN1 (4.52-fold, p<0.001) and WT1 (2.76-fold, p=0.036), described as poor prognostic markers in cytogenetically normal AML, were also upregulated in ETP-ALL. Conclusion: In adult T-ALL, a subset of patients shares the gene expression profil and immunophenotype of ETP-ALL, which is in line with recent findings in pediatric patients. The gene expression profile of this subset is significantly correlated to stem cell associated markers predictive for inferior outcome in T-ALL. Interestingly, adverse factors in CN-AML are also aberrantly expressed in ETP-ALL suggesting a myeloid origin of ETPs and indicating a closer relationship between ETP-ALL and AML. The prognostic impact and the determination of the most appropiate set of markers needs to be further investigated. These results support the GMALL strategy to regard early T-ALL patients as high risk with assignment to stem cell transplantation. Disclosures: Haferlach: MLL Munich Leukemia Laboratory: Equity Ownership.

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