scholarly journals A Novel, Myeloid Transcription Factor, C/EBPε, Is Upregulated During Granulocytic, But Not Monocytic, Differentiation

Blood ◽  
1997 ◽  
Vol 90 (7) ◽  
pp. 2591-2600 ◽  
Author(s):  
Roberta Morosetti ◽  
Dorothy J. Park ◽  
Alexey M. Chumakov ◽  
Isabelle Grillier ◽  
Masaaki Shiohara ◽  
...  
Keyword(s):  
Stem Cells ◽  
Transcription Factor ◽  
Hematopoietic Stem Cells ◽  
Cell Line ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Rt Pcr ◽  
Hematopoietic Stem ◽  
Nb4 Cells

Human C/EBPε is a newly cloned CCAAT/enhancer-binding transcription factor. Initial studies indicated it may be an important regulator of human myelopoiesis. To elucidate the range of expression of C/EBPε, we used reverse transcription-polymerase chain reaction (RT-PCR) analysis and examined its expression in 28 hematopoietic and 14 nonhematopoietic cell lines, 16 fresh myeloid leukemia samples, and normal human hematopoietic stem cells and their mature progeny. Prominent expression of C/EBPε mRNA occurred in the late myeloblastic and promyelocytic cell lines (NB4, HL60, GFD8), the myelomonoblastic cell lines (U937 and THP-1), the early myeloblast cell lines (ML1, KCL22, MDS92), and the T-cell lymphoblastic leukemia cell lines CEM and HSB-2. For the acute promyelocytic leukemia cell line NB4, C/EBPε was the only C/EBP family member that was easily detected by RT-PCR. No C/EBPε mRNA was found in erythroid, megakaryocyte, basophil, B lymphoid, or nonhematopoietic cell lines. Most acute myeloid leukemia samples (11 of 12) from patients expressed C/EBPε. Northern blot and RT-PCR analyses showed that C/EBPε mRNA decreased when the HL60 and KG-1 myeloblast cell lines were induced to differentiate toward macrophages. Similarly, Western blot analysis showed that expression of C/EBPε protein was either unchanged or decreased slightly as the promyelocytic cell line NB4 differentiated down the macrophage-like pathway after treatment with a potent vitamin D3 analog (KH1060). In contrast, C/EBPε protein levels increased dramatically as NB4 cells were induced to differentiate down the granulocytic pathway after exposure to 9-cis retinoic acid. Furthermore, very early, normal hematopoietic stem cells (CD34+/CD38−), purified from humans had very weak expression of C/EBPε mRNA, but levels increased as these cells differentiated towards granulocytes. Likewise, purified granulocytes appeared to express higher levels of C/EBPε mRNA than purified macrophages. Addition of phosphothiolated antisense, but not sense oligonucleotides to C/EBPε, decreased clonal growth of HL-60 and NB4 cells by about 50% compared with control cultures. Taken together, our results indicate that expression of C/EBPε is restricted to hematopoietic tissues, especially myeloid cells as they differentiate towards granulocytes and inhibition of its expression in HL-60 and NB4 myeloblasts and promyelocytes decreased their proliferative capacity. Therefore, this transcriptional factor may play an important role in the process of normal myeloid development.

scholarly journals A Novel, Myeloid Transcription Factor, C/EBPε, Is Upregulated During Granulocytic, But Not Monocytic, Differentiation

Blood ◽  
1997 ◽  
Vol 90 (7) ◽  
pp. 2591-2600 ◽  
Author(s):  
Roberta Morosetti ◽  
Dorothy J. Park ◽  
Alexey M. Chumakov ◽  
Isabelle Grillier ◽  
Masaaki Shiohara ◽  
...  
Keyword(s):  
Stem Cells ◽  
Transcription Factor ◽  
Hematopoietic Stem Cells ◽  
Cell Line ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Rt Pcr ◽  
Hematopoietic Stem ◽  
Nb4 Cells

Abstract Human C/EBPε is a newly cloned CCAAT/enhancer-binding transcription factor. Initial studies indicated it may be an important regulator of human myelopoiesis. To elucidate the range of expression of C/EBPε, we used reverse transcription-polymerase chain reaction (RT-PCR) analysis and examined its expression in 28 hematopoietic and 14 nonhematopoietic cell lines, 16 fresh myeloid leukemia samples, and normal human hematopoietic stem cells and their mature progeny. Prominent expression of C/EBPε mRNA occurred in the late myeloblastic and promyelocytic cell lines (NB4, HL60, GFD8), the myelomonoblastic cell lines (U937 and THP-1), the early myeloblast cell lines (ML1, KCL22, MDS92), and the T-cell lymphoblastic leukemia cell lines CEM and HSB-2. For the acute promyelocytic leukemia cell line NB4, C/EBPε was the only C/EBP family member that was easily detected by RT-PCR. No C/EBPε mRNA was found in erythroid, megakaryocyte, basophil, B lymphoid, or nonhematopoietic cell lines. Most acute myeloid leukemia samples (11 of 12) from patients expressed C/EBPε. Northern blot and RT-PCR analyses showed that C/EBPε mRNA decreased when the HL60 and KG-1 myeloblast cell lines were induced to differentiate toward macrophages. Similarly, Western blot analysis showed that expression of C/EBPε protein was either unchanged or decreased slightly as the promyelocytic cell line NB4 differentiated down the macrophage-like pathway after treatment with a potent vitamin D3 analog (KH1060). In contrast, C/EBPε protein levels increased dramatically as NB4 cells were induced to differentiate down the granulocytic pathway after exposure to 9-cis retinoic acid. Furthermore, very early, normal hematopoietic stem cells (CD34+/CD38−), purified from humans had very weak expression of C/EBPε mRNA, but levels increased as these cells differentiated towards granulocytes. Likewise, purified granulocytes appeared to express higher levels of C/EBPε mRNA than purified macrophages. Addition of phosphothiolated antisense, but not sense oligonucleotides to C/EBPε, decreased clonal growth of HL-60 and NB4 cells by about 50% compared with control cultures. Taken together, our results indicate that expression of C/EBPε is restricted to hematopoietic tissues, especially myeloid cells as they differentiate towards granulocytes and inhibition of its expression in HL-60 and NB4 myeloblasts and promyelocytes decreased their proliferative capacity. Therefore, this transcriptional factor may play an important role in the process of normal myeloid development.

TIM-3 Is a Promising Target to Eradicate Acute Myeloid Leukemia Stem Cells Sparing Normal Hematopoietic Stem Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 559-559
Author(s):  
Toshihiro Miyamoto ◽  
Yoshikane Kikushige ◽  
Takahiro Shima ◽  
Koichi Akashi
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Cytotoxic Activities ◽  
Antibody Treatment ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract Abstract 559 Acute myeloid leukemia (AML) originates from self-renewing leukemic stem cells (LSCs), an ultimate therapeutic target for permanent cure. To selectively kill AML LSCs sparing normal hematopoietic stem cells (HSCs), one of the most practical approaches is to target the AML LSCs-specific surface or functionally indispensable molecules. Based on differential transcriptome analysis of prospectively-purified CD34+CD38− LSCs from AML patient samples and normal HSCs, we found that T-cell immunoglobulin mucin-3 (TIM-3) was highly expressed in AML LSCs but not in normal HSCs (Kikushige et al., Cell Stem Cell, 2010). In normal hematopoiesis, TIM-3 is mainly expressed in mature monocytes and a fraction of NK cells, but not in granulocytes, T cells or B cells. In the bone marrow, TIM-3 is expressed only in a fraction of granulocyte/macrophage progenitors (GMPs) at a low level, but not in HSCs, common myeloid progenitors, or megakaryocyte/erythrocyte progenitors. In contrast, in human AML, TIM-3 was expressed on cell surface of the vast majority of CD34+CD38− LSCs and CD34+CD38+ leukemic progenitors in AML of most FAB types, except for acute promyelocytic leukemia (M3). FACS-sorted TIM-3+ but not TIM-3− AML cells reconstituted human AML in the immunodeficient mice, indicating that the TIM-3+ population contains most of functional LSCs. To selectively eradicate TIM-3-expressing AML LSCs, we established an anti-human TIM-3 mouse IgG2a antibody, ATIK2a, possessing antibody-dependent cellular cytotoxic and complement-dependent cytotoxic activities in leukemia cell lines transfected with TIM-3. We first tested the effect of ATIK2a treatment on reconstitution of normal HSCs in a xenograft model. ATIK2a was intraperitoneally injected to the mice once a week after 12 hours of transplantation of human CD34+ cells. Injection of ATIK2a did not affect reconstitution of normal human hematopoiesis except removing TIM-3-expressing mature monocytes. In contrast, injection of TIM-3 to the mice transplanted with human AML samples markedly reduced leukemic repopulation. In some mice transplanted with AML bone marrow, only normal hematopoiesis was reconstituted after anti-TIM-3 antibody treatment, suggesting that the antibody selectively killed AML cells, sparing residual normal HSCs. To further test the inhibitory effect of ATIK2a on established human AML, eight weeks after transplantation of human AML cells, engraftment of human AML cells was confirmed by blood sampling and thereafter ATIK2a was injected to these mice. In all cases tested, ATIK2a treatment significantly reduced human TIM-3+ AML fraction as well as the CD34+CD38− LSCs fraction. In addition, to verify the anti-AML LSCs effect of ATIK2a treatment, human CD45+AML cells from the primary recipients were re-transplanted into secondary recipients. All mice transplanted from primary recipients treated with control IgG developed AML, whereas none of mice transplanted with cells from ATIK2a-treated primary recipients developed AML, suggesting that functional LSCs were effectively eliminated by ATIK2a treatment in primary recipients. Thus, TIM-3 is a promising surface molecule to target AML LSCs. Our experiments strongly suggest that targeting this molecule by monoclonal antibody treatment is a practical approach to eradicate human AML. Disclosures: No relevant conflicts of interest to declare.

Expression and Functional Analysis of Autotaxin, a Relevant Motility and Survival Factor, in FLT3-ITD Positive Acute Myeloid Leukemia and Primary Hematopoietic Stem Cells.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1206-1206
Author(s):  
Claudia Ortlepp ◽  
Christine Steudel ◽  
Sina Koch ◽  
Angela Jacobi ◽  
Satu Kyttaelae ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemic Cell ◽  
Hematopoietic Stem ◽  
Human Leukemic Cell ◽  
Leukemic Cell Lines ◽  
Acute Myeloid

Abstract FLT3-mutations are among the most common abnormalities in adult acute myeloid leukemia. These mutations induce constitutive activation of the receptor and downstream signaling pathways, including RAS/ERK, PI3K and STAT5-signalling. The most frequent aberration is an internal tandem duplication (ITD) of the juxtamembrane domain coding sequence, which is present in up to 27% of the patients with AML and has been associated with inferior prognosis. We have recently demonstrated by microarray analysis that leukemic samples of patients with FLT3-ITD mutations have significantly upregulated expression levels of Autotaxin (ATX). The ATX protein acts as a secreted lysophospholipase D (lysoPLD) through generating lysophosphatidic acid (LPA) from lysophosphatidylcholine (LPC). LPA has several important functions in cell migration and proliferation and acts via G-protein coupled receptors. It has been shown that ATX represents an aberrantly expressed motility and growth factor in a variety of cancer cells. However data on ATX in myeloid leukemias and especially in AML are missing. To study more deeply the role of ATX in leukemogenesis, we screened a series of human leukemic model cell lines for ATX expression. Using retroviral transduction, two alternatively spliced transcripts of ATX were expressed in several human leukemic cell lines without detectable levels of endogenous ATX. To investigate the ATX function and expression in normal haematopoiesis we used CD34+ human progenitor cells. The expression of ATX transcripts was confirmed at both mRNA and protein levels by RT-PCR and Western blotting, respectively. Transwell migration assays in the presence of LPC or LPA were performed to study effects of ATX on cell motility. Proliferation and clonogenic potential were investigated using MTT and colony forming assays. Moreover, we examined the effect of the FLT3 inhibitor N-benzoylstaurosporine (PKC412) on ATX expression and ATX mediated migration in MV4-11 cells. High ATX expression was found primarily in malignant cells. Western blot analysis showed that detectable levels of ATX are secreted into medium within 2 hours. In normal cells, highest ATX mRNA expression was found in purified CD34 cells, but could also be found at lower levels in T-cells. Stable overexpression of FLT3-ITD in OCI-AML3 cells induced an increased ATX expression (up to 6 fold). Vice versa, inhibition of FLT3-ITD by sublethal doses of PKC412 in MV4-11 cells resulted in a significant reduction of ATX expression down to 10% of the initial expression level. Furthermore, PKC412 treatment resulted in a complete loss of LPC or LPA induced specific migratory capacity in MV4-11 cells. The transduction of ATX increased the colony-forming capacity by 75% and significantly increased the short term proliferation. LPA increased chemotaxis in human leukemic cell lines and human CD34+ progenitors in a dose dependent manner and induced significantly higher migratory rates by at least 50%. LPC induced chemotaxis by 80–200% only in cells with high expression of endogenous or exogenous ATX, demonstrating the autocrine activity of ATX. Ongoing studies on the mechanism of ATX expression showed that ionomycin, an activator of the Ca2+–calcineurin–NFAT signalling pathway, upregulated ATX mRNA in several leukemic cell lines as well as in human primary progenitors up to 5-fold, which could be completely blocked by cyclosporine A treatment, indicating an involvement of NFAT in the regulation of ATX. Our data suggest that the production of bioactive LPA through ATX is involved in controlling proliferation and migration of hematopoietic stem cells and its deregulation may contribute to the pathogenesis of AML, especially in patients with FLT3-ITD mutations.

Expression of Human Enhancer of Invasion 10 (HEI10) in Human Myeloid Leukemias and Downregulation during Differentiation of Hematopoietic Stem Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4290-4290
Author(s):  
Naohito Fujishima ◽  
Makoto Hirokawa ◽  
Masumi Fujishima ◽  
Yoshikazu Ichikawa ◽  
Takahiro Horiuchi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Chronic Phase ◽  
K562 Cells ◽  
Hematopoietic Stem ◽  
Expression Levels ◽  
Cd34 Cells

Abstract Background: We previously investigated the gene expression profile of drug-resistant human leukemia K562 cells by the serial analysis of gene expression (SAGE) (Ichikawa et al. Int J Hematol, 2004;79:276), and found that the HEI10 gene was overexpressed in K562 cells. With the same technology, we also observed that human CD34+ cells expressed high levels of HEI10 gene expression compared to erythroid progenitor cells (Fujishima et al. Int J Hematol, in press). HEI10 encodes a protein which belongs to a family of E3 ubiquitin ligase,and interacts with cyclin B1 leading to the regulation of cell cycle. In the present study, we examined the gene expression of HEI10 quantitatively in human leukemias in order to learn whether there would be any association between the expression levels and leukemia subtypes. We also investigated whether the expression levels of HEI10 would be related to differentiation of myeloid leukemia cell lines and normal hematopoietic stem cells. Methods: The quantitative real-time PCR method was employed to estimate the relative gene expression levels of HEI10. Total RNA was extracted from mononuclear cells of bone marrow that had been taken for diagnostic purposes. Patients include acute myeloid leukemia (AML) (n=21) and chronic myeloid leukemia (CML) (n=7; 2 in blastic crisis, 5 in chronic phase). Differentiation of human acute myeloid leukemia cell line HL60 cells was induced by PMA. Human normal CD34+ cells were purified from G-CSF mobilized blood stem cells and were induced to differentiate into erythroid, myeloid or dendritic cells by various cytokines. Results: Quantitative real-time PCR analysis revealed the high expression of HEI10 gene in patients with leukemia with undifferentiated phenotype (3 cases of AML M1 in FAB classification and 2 cases of CML in blast crisis) and low levels of expression in acute promyelocytic leukemia and CML in chronic phase. When HL60 cells were induced to differentiation with PMA, accumulation in the G0/G1 phase was observed and the expression of HEI10 was decreased. Differentiation of normal CD34+ cells also resulted in a decrease of HEI10 expression. Conclusions: The expression of HEI10 gene in hematopoietic cells appears to be upregulated when cells are immature. The role for HEI10 in hematopoietic stem cells remains to be elucidated. Biological effects of the HEI10 gene silencing in human hematopoietic cells are currently being investigated by RNAi technology. Figure Figure Figure Figure

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 Dissecting the Immune Cell Progeny of CAR-Expressing Hematopoietic Stem Cells in a Humanized Mouse Model

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4640-4640
Author(s):  
Heng-Yi Liu ◽  
Nezia Rahman ◽  
Tzu-Ting Chiou ◽  
Satiro N. De Oliveira
Keyword(s):  
Stem Cells ◽  
T Cells ◽  
T Cell ◽  
Hematopoietic Stem Cells ◽  
Cell Lines ◽  
Immune Cells ◽  
Research Funding ◽  
Humanized Mice ◽  
Tumor Challenge ◽  
Hematopoietic Stem

Background: Chemotherapy-refractory or recurrent B-lineage leukemias and lymphomas yield less than 50% of chance of cure. Therapy with autologous T-cells expressing chimeric antigen receptors (CAR) have led to complete remissions, but the effector cells may not persist, limiting clinical efficacy. Our hypothesis is the modification of hematopoietic stem cells (HSC) with anti-CD19 CAR will lead to persistent generation of multilineage target-specific immune cells, enhancing graft-versus-cancer activity and leading to development of immunological memory. Design/Methods: We generated second-generation CD28- and 4-1BB-costimulated CD19-specific CAR constructs using third-generation lentiviral vectors for modification of human HSC for assessment in vivo in NSG mice engrafted neonatally with human CD34-positive cells. Cells were harvested from bone marrows, spleens, thymus and peripheral blood at different time points for evaluation by flow cytometry and ddPCR for vector copy numbers. Cohorts of mice received tumor challenge with subcutaneous injection of lymphoma cell lines. Results: Gene modification of HSC with CD19-specific CAR did not impair differentiation or proliferation in humanized mice, leading to CAR-expressing cell progeny in myeloid, NK and T-cells. Humanized NSG engrafted with CAR-modified HSC presented similar humanization rates to non-modified HSC, with multilineage CAR-expressing cells present in all tissues with stable levels up to 44 weeks post-transplant. No animals engrafted with CAR-modified HSC presented autoimmunity or inflammation. T-cell populations were identified at higher rates in humanized mice with CAR-modified HSC in comparison to mice engrafted with non-modified HSC. CAR-modified HSC led to development of T-cell effector memory and T-cell central memory phenotypes, confirming the development of long-lasting phenotypes due to directed antigen specificity. Mice engrafted with CAR-modified HSC successfully presented tumor growth inhibition and survival advantage at tumor challenge with lymphoma cell lines, with no difference between both constructs (62.5% survival for CD28-costimulated CAR and 66.6% for 41BB-costimulated CAR). In mice sacrificed due to tumor development, survival post-tumor injection was directly correlated with tumor infiltration by CAR T-cells. Conclusions: CAR modification of human HSC for cancer immunotherapy is feasible and continuously generates CAR-bearing cells in multiple lineages of immune cells. Targeting of different malignancies can be achieved by adjusting target specificity, and this approach can augment the anti-lymphoma activity in autologous HSC recipients. It bears decreased morbidity and mortality and offers alternative therapeutic approach for patients with no available sources for allogeneic transplantation, benefiting ethnic minorities. Disclosures De Oliveira: National Institute for Health Research Biomedical Research Centre at Great Ormond Street Hospital for Children NHS Foundation Trust and University College London: Research Funding; NIAID, NHI: Research Funding; Medical Research Council: Research Funding; CIRM: Research Funding; National Gene Vector Repository: Research Funding.

scholarly journals Deletion of PI3-Kinase Promotes Myelodysplasia Through Dysregulation of Autophagy in Hematopoietic Stem Cells

2020 ◽  
Author(s):  
Kristina Ames ◽  
Imit Kaur ◽  
Yang Shi ◽  
Meng Tong ◽  
Taneisha Sinclair ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Chromosomal Abnormalities ◽  
Akt Pathway ◽  
Hematopoietic Growth Factors ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Hematopoietic System ◽  
Phosphoinositide 3 Kinase

AbstractHematopoietic stem cells (HSCs) maintain the blood system through a delicate equilibrium between self-renewal and differentiation. Most hematopoietic growth factors and cytokines signal through phosphoinositide 3-kinase (PI3K) via three Class IA catalytic PI3K isoforms (P110α, β, and δ), encoded by Pik3ca, Pik3cb, and Pik3cd, respectively. The PI3K/AKT pathway is commonly activated in acute myeloid leukemia (AML), and PI3K is a common therapeutic target in cancer. However, it is not known whether PI3K is required for HSC differentiation or self-renewal. We previously demonstrated that individual PI3K isoforms are dispensable in HSCs1,2. To determine the redundant roles of PI3K isoforms in HSCs, we generated a triple knockout (TKO) mouse model with deletion of all three Class IA PI3K isoforms in the hematopoietic system. Surprisingly, we observed significant expansion of TKO HSCs after transplantation, with decreased differentiation capacity and impaired multilineage repopulation. Additionally, the bone marrow of TKO mice exhibited myelodysplastic features with chromosomal abnormalities. Interestingly, we found that macroautophagy (thereafter autophagy) is impaired in TKO HSCs, and that pharmacologic induction of autophagy improves their differentiation. Therefore, we have uncovered important roles for PI3K in autophagy regulation in HSCs to maintain the balance between self-renewal and differentiation.

Arsenic Trioxide and Melarsoprol Induce Programmed Cell Death in Myeloid Leukemia Cell Lines and Function in a PML and PML-RAR Independent Manner

Blood ◽  
1998 ◽  
Vol 92 (5) ◽  
pp. 1497-1504 ◽  
Author(s):  
Zhu-Gang Wang ◽  
Roberta Rivi ◽  
Laurent Delva ◽  
Andrea König ◽  
David A. Scheinberg ◽  
...  
Keyword(s):  
Cell Line ◽  
Arsenic Trioxide ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Nuclear Bodies ◽  
Independent Manner ◽  
Leukemia Cell Lines ◽  
Induced Apoptosis ◽  
Myeloid Leukemia Cell

Abstract Inorganic arsenic trioxide (As2O3) and the organic arsenical, melarsoprol, were recently shown to inhibit growth and induce apoptosis in NB4 acute promyelocytic leukemia (APL) and chronic B-cell leukemia cell lines, respectively. As2O3 has been proposed to principally target PML and PML-RAR proteins in APL cells. We investigated the activity of As2O3 and melarsoprol in a broader context encompassing various myeloid leukemia cell lines, including the APL cell line NB4-306 (a retinoic acid–resistant cell line derived from NB4 that no longer expresses the intact PML-RAR fusion protein), HL60, KG-1, and the myelomonocytic cell line U937. To examine the role of PML in mediating arsenical activity, we also tested these agents using murine embryonic fibroblasts (MEFs) and bone marrow (BM) progenitors in which the PML gene had been inactivated by homologous recombination. Unexpectedly, we found that both compounds inhibited cell growth, induced apoptosis, and downregulated bcl-2 protein in all cell lines tested. Melarsoprol was more potent than As2O3 at equimolar concentrations ranging from 10−7 to 10−5 mol/L. As2O3 relocalized PML and PML-RAR onto nuclear bodies, which was followed by PML degradation in NB4 as well as in HL60 and U937 cell lines. Although melarsoprol was more potent in inhibiting growth and inducing apoptosis, it did not affect PML and/or PML-RAR nuclear localization. Moreover, both As2O3 and melarsoprol comparably inhibited growth and induced apoptosis of PML+/+ and PML−/− MEFs, and inhibited colony-forming unit erythroid (CFU-E) and CFU granulocyte-monocyte formation in BM cultures of PML+/+ and PML−/− progenitors. Together, these results show that As2O3 and melarsoprol inhibit growth and induce apoptosis independent of both PML and PML-RAR expression in a variety of myeloid leukemia cell lines, and suggest that these agents may be more broadly used for treatment of leukemias other than APL. © 1998 by The American Society of Hematology.

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