101
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Abstract
Fetal liver and adult bone marrow hematopoietic stem cells (HSCs) renew or differentiate into committed progenitors to generate all blood cells. PRDM16 is involved in human leukemic translocations and is expressed highly in some karyotypically normal acute myeloblastic leukemias. As many genes involved in leukemogenic fusions play a role in normal hematopoiesis, we analyzed the role of Prdm16 in the biology of HSCs using Prdm16-deficient mice. We show here that, within the hematopoietic system, Prdm16 is expressed very selectively in the earliest stem and progenitor compartments, and, consistent with this expression pattern, is critical for the establishment and maintenance of the HSC pool during development and after transplantation. Prdm16 deletion enhances apoptosis and cycling of HSCs. Expression analysis revealed that Prdm16 regulates a remarkable number of genes that, based on knockout models, both enhance and suppress HSC function, and affect quiescence, cell cycling, renewal, differentiation, and apoptosis to various extents. These data suggest that Prdm16 may be a critical node in a network that contains negative and positive feedback loops and integrates HSC renewal, quiescence, apoptosis, and differentiation.
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102
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Negrotto S, Hu Z, Alcazar O, Ng KP, Triozzi P, Lindner D, Rini B, Saunthararajah Y. Noncytotoxic differentiation treatment of renal cell cancer. Cancer Res 2011; 71:1431-41. [PMID: 21303982 DOI: 10.1158/0008-5472.can-10-2422] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Current drug therapy for metastatic renal cell cancer (RCC) results in temporary disease control but not cure, necessitating continued investigation into alternative mechanistic approaches. Drugs that inhibit chromatin-modifying enzymes involved in transcription repression (chromatin-relaxing drugs) could have a role, by inducing apoptosis and/or through differentiation pathways. At low doses, the cytosine analogue decitabine (DAC) can be used to deplete DNA methyl-transferase 1 (DNMT1), modify chromatin, and alter differentiation without causing apoptosis (cytotoxicity). Noncytotoxic regimens of DAC were evaluated for in vitro and in vivo efficacy against RCC cell lines, including a p53-mutated RCC cell line developed from a patient with treatment-refractory metastatic RCC. The cell division-permissive mechanism of action-absence of early apoptosis or DNA damage, increase in expression of HNF4α (hepatocyte nuclear factor 4α), a key driver associated with the mesenchymal to epithelial transition, decrease in mesenchymal marker expression, increase in epithelial marker expression, and late increase in cyclin-dependent kinase inhibitor CDKN1B (p27) protein-was consistent with differentiation-mediated cell-cycle exit. In vivo blood counts and animal weights were consistent with minimal toxicity of therapy. The distinctive mechanism of action of a dose and schedule of DAC designed for noncytotoxic depletion of DNMT1 suggests a potential role in treating RCC.
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Affiliation(s)
- Soledad Negrotto
- Department of Translational Hematology and Oncology Research, Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio, USA
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103
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Montanaro L. Dyskerin and cancer: more than telomerase. The defect in mRNA translation helps in explaining how a proliferative defect leads to cancer. J Pathol 2010; 222:345-9. [PMID: 20925138 DOI: 10.1002/path.2777] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 09/02/2010] [Indexed: 01/18/2023]
Abstract
Point mutations in the DKC1 gene that encodes dyskerin cause the rare inherited syndrome called X-linked dyskeratosis congenita, characterized by a failure of proliferating tissues and increased susceptibility to cancer. Dyskerin is a nucleolar protein with different functions, all fundamental to basic cellular events such as protein expression, growth, and proliferation. The two best-characterized dyskerin activities are the stabilization of the telomerase RNA component, allowing the proper function telomerase enzymatic complex, and the modification of specific uridine residues of ribosomal RNA by converting them to pseudouridine, thus allowing proper ribosome processing and function. In light of the recent findings, this review focuses on the molecular pathogenesis of dyskeratosis congenita, discussing how a defect in ribosomal function might impact on the translation of a subset of mRNAs encoding for tumour suppressors, thus providing an explanation for the apparent paradox of dyskeratosis congenita in which reduced cell proliferation is associated with cancer susceptibility. In addition, the current evidence pointing to a role played by dyskerin in tumours in the general population is also discussed.
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Affiliation(s)
- Lorenzo Montanaro
- Department of Experimental Pathology, Alma Mater Studiorum--Università di Bologna, Bologna, Italy.
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104
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Trikha P, Sharma N, Opavsky R, Reyes A, Pena C, Ostrowski MC, Roussel MF, Leone G. E2f1-3 are critical for myeloid development. J Biol Chem 2010; 286:4783-95. [PMID: 21115501 DOI: 10.1074/jbc.m110.182733] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Hematopoietic development involves the coordinated activity of differentiation and cell cycle regulators. In current models of mammalian cell cycle control, E2f activators (E2f1, E2f2, and E2f3) are portrayed as the ultimate transcriptional effectors that commit cells to enter and progress through S phase. Using conditional gene knock-out strategies, we show that E2f1-3 are not required for the proliferation of early myeloid progenitors. Rather, these E2fs are critical for cell survival and proliferation at two distinct steps of myeloid development. First, E2f1-3 are required as transcriptional repressors for the survival of CD11b(+) myeloid progenitors, and then they are required as activators for the proliferation of CD11b(+) macrophages. In bone marrow macrophages, we show that E2f1-3 respond to CSF1-Myc mitogenic signals and serve to activate E2f target genes and promote their proliferation. Together, these findings expose dual functions for E2f1-3 at distinct stages of myeloid development in vivo, first as repressors in cell survival and then as activators in cell proliferation. In summary, this work places E2f1-3 in a specific signaling cascade that is critical for myeloid development in vivo.
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Affiliation(s)
- Prashant Trikha
- College of Medicine and Public Health, Ohio State University, Columbus, Ohio 43210, USA
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105
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Sirin O, Lukov GL, Mao R, Conneely OM, Goodell MA. The orphan nuclear receptor Nurr1 restricts the proliferation of haematopoietic stem cells. Nat Cell Biol 2010; 12:1213-9. [PMID: 21076412 PMCID: PMC3059561 DOI: 10.1038/ncb2125] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 10/18/2010] [Indexed: 12/15/2022]
Abstract
Successful haematopoiesis requires long-term retention of haematopoietic stem cells (HSCs) in a quiescent state. The transcriptional regulation of stem cell quiescence, especially by factors with specific functions in HSCs, is only beginning to be understood. Here, we demonstrate that Nurr1, a nuclear receptor transcription factor, has such a regulatory role. Overexpression of Nurr1 drives early haematopoietic progenitors into quiescence. When stem cells overexpressing Nurr1 are transplanted into lethally irradiated mice, they localize to the bone marrow, but do not contribute to regeneration of the blood system. Furthermore, the loss of only one allele of Nurr1 is sufficient to induce HSCs to enter the cell cycle and proliferate. Molecular analysis revealed an association between Nurr1 overexpression and upregulation of the cell-cycle inhibitor p18 (also known as INK4C), suggesting a mechanism by which Nurr1 could regulate HSC quiescence. Our findings provide critical insight into the transcriptional control mechanisms that determine whether HSCs remain dormant or enter the cell cycle and begin to proliferate.
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Affiliation(s)
- Olga Sirin
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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106
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Verrucci M, Pancrazzi A, Aracil M, Martelli F, Guglielmelli P, Zingariello M, Ghinassi B, D'Amore E, Jimeno J, Vannucchi AM, Migliaccio AR. CXCR4-independent rescue of the myeloproliferative defect of the Gata1low myelofibrosis mouse model by Aplidin. J Cell Physiol 2010; 225:490-9. [PMID: 20458749 DOI: 10.1002/jcp.22228] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The discovery of JAK2 mutations in Philadelphia-negative myeloproliferative neoplasms has prompted investigators to evaluate mutation-targeted treatments to restore hematopoietic cell functions in these diseases. However, the results of the first clinical trials with JAK2 inhibitors are not as promising as expected, prompting a search for additional drugable targets to treat these disorders. In this paper, we used the hypomorphic Gata1(low) mouse model of primary myelofibrosis (PMF), the most severe of these neoplasms, to test the hypothesis that defective marrow hemopoiesis and development of extramedullary hematopoiesis in myelofibrosis is due to insufficient p27(Kip1) activity and is treatable by Aplidin, a cyclic depsipeptide that activates p27(Kip1) in several cancer cells. Aplidin restored expression of Gata1 and p27(Kip1) in Gata1(low) hematopoietic cells, proliferation of marrow progenitor cells in vitro and maturation of megakaryocytes in vivo (reducing TGF-beta/VEGF levels released in the microenvironment by immature Gata1(low) megakaryocytes). Microvessel density, fibrosis, bone growth, and marrow cellularity were normal in Aplidin-treated mice and extramedullary hematopoiesis did not develop in liver although CXCR4 expression in Gata1(low) progenitor cells remained low. These results indicate that Aplidin effectively alters the natural history of myelofibrosis in Gata1(low) mice and suggest this drug as candidate for clinical evaluation in PMF.
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Affiliation(s)
- Maria Verrucci
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
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107
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Cohn E, Ossowski L, Bertran S, Marzan C, Farias EF. RARα1 control of mammary gland ductal morphogenesis and wnt1-tumorigenesis. Breast Cancer Res 2010; 12:R79. [PMID: 20923554 PMCID: PMC3096972 DOI: 10.1186/bcr2724] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 10/05/2010] [Indexed: 01/16/2023] Open
Abstract
INTRODUCTION Retinoic acid signaling pathways are disabled in human breast cancer suggesting a controlling role in normal mammary growth that might be lost in tumorigenesis. We tested a single receptor isotype, RARα1, for its role in mouse mammary gland morphogenesis and MMTV-wnt1-induced oncogenesis. METHODS The role of RARα1 in mammary morphogenesis was tested in RARα1-knockout (KO) mice and in mammary tumorigenesis in bi-genic (RARα1/KO crossed with MMTV-wnt1) mice. We used whole mounts analysis, stem cells/progenitor quantification, mammary gland repopulation, Q-PCR, test of tumor-free survival, tumor fragments and cell transplantation. RESULTS In 2 genetic backgrounds (129/Bl-6 and FVB) the neo-natal RARα1/KO-mammary epithelial tree was 2-fold larger and the pubertal tree had 2-fold more branch points and 5-fold more mature end buds, a phenotype that was predominantly epithelial cell autonomous. The stem/progenitor compartment of the RARα1/KO mammary, defined as CD24(low)/ALDH(high activity) was increased by a median 1.7 fold, but the mammary stem cell (MaSC)-containing compartment, (CD24(low)/CD29(high)), was larger (~1.5 fold) in the wt-glands, and the mammary repopulating ability of the wt-gland epithelium was ~2-fold greater. In MMTV-wnt1 transgenic glands the progenitor (CD24(low)/ALDH(high activity)) content was 2.6-fold greater than in the wt and was further increased in the RARα1/KO-wnt1 glands. The tumor-free survival of RARα1/KO-wnt1 mice was significantly (p=0.0002, Kaplan Meier) longer, the in vivo growth of RARα1/KO-wnt1 transplanted tumor fragments was significantly (p=0.01) slower and RARα1/KO-wnt1 tumors cell suspension produced tumors after much longer latency. CONCLUSIONS In vitamin A-replete mice, RARα1 is required to maintain normal mammary morphogenesis, but paradoxically, also efficient tumorigenesis. While its loss increases the density of the mammary epithelial tree and the content of luminal mammary progenitors, it appears to reduce the size of the MaSC-containing compartment, the mammary repopulating activity, and to delay significantly the MMTV-wnt1-mammary tumorigenesis. Whether the delay in tumorigenesis is solely due to a reduction in wnt1 target cells or due to additional mechanisms remains to be determined. These results reveal the intricate nature of the retinoid signaling pathways in mammary development and carcinogenesis and suggest that a better understanding will be needed before retinoids can join the armament of effective anti- breast cancer therapies.
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Affiliation(s)
- Ellen Cohn
- Division of Hematology/Oncology, Tisch Cancer Institute, Mount Sinai School of Medicine, New York, NY 10029, USA
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108
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Abstract
Steady-state hematopoiesis is sustained through differentiation balanced with proliferation and self-renewal of hematopoietic stem cells (HSCs). Disruption of this balance can lead to hematopoietic failure, as hematopoietic differentiation without self-renewal leads to loss of the HSC pool. We find that conditional knockout mice that delete the transcriptional repressor NKAP in HSCs and all hematopoietic lineages during embryonic development exhibit perinatal lethality and abrogation of hematopoiesis as demonstrated by multilineage defects in lymphocyte, granulocyte, erythrocyte and megakaryocyte development. Inducible deletion of NKAP in adult mice leads to lethality within 2 weeks, at which point hematopoiesis in the bone marrow has halted and HSCs have disappeared. This hematopoietic failure and lethality is cell intrinsic, as radiation chimeras reconstituted with inducible Mx1-cre NKAP conditional knockout bone marrow also succumb with a similar time course. Even in the context of a completely normal bone marrow environment using mixed radiation chimeras, NKAP deletion results in HSC failure. NKAP deletion leads to decreased proliferation and increased apoptosis of HSCs, which is likely due to increased expression of the cyclin-dependent kinase inhibitors p21Cip1/Waf1 and p19Ink4d. These data establish NKAP as one of a very small number of transcriptional regulators that is absolutely required for adult HSC maintenance and survival.
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109
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Miyata Y, Liu Y, Jankovic V, Sashida G, Lee JM, Shieh JH, Naoe T, Moore M, Nimer SD. Cyclin C regulates human hematopoietic stem/progenitor cell quiescence. Stem Cells 2010; 28:308-17. [PMID: 19967789 DOI: 10.1002/stem.270] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hematopoietic stem cells (HSCs) can remain quiescent or they can enter the cell cycle, and either self-renew or differentiate. Although cyclin C and cyclin dependent kinase (cdk3) are essential for the transition from the G(0) to the G(1) phase of the cell cycle in human fibroblasts, the role of cyclin C in hematopoietic stem/progenitor cells (HSPCs) is not clear. We have identified an important role of cyclin C (CCNC) in regulating human HSPC quiescence, as knocking down CCNC expression in human cord blood CD34(+) cells resulted in a significant increase in quiescent cells that maintain CD34 expression. CCNC knockdown also promotes in vitro HSPC expansion and enhances their engraftment potential in sublethally irradiated immunodeficient mice. Our studies establish cyclin C as a critical regulator of the G(0)/G(1) transition of human HSPCs and suggest that modulating cyclin C levels may be useful for HSC expansion and more efficient engraftment.
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Affiliation(s)
- Yasuhiko Miyata
- Molecular Pharmacology and Chemistry Program and Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA
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110
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Hypoxia mediates low cell-cycle activity and increases the proportion of long-term–reconstituting hematopoietic stem cells during in vitro culture. Exp Hematol 2010; 38:301-310.e2. [DOI: 10.1016/j.exphem.2010.01.005] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 01/12/2010] [Accepted: 01/22/2010] [Indexed: 02/07/2023]
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111
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Paik JH, Ding Z, Narurkar R, Ramkissoon S, Muller F, Kamoun WS, Chae SS, Zheng H, Ying H, Mahoney J, Hiller D, Jiang S, Protopopov A, Wong WH, Chin L, Ligon KL, DePinho RA. FoxOs cooperatively regulate diverse pathways governing neural stem cell homeostasis. Cell Stem Cell 2010; 5:540-53. [PMID: 19896444 DOI: 10.1016/j.stem.2009.09.013] [Citation(s) in RCA: 352] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 07/01/2009] [Accepted: 09/28/2009] [Indexed: 10/20/2022]
Abstract
The PI3K-AKT-FoxO pathway is integral to lifespan regulation in lower organisms and essential for the stability of long-lived cells in mammals. Here, we report the impact of combined FoxO1, 3, and 4 deficiencies on mammalian brain physiology with a particular emphasis on the study of the neural stem/progenitor cell (NSC) pool. We show that the FoxO family plays a prominent role in NSC proliferation and renewal. FoxO-deficient mice show initial increased brain size and proliferation of neural progenitor cells during early postnatal life, followed by precocious significant decline in the NSC pool and accompanying neurogenesis in adult brains. Mechanistically, integrated transcriptomic, promoter, and functional analyses of FoxO-deficient NSC cultures identified direct gene targets with known links to the regulation of human brain size and the control of cellular proliferation, differentiation, and oxidative defense. Thus, the FoxO family coordinately regulates diverse genes and pathways to govern key aspects of NSC homeostasis in the mammalian brain.
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Affiliation(s)
- Ji-hye Paik
- Department of Medical Oncology, Belfer Institute for Applied Cancer Science, Harvard Medical School, Boston, MA 02115, USA
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112
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Role of BCR-ABL-Y177-mediated p27kip1 phosphorylation and cytoplasmic localization in enhanced proliferation of chronic myeloid leukemia progenitors. Leukemia 2010; 24:779-87. [PMID: 20200561 PMCID: PMC2854856 DOI: 10.1038/leu.2010.24] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In chronic myelogenous leukemia (CML) hematopoietic stem cell transformation leads to increased proliferation of malignant myeloid progenitors. The cyclin-dependent kinase inhibitor p27kip1 (p27) is a critical negative regulator of hematopoietic progenitor proliferation and pool size that is deregulated in BCR-ABL expressing cell lines. However, cell-context specific regulation of p27 in primary human CML progenitors and its contribution to CML progenitor expansion remain unclear. Here we investigated p27 regulation and function in (1) CD34+ cells from CML patients and (2) human CD34+ cells ectopically expressing the BCR-ABL gene following retrovirus transduction. We found that p27 levels are increased in CML CD34+ cells related to a BCR-ABL dependent increase in p27 protein translation. However p27 was relocated to the cytoplasm in CML progenitors and nuclear p27 levels were reduced, allowing increased cell cycling and expansion in culture. Cytoplasmic relocation of p27 in CML progenitors was related to signaling through BCR-ABL Y177, activation of the AKT kinase and phosphorylation of p27 on Thr-157 (T157). Expression of a mutant p27 that cannot be phosphorylated on T157 significant inhibited CML progenitor proliferation. These studies demonstrate the importance of BCR-ABL-Y177-AKT mediated p27 phosphorylation in altered p27 localization and enhanced proliferation and expansion of primary CML progenitors.
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113
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Abstract
CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) possess the capacity to modulate both adaptive and innate immune responses. We hypothesized that Tregs could regulate hematopoiesis based on cytokine effector molecules they can produce. The studies here demonstrate that Tregs can affect the differentiation of myeloid progenitor cells. In vitro findings demonstrated the ability of Tregs to inhibit the differentiation of interleukin-3 (IL-3)/stem cell factor (colony-forming unit [CFU]-IL3)-driven progenitor cells. Inhibitory effects were mediated by a pathway requiring cell-cell contact, major histocompatibility complex class II expression on marrow cells, and transforming growth factor-beta. Importantly, depletion of Tregs in situ resulted in enhanced CFU-IL3 levels after bone marrow transplantation. Cotransplantation of CD4(+)FoxP3(+)(gfp) Tregs together with bone marrow was found to diminish CFU-IL3 responses after transplantation. To address the consequence of transplanted Tregs on differentiated progeny from these CFU 2 weeks after hematopoietic stem cell transplantation, peripheral blood complete blood counts were performed and examined for polymorphonuclear leukocyte content. Recipients of cotransplanted Tregs exhibited diminished neutrophil counts. Together, these findings illustrate that both recipient and donor Tregs can influence hematopoietic progenitor cell activity after transplantation and that these cells can alter responses outside the adaptive and innate immune systems.
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114
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Banerjee P, Crawford L, Samuelson E, Feuer G. Hematopoietic stem cells and retroviral infection. Retrovirology 2010; 7:8. [PMID: 20132553 PMCID: PMC2826343 DOI: 10.1186/1742-4690-7-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Accepted: 02/04/2010] [Indexed: 11/10/2022] Open
Abstract
Retroviral induced malignancies serve as ideal models to help us better understand the molecular mechanisms associated with the initiation and progression of leukemogenesis. Numerous retroviruses including AEV, FLV, M-MuLV and HTLV-1 have the ability to infect hematopoietic stem and progenitor cells, resulting in the deregulation of normal hematopoiesis and the development of leukemia/lymphoma. Research over the last few decades has elucidated similarities between retroviral-induced leukemogenesis, initiated by deregulation of innate hematopoietic stem cell traits, and the cancer stem cell hypothesis. Ongoing research in some of these models may provide a better understanding of the processes of normal hematopoiesis and cancer stem cells. Research on retroviral induced leukemias and lymphomas may identify the molecular events which trigger the initial cellular transformation and subsequent maintenance of hematologic malignancies, including the generation of cancer stem cells. This review focuses on the role of retroviral infection in hematopoietic stem cells and the initiation, maintenance and progression of hematological malignancies.
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Affiliation(s)
- Prabal Banerjee
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Center for Humanized SCID Mice and Stem Cell Processing Laboratory, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Lindsey Crawford
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Elizabeth Samuelson
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Gerold Feuer
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Center for Humanized SCID Mice and Stem Cell Processing Laboratory, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
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115
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Abstract
Self-renewal is the process by which stem cells divide to make more stem cells, perpetuating the stem cell pool throughout life. Self-renewal is division with maintenance of the undifferentiated state. This requires cell cycle control and often maintenance of multipotency or pluripotency, depending on the stem cell. Self-renewal programs involve networks that balance proto-oncogenes (promoting self-renewal), gate-keeping tumor suppressors (limiting self-renewal), and care-taking tumor suppressors (maintaining genomic integrity). These cell-intrinsic mechanisms are regulated by cell-extrinsic signals from the niche, the microenvironment that maintains stem cells and regulates their function in tissues. In response to changing tissue demands, stem cells undergo changes in cell cycle status and developmental potential over time, requiring different self-renewal programs at different stages of life. Reduced stem cell function and tissue regenerative capacity during aging are caused by changes in self-renewal programs that augment tumor suppression. Cancer arises from mutations that inappropriately activate self-renewal programs.
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Affiliation(s)
- Shenghui He
- Howard Hughes Medical Institute, Life Sciences Institute, Department of Internal Medicine, Center for Stem Cell Biology, University of Michigan, Ann Arbor, Michigan 48109-2216, USA
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116
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Defects in osteoblast function but no changes in long-term repopulating potential of hematopoietic stem cells in a mouse chronic inflammatory arthritis model. Blood 2009; 114:4402-10. [PMID: 19759358 DOI: 10.1182/blood-2008-12-196311] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Recent studies support the notion that there is an intricate relationship between hematopoiesis and bone homeostasis in normal steady states. Using mice undergoing chronic inflammatory arthritis, we investigated the relationship between hematopoiesis and bone homeostasis in pathologic conditions. We demonstrate that mice undergoing chronic inflammatory arthritis displayed osteoporosis resulting from a severe defect in osteoblast function. Despite the defective osteoblast function, however, the hematopoietic stem cells from these mice exhibited normal properties in either long-term repopulation or cell cycling. Therefore, the bone-forming capacity of osteoblasts is distinct from their ability to maintain hematopoietic stem cells in chronic inflammatory conditions.
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117
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Loss of the Rho GTPase activating protein p190-B enhances hematopoietic stem cell engraftment potential. Blood 2009; 114:3557-66. [PMID: 19713466 DOI: 10.1182/blood-2009-02-205815] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Hematopoietic stem cell (HSC) engraftment is a multistep process involving HSC homing to bone marrow, self-renewal, proliferation, and differentiation to mature blood cells. Here, we show that loss of p190-B RhoGTPase activating protein, a negative regulator of Rho GTPases, results in enhanced long-term engraftment during serial transplantation. This effect is associated with maintenance of functional HSC-enriched cells. Furthermore, loss of p190-B led to marked improvement of HSC in vivo repopulation capacity during ex vivo culture without altering proliferation and multilineage differentiation of HSC and progeny. Transcriptional analysis revealed that p190-B deficiency represses the up-regulation of p16(Ink4a) in HSCs in primary and secondary transplantation recipients, providing a possible mechanism of p190-B-mediated HSC functions. Our study defines p190-B as a critical transducer element of HSC self-renewal activity and long-term engraftment, thus suggesting that p190-B is a target for HSC-based therapies requiring maintenance of engraftment phenotype.
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118
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Petit-Bertron AF, Machavoine F, Defresne MP, Gillard M, Chatelain P, Mistry P, Schneider E, Dy M. H4 histamine receptors mediate cell cycle arrest in growth factor-induced murine and human hematopoietic progenitor cells. PLoS One 2009; 4:e6504. [PMID: 19662098 PMCID: PMC2720606 DOI: 10.1371/journal.pone.0006504] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 07/01/2009] [Indexed: 01/15/2023] Open
Abstract
The most recently characterized H4 histamine receptor (H4R) is expressed preferentially in the bone marrow, raising the question of its role during hematopoiesis. Here we show that both murine and human progenitor cell populations express this receptor subtype on transcriptional and protein levels and respond to its agonists by reduced growth factor-induced cell cycle progression that leads to decreased myeloid, erythroid and lymphoid colony formation. H4R activation prevents the induction of cell cycle genes through a cAMP/PKA-dependent pathway that is not associated with apoptosis. It is mediated specifically through H4R signaling since gene silencing or treatment with selective antagonists restores normal cell cycle progression. The arrest of growth factor-induced G1/S transition protects murine and human progenitor cells from the toxicity of the cell cycle-dependent anticancer drug Ara-C in vitro and reduces aplasia in a murine model of chemotherapy. This first evidence for functional H4R expression in hematopoietic progenitors opens new therapeutic perspectives for alleviating hematotoxic side effects of antineoplastic drugs.
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Affiliation(s)
| | - François Machavoine
- Université Paris Descartes, Faculté de Médecine, CNRS UMR8147, Hôpital Necker, Paris, France
| | | | - Michel Gillard
- UCB S.A. Pharma, Chemin du Friest, Braine-l’Alleud, Belgium
| | | | | | - Elke Schneider
- Université Paris Descartes, Faculté de Médecine, CNRS UMR8147, Hôpital Necker, Paris, France
- * E-mail:
| | - Michel Dy
- Université Paris Descartes, Faculté de Médecine, CNRS UMR8147, Hôpital Necker, Paris, France
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119
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Kinetics of normal hematopoietic stem and progenitor cells in a Notch1-induced leukemia model. Blood 2009; 114:3783-92. [PMID: 19652197 DOI: 10.1182/blood-2009-06-227843] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The predominant outgrowth of malignant cells over their normal counterparts in a given tissue is a shared feature for all types of cancer. However, the impact of a cancer environment on normal tissue stem and progenitor cells has not been thoroughly investigated. We began to address this important issue by studying the kinetics and functions of hematopoietic stem and progenitor cells in mice with Notch1-induced leukemia. Although hematopoiesis was progressively suppressed during leukemia development, the leukemic environment imposed distinct effects on hematopoietic stem and progenitor cells, thereby resulting in different outcomes. The normal hematopoietic stem cells in leukemic mice were kept in a more quiescent state but remained highly functional on transplantation to nonleukemic recipients. In contrast, the normal hematopoietic progenitor cells in leukemic mice demonstrated accelerated proliferation and exhaustion. Subsequent analyses on multiple cell-cycle parameters and known regulators (such as p21, p27, and p18) further support this paradigm. Therefore, our current study provides definitive evidence and plausible underlying mechanisms for hematopoietic disruption but reversible inhibition of normal hematopoietic stem cells in a leukemic environment. It may also have important implications for cancer prevention and treatment in general.
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120
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Qiu J, Takagi Y, Harada J, Topalkara K, Wang Y, Sims JR, Zheng G, Huang P, Ling Y, Scadden DT, Moskowitz MA, Cheng T. p27Kip1 constrains proliferation of neural progenitor cells in adult brain under homeostatic and ischemic conditions. Stem Cells 2009; 27:920-7. [PMID: 19353520 DOI: 10.1002/stem.1] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cell cycle inhibition of neural stem and progenitor cells is critical for maintaining the stability of central nervous system in adults, but it may represent a significant hurdle for neural regeneration after injury. We have previously demonstrated that the cyclin-dependent kinase inhibitor (CKI) p21(cip1/waf1) (p21) maintains the quiescence of neural stem-like cells under cerebral ischemia, as similarly shown for the hematopoietic stem cells. Here, we report the distinct role of another CKI member, p27(kip1) (p27) in neural progenitor cells (NPCs) from adult brain (subventricular zone and hippocampal subgranular zone) under both homeostatic and ischemic conditions. The basal level of NPC proliferation in the p27-/- mice was higher than that in p27+/+ mice. Upon ischemia, the overall proliferation of NPCs continued to be higher in p27-/- mice than that in p27+/+ mice. Moreover, the increase of NPC proliferation in p27-/- mice remained until 2 weeks after ischemia, whereas it resumed back to the basal level in p27+/+ mice. As a result, newly generated neuronal cells in the granular layer of p27-/- brain were more abundant compared with p27+/+ controls. These new data demonstrate that p27 functions as a distinct inhibitor for NPC proliferation under homeostatic as well as ischemic conditions.
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Affiliation(s)
- Jianhua Qiu
- Department of Radiology and Neurology, Stroke and Neurovascular Regulation Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02129, USA.
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121
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Prospective isolation and molecular characterization of hematopoietic stem cells with durable self-renewal potential. Blood 2009; 113:6342-50. [PMID: 19377048 DOI: 10.1182/blood-2008-12-192054] [Citation(s) in RCA: 240] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Hematopoietic stem cells (HSCs) are generally defined by their dual properties of pluripotency and extensive self-renewal capacity. However, a lack of experimental clarity as to what constitutes extensive self-renewal capacity coupled with an absence of methods to prospectively isolate long-term repopulating cells with defined self-renewal activities has made it difficult to identify the essential components of the self-renewal machinery and investigate their regulation. We now show that cells capable of repopulating irradiated congenic hosts for 4 months and producing clones of cells that can be serially transplanted are selectively and highly enriched in the CD150(+) subset of the EPCR(+)CD48(-)CD45(+) fraction of mouse fetal liver and adult bone marrow cells. In contrast, cells that repopulate primary hosts for the same period but show more limited self-renewal activity are enriched in the CD150(-) subset. Comparative transcriptome analyses of these 2 subsets with each other and with HSCs whose self-renewal activity has been rapidly extinguished in vitro revealed 3 new genes (VWF, Rhob, Pld3) whose elevated expression is a consistent and selective feature of the long-term repopulating cells with durable self-renewal capacity. These findings establish the identity of a phenotypically and molecularly distinct class of pluripotent hematopoietic cells with lifelong self-renewal capacity.
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122
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Reduced c-Myb activity compromises HSCs and leads to a myeloproliferation with a novel stem cell basis. EMBO J 2009; 28:1492-504. [PMID: 19360001 DOI: 10.1038/emboj.2009.97] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 03/20/2009] [Indexed: 01/08/2023] Open
Abstract
Murine haematopoietic stem cells (HSCs) are contained in the Kit+Sca1+Lin(-) (KSL) population of bone marrow and are able to repopulate lethally irradiated mice. Myeloproliferative disorders (MPDs) are thought to be clonogenic diseases arising at the level of the HSC. Here, we show that mice expressing low levels of the transcription factor c-Myb, as the result of genetic knockdown, develop a transplantable myeloproliferative phenotype that closely resembles the human disease essential thrombocythaemia (ET). Unlike wild-type cells, the KSL population in c-myb knockdown bone marrow cannot repopulate irradiated mice and does not transfer the disease. Instead, cells positive for Kit and expressing low to medium levels of CD11b acquire self-renewing stem cell properties and are responsible for the perpetuation of the myeloproliferative phenotype.
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123
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Han Y, Ueno M, Nagahama Y, Takakura N. Identification and characterization of stem cell-specific transcription of PSF1 in spermatogenesis. Biochem Biophys Res Commun 2009; 380:609-13. [DOI: 10.1016/j.bbrc.2009.01.133] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 01/23/2009] [Indexed: 11/29/2022]
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124
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E2A proteins maintain the hematopoietic stem cell pool and promote the maturation of myelolymphoid and myeloerythroid progenitors. Proc Natl Acad Sci U S A 2009; 106:1930-5. [PMID: 19181846 DOI: 10.1073/pnas.0808866106] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hematopoiesis is a tightly controlled process maintained by a small pool of hematopoietic stem cells (HSCs). Here, we demonstrate that the LT-HSC, MPP, premegakaryocytic/erythroid, Pre CFU-E, Pre GM, MkP, and granulocyte-macrophage compartments were all significantly reduced in E2A-deficient bone marrow. Despite a severe depletion of erythroid progenitors, the erythrocyte and megakaryocyte compartments were equivalent in E2A-deficient bone marrow as compared with wild-type mice. E2A-deficient HSCs also failed to efficiently maintain the HSC pool on serial transplantation, and we demonstrate that the E2A proteins regulate cell cycle progression of HSCs by regulating the expression of p21(Cip1), p27(Kip1), and the thrombopoietin receptor, known regulators of HSC self-renewal activity. Based on these observations, we propose that the E2A proteins promote the developmental progression of the entire spectrum of early hematopoietic progenitors and to suppress an erythroid specific program of gene expression in alternative cell lineages. Last, the data mechanistically link E2A, cell cycle regulators, and the maintenance of the HSC pool in a common pathway.
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125
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Distinct roles of stress-activated protein kinases in Fanconi anemia-type C-deficient hematopoiesis. Blood 2009; 113:2655-60. [PMID: 19168785 DOI: 10.1182/blood-2008-09-181420] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The underlying molecular mechanisms that promote bone marrow failure in Fanconi anemia are incompletely understood. Evidence suggests that enhanced apoptosis of hematopoietic precursors is a major contributing factor. Previously, enhanced apoptosis of Fanconi anemia type C-deficient (Fancc(-/-)) progenitors was shown to involve aberrant p38 MAPK activation. Given the importance of c-Jun N-terminal kinase (JNK) in the stress response, we tested whether enhanced apoptosis of Fancc(-/-) cells also involved altered JNK activation. In Fancc(-/-) murine embryonic fibroblasts, tumor necrosis factor alpha (TNF-alpha) induced elevated JNK activity. In addition, JNK inhibition protected Fancc(-/-) murine embryonic fibroblasts and c-kit(+) bone marrow cells from TNF-alpha-induced apoptosis. Importantly, hematopoietic progenitor assays demonstrated that JNK inhibition enhanced Fancc(-/-) colony formation in the presence of TNF-alpha. Competitive repopulation assays showed that Fancc(-/-) donor cells cultured with the JNK inhibitor had equivalent levels of donor chimerism compared with Fancc(-/-) donor cells cultured with vehicle control. In contrast, culturing Fancc(-/-) cells with a p38 MAPK inhibitor significantly increased repopulating ability, supporting an integral role of p38 MAPK in maintaining Fancc(-/-) hematopoietic stem cell function. Taken together, these data suggest that p38 MAPK, but not JNK, has a critical role in maintaining the engraftment of Fancc(-/-)-reconstituting cells under conditions of stress.
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126
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Viatour P, Somervaille TC, Venkatasubrahmanyam S, Kogan S, McLaughlin ME, Weissman IL, Butte AJ, Passegué E, Sage J. Hematopoietic stem cell quiescence is maintained by compound contributions of the retinoblastoma gene family. Cell Stem Cell 2008; 3:416-28. [PMID: 18940733 DOI: 10.1016/j.stem.2008.07.009] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 04/22/2008] [Accepted: 07/16/2008] [Indexed: 12/12/2022]
Abstract
Individual members of the retinoblastoma (Rb) tumor suppressor gene family serve critical roles in the control of cellular proliferation and differentiation, but the extent of their contributions is masked by redundant and compensatory mechanisms. Here we employed a conditional knockout strategy to simultaneously inactivate all three members, Rb, p107, and p130, in adult hematopoietic stem cells (HSCs). Rb family triple knockout (TKO) mice develop a cell-intrinsic myeloproliferation that originates from hyperproliferative early hematopoietic progenitors and is accompanied by increased apoptosis in lymphoid progenitor populations. Loss of quiescence in the TKO HSC pool is associated with an expansion of these mutant stem cells but also with an enhanced mobilization and an impaired reconstitution potential upon transplantation. The presence of a single p107 allele is sufficient to largely rescue these defects. Thus, Rb family members collectively maintain HSC quiescence and the balance between lymphoid and myeloid cell fates in the hematopoietic system.
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Affiliation(s)
- Patrick Viatour
- Department of Pediatrics, Stanford Medical School, Stanford, CA 94305, USA
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127
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A large-scale functional approach to uncover human genes and pathways in Drosophila. Cell Res 2008; 18:1114-27. [PMID: 18957936 DOI: 10.1038/cr.2008.295] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We demonstrate the feasibility of performing a systematic screen for human gene functions in Drosophila by assaying for their ability to induce overexpression phenotypes. Over 1 500 transgenic fly lines corresponding to 236 human genes have been established. In all, 51 lines are capable of eliciting a phenotype suggesting that the human genes are functional. These heterologous genes are functionally relevant as we have found a similar mutant phenotype caused either by a dominant negative mutant form of the human ribosomal protein L8 gene or by RNAi downregulation of the Drosophila RPL8. Significantly, the Drosophila RPL8 mutant can be rescued by wild-type human RPL8. We also provide genetic evidence that Drosophila RPL8 is a new member of the insulin signaling pathway. In summary, the functions of many human genes appear to be highly conserved, and the ability to identify them in Drosophila represents a powerful genetic tool for large-scale analysis of human transcripts in vivo.
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128
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Shima H, Takubo K, Iwasaki H, Yoshihara H, Gomei Y, Hosokawa K, Arai F, Takahashi T, Suda T. Reconstitution activity of hypoxic cultured human cord blood CD34-positive cells in NOG mice. Biochem Biophys Res Commun 2008; 378:467-72. [PMID: 19032938 DOI: 10.1016/j.bbrc.2008.11.056] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2008] [Accepted: 11/14/2008] [Indexed: 10/21/2022]
Abstract
Hematopoietic stem cells (HSCs) reside in hypoxic areas of the bone marrow. However, the role of hypoxia in the maintenance of HSCs has not been fully characterized. We performed xenotransplantation of human cord blood cells cultured in hypoxic or normoxic conditions into adult NOD/SCID/IL-2Rgamma(null) (NOG) mice. Hypoxic culture (1% O(2)) for 6 days efficiently supported the maintenance of HSCs, although cell proliferation was suppressed compared to the normoxic culture. In contrast, hypoxia did not affect in vitro colony-forming ability. Upregulation of a cell cycle inhibitor, p21, was observed in hypoxic culture. Immunohistochemical analysis of recipient bone marrow revealed that engrafted CD34(+)CD38(-) cord blood HSCs were hypoxic. Taken together, these results demonstrate the significance of hypoxia in the maintenance of quiescent human cord blood HSCs.
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Affiliation(s)
- Haruko Shima
- Department of Cell Differentiation, The Sakaguchi Laboratory of Developmental Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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129
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Armesilla-Diaz A, Bragado P, Del Valle I, Cuevas E, Lazaro I, Martin C, Cigudosa JC, Silva A. p53 regulates the self-renewal and differentiation of neural precursors. Neuroscience 2008; 158:1378-89. [PMID: 19038313 DOI: 10.1016/j.neuroscience.2008.10.052] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 10/22/2008] [Accepted: 10/23/2008] [Indexed: 12/25/2022]
Abstract
During embryo neurogenesis, neurons that originate from stem cells located in the forebrain subventricular zone (SVZ) continuously migrate to the olfactory bulb (OB). However, other authors describe the occurrence of resident stem cells in the OB. In the present work we report that the absence of tumor suppressor protein p53 increases the number of neurosphere-forming cells and the proliferation of stem cells derived from 13.5-day embryo OB. Interestingly, differentiation of p53 knockout-derived neurospheres was biased toward neuronal precursors, suggesting a role for p53 in the differentiation process. Moreover, we demonstrate the relevance of p53 in maintaining chromosomal stability in response to genotoxic insult. Finally, our data show that neurosphere stem cells are highly resistant to long-term epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) deprivation in a p53-independent fashion, and they preserve their differentiation potential. Thus, these data demonstrate that p53 controls the proliferation, chromosomal stability and differentiation pattern of embryonic mouse olfactory bulb stem cells.
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Affiliation(s)
- A Armesilla-Diaz
- Department of Cellular and Molecular Physiopathology, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28040 Madrid, Spain
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130
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Liu ZJ, Velazquez OC. Hyperoxia, endothelial progenitor cell mobilization, and diabetic wound healing. Antioxid Redox Signal 2008; 10:1869-82. [PMID: 18627349 PMCID: PMC2638213 DOI: 10.1089/ars.2008.2121] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Diabetic foot disease is a major health problem, which affects 15% of the 200 million patients with diabetes worldwide. Diminished peripheral blood flow and decreased local neovascularization are critical factors that contribute to the delayed or nonhealing wounds in these patients. The correction of impaired local angiogenesis may be a key component in developing therapeutic protocols for treating chronic wounds of the lower extremity and diabetic foot ulcers. Endothelial progenitor cells (EPCs) are the key cellular effectors of postnatal neovascularization and play a central role in wound healing, but their circulating and wound-level numbers are decreased in diabetes, implicating an abnormality in EPC mobilization and homing mechanisms. The deficiency in EPC mobilization is presumably due to impairment of eNOS-NO cascade in bone marrow (BM). Hyperoxia, induced by a clinically relevant hyperbaric oxygen therapy (HBO) protocol, can significantly enhance the mobilization of EPCs from the BM into peripheral blood. However, increased circulating EPCs failed to reach to wound tissues. This is partly a result of downregulated production of SDF-1alpha in local wound lesions with diabetes. Administration of exogenous SDF-1alpha into wounds reversed the EPC homing impairment and, with hyperoxia, synergistically enhanced EPC mobilization, homing, neovascularization, and wound healing.
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Affiliation(s)
- Zhao-Jun Liu
- The DeWitt Daughtry Family Department of Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida 33136, USA
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131
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Abstract
The zinc finger transcription factor GATA-2 has been implicated in the regulation of hematopoietic stem cells. Herein, we explored the role of GATA-2 as a candidate regulator of the hematopoietic progenitor cell compartment. We showed that bone marrow from GATA-2 heterozygote (GATA-2(+/-)) mice displayed attenuated granulocyte-macrophage progenitor function in colony-forming cell (CFC) and serial replating CFC assays. This defect was mapped to the Lin(-)CD117(+)Sca-1(-)CD34(+)CD16/32(high) granulocyte-macrophage progenitor (GMP) compartment of GATA-2(+/-) marrow, which was reduced in size and functionally impaired in CFC assays and competitive transplantation. Similar functional impairments were obtained using a RNA interference approach to stably knockdown GATA-2 in wild-type GMP. Although apoptosis and cell-cycle distribution remained unperturbed in GATA-2(+/-) GMP, quiescent cells from GATA-2(+/-) GMP exhibited altered functionality. Gene expression analysis showed attenuated expression of HES-1 mRNA in GATA-2-deficient GMP. Binding of GATA-2 to the HES-1 locus was detected in the myeloid progenitor cell line 32Dcl3, and enforced expression of HES-1 expression in GATA-2(+/-) GMP rectified the functional defect, suggesting that GATA-2 regulates myeloid progenitor function through HES-1. These data collectively point to GATA-2 as a novel, pivotal determinant of GMP cell fate.
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132
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133
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Banerjee P, Sieburg M, Samuelson E, Feuer G. Human T-cell lymphotropic virus type 1 infection of CD34+ hematopoietic progenitor cells induces cell cycle arrest by modulation of p21(cip1/waf1) and survivin. Stem Cells 2008; 26:3047-58. [PMID: 18818438 DOI: 10.1634/stemcells.2008-0353] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) is an oncogenic retrovirus and the etiologic agent of adult T-cell leukemia (ATL), an aggressive CD4(+) malignancy. HTLV-2 is highly homologous to HTLV-1; however, infection with HTLV-2 has not been associated with lymphoproliferative diseases. Although HTLV-1 infection of CD4(+) lymphocytes induces cellular replication and transformation, infection of CD34(+) human hematopoietic progenitor cells (HPCs) strikingly results in G(0)/G(1) cell cycle arrest and suppression of in vitro clonogenic colony formation by induction of expression of the cdk inhibitor p21(cip1/waf1) (p21) and concurrent repression of survivin. Immature CD34(+)/CD38(-) hematopoietic stem cells (HSCs) were more susceptible to alterations of p21 and survivin expression as a result of HTLV-1 infection, in contrast to more mature CD34(+)/CD38(+) HPCs. Knockdown of p21 expression in HTLV-1-infected CD34(+) HPCs partially abrogated cell cycle arrest. Notably, HTLV-2, an HTLV strain that is not associated with leukemogenesis, does not significantly modulate p21 and survivin expression and does not suppress hematopoiesis from CD34(+) HPCs in vitro. We speculate that the remarkable differences in the activities displayed by CD34(+) HPCs following infection with HTLV-1 or HTLV-2 suggest that HTLV-1 uniquely exploits cell cycle arrest mechanisms to establish a latent infection in hematopoietic progenitor/hematopoietic stem cells and initiates preleukemic events in these cells, which eventually results in the manifestation of ATL.
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Affiliation(s)
- Prabal Banerjee
- Department of Microbiology and Immunology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA
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134
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FoxO3a regulates hematopoietic homeostasis through a negative feedback pathway in conditions of stress or aging. Blood 2008; 112:4485-93. [PMID: 18799725 DOI: 10.1182/blood-2008-05-159848] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Stress or aging of tissue-specific stem cells is considered central to the decline of tissue homeostasis in the elderly, although little is known of molecular mechanisms underlying hematopoietic stem cell (HSC) aging and stress resistance. Here, we report that mice lacking the transcription factor forkhead box O3a (FoxO3a) develop neutrophilia associated with inhibition of the up-regulation of negative regulator of cell proliferation, Sprouty-related Ena/VASP homology 1 domain-containing proteins 2 (Spred2) and AKT and ERK activation, in HSCs during hematopoietic recovery following myelosuppressive stress conditions. Compared with aged wild-type mice, more severe neutrophilia was also observed in aged Foxo3a-deficient mice. AKT and ERK activation and inhibition of Spred2 were detected in HSCs from aged FoxO3a-deficient mice. Spred2-deficient mice also developed neutrophilia during hematopoietic recovery following myelosuppressive stress, indicating that FoxO3a plays a pivotal role in maintenance, integrity, and stress resistance of HSCs through negative feedback pathways for proliferation. This will provide new insight into the hematopoietic homeostasis in conditions of aging and stress.
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135
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Okano H, Sawamoto K. Neural stem cells: involvement in adult neurogenesis and CNS repair. Philos Trans R Soc Lond B Biol Sci 2008; 363:2111-22. [PMID: 18339601 DOI: 10.1098/rstb.2008.2264] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Recent advances in stem cell research, including the selective expansion of neural stem cells (NSCs) in vitro, the induction of particular neural cells from embryonic stem cells in vitro, the identification of NSCs or NSC-like cells in the adult brain and the detection of neurogenesis in the adult brain (adult neurogenesis), have laid the groundwork for the development of novel therapies aimed at inducing regeneration in the damaged central nervous system (CNS). There are two major strategies for inducing regeneration in the damaged CNS: (i) activation of the endogenous regenerative capacity and (ii) cell transplantation therapy. In this review, we summarize the recent findings from our group and others on NSCs, with respect to their role in insult-induced neurogenesis (activation of adult NSCs, proliferation of transit-amplifying cells, migration of neuroblasts and survival and maturation of the newborn neurons), and implications for therapeutic interventions, together with tactics for using cell transplantation therapy to treat the damaged CNS.
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Affiliation(s)
- Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
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136
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Qian Z, Chen L, Fernald AA, Williams BO, Le Beau MM. A critical role for Apc in hematopoietic stem and progenitor cell survival. ACTA ACUST UNITED AC 2008; 205:2163-75. [PMID: 18725524 PMCID: PMC2526209 DOI: 10.1084/jem.20080578] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The adenomatous polyposis coli (Apc) tumor suppressor is involved in the initiation and progression of colorectal cancer via regulation of the Wnt signaling cascade. In addition, Apc plays an important role in multiple cellular functions, including cell migration and adhesion, spindle assembly, and chromosome segregation. However, its role during adult hematopoiesis is unknown. We show that conditional inactivation of Apc in vivo dramatically increases apoptosis and enhances cell cycle entry of hematopoietic stem cells (HSCs)/ hematopoietic progenitor cells (HPCs), leading to their rapid disappearance and bone marrow failure. The defect in HSCs/HPCs caused by Apc ablation is cell autonomous. In addition, we found that loss of Apc leads to exhaustion of the myeloid progenitor pool (common myeloid progenitor, granulocyte-monocyte progenitor, and megakaryocyte-erythroid progenitor), as well as the lymphoid-primed multipotent progenitor pool. Down-regulation of the genes encoding Cdkn1a, Cdkn1b, and Mcl1 occurs after acute Apc excision in candidate HSC populations. Together, our data demonstrate that Apc is essential for HSC and HPC maintenance and survival.
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Affiliation(s)
- Zhijian Qian
- Section of Hematology/Oncology and the Cancer Research Center, University of Chicago, Chicago, IL 60637, USA.
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137
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Wang YY, Yang Y, Chen Q, Yu J, Hou Y, Han L, He J, Jiao D, Yu H. Simultaneous knockdown of p18 INK4C, p27 Kip1and MAD1 via RNA interference results in the expansion of long-term culture-initiating cells of murine bone marrow cells in vitro. Acta Biochim Biophys Sin (Shanghai) 2008. [DOI: 10.1111/j.1745-7270.2008.00448.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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138
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Tothova Z, Gilliland DG. FoxO transcription factors and stem cell homeostasis: insights from the hematopoietic system. Cell Stem Cell 2008; 1:140-52. [PMID: 18371346 DOI: 10.1016/j.stem.2007.07.017] [Citation(s) in RCA: 250] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The forkhead O (FoxO) family of transcription factors participates in diverse physiologic processes, including induction of cell-cycle arrest, stress resistance, differentiation, apoptosis, and metabolism. Several recent studies indicate that FoxO-dependent signaling is required for long-term regenerative potential of the hematopoietic stem cell (HSC) compartment through regulation of HSC response to physiologic oxidative stress, quiescence, and survival. These observations link FoxO function in mammalian systems with the evolutionarily conserved role of FoxO in promotion of stress resistance and longevity in lower phylogenetic systems. Furthermore, these findings have implications for aging in higher organisms and in malignant stem cell biology, and suggest that FoxOs may play an important role in the maintenance and integrity of stem cell compartments in a broad spectrum of tissues.
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Affiliation(s)
- Zuzana Tothova
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
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139
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Kuramitsu M, Hamaguchi I, Takuo M, Masumi A, Momose H, Takizawa K, Mochizuki M, Naito S, Yamaguchi K. Deficient RPS19 protein production induces cell cycle arrest in erythroid progenitor cells. Br J Haematol 2008; 140:348-59. [PMID: 18217898 DOI: 10.1111/j.1365-2141.2007.06930.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The gene encoding ribosomal protein S19 (RPS19) is one of the responsible genes for Diamond-Blackfan anaemia (DBA), a congenital erythroblastopenia. Although haplo-insufficiency of RPS19 has been suggested to be the onset mechanism underlying the pathogenesis of DBA, the sequential mechanism has not been elucidated. In order to analyse the consequences of the missense mutation of RPS19 specific for DBA patients, we made mutated RPS19 expression vectors. Twelve C-terminally Flag-tagged missense mutants were exogenously expressed from retroviral vectors and analysed by Western blot analysis and flow cytometry. When these 12 mutants were expressed in the erythro-leukaemic cell lines K562 and human bone marrow CD34(+) cells, almost all of the mutant proteins (except for G120R) were unstable, and the levels of mutated RPS19 protein were significantly low. To address the effect of deficient RPS19 expression on cell proliferation, RPS19 was downregulated by siRNA. Repressive expression of RPS19 in human CD34(+) cells produced an elevated number of cells at G0 and induced erythroid progenitor-specific defects in BM cells. These results suggest that abnormal ribosomal biogenesis causes inadequate cell cycle arrest in haematopoietic progenitors, and that, subsequently, erythroid progenitors are specifically hampered. These in vitro phenotypes of genetically manipulated CD34(+) cells mimic DBA pathogenesis.
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Affiliation(s)
- Madoka Kuramitsu
- Department of Safety Research on Blood and Biological Products, National Institute of Infectious Disease, Musashimurayama, Tokyo, Japan
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140
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Morales M, Liu Y, Laiakis EC, Morgan WF, Nimer SD, Petrini JHJ. DNA damage signaling in hematopoietic cells: a role for Mre11 complex repair of topoisomerase lesions. Cancer Res 2008; 68:2186-93. [PMID: 18381424 DOI: 10.1158/0008-5472.can-07-2355] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The Mre11 complex promotes DNA double-strand break repair and regulates DNA damage signaling via activation of the ataxia-telangiectasia mutated (ATM) kinase. The hypermorphic Rad50(S) allele encodes a variant of Rad50, a member of the Mre11 complex. Cells expressing Rad50(S) experience constitutive ATM activation, which leads to precipitous apoptotic attrition in hematopoietic cells. In this study, we show that ATM activation by the Rad50S-containing Mre11 complex enhances the proliferation of LSK cells, a population consisting of hematopoietic stem cells and multipotent progenitor cells. In Rad50(S/S) mice, enhanced LSK proliferation triggers apoptotic attrition. This phenotype is mitigated when Rad50(S/S) is combined with mutations that alter either LSK cell quiescence (myeloid elf-1-like factor/ELF4-deficient mice) or hematopoietic differentiation (p21- and p27-deficient mice), indicating that the LSK population is a primary target of Rad50(S) pathology. We show that cells from Rad50(S/S) mice are hypersensitive to camptothecin, a topoisomerase I inhibitor that causes DNA damage primarily during DNA replication. On this basis, we propose that apoptotic attrition of Rad50(S/S) hematopoietic cells results from enhanced proliferation in the context of topoisomerase-associated DNA damage. Impairment of apoptosis in Rad50(S/S) mice promotes hematopoietic malignancy, suggesting that primitive hematopoietic cells serve as a reservoir of potentially oncogenic lesions in Rad50(S/S) mice. These data provide compelling evidence that the Mre11 complex plays a role in the metabolism of topoisomerase lesions in mammals, and further suggest that such lesions can accumulate in primitive hematopoietic cells and confer significant oncogenic potential.
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Affiliation(s)
- Monica Morales
- Molecular Biology Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center and Cornell University Graduate School of Medical Sciences, New York, NY 10021, USA
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141
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Abstract
FoxO transcription factors are an evolutionary conserved subfamily of the forkhead transcription factors, characterized by the forkhead DNA-binding domain. FoxO factors regulate a number of cellular processes involved in cell-fate decisions in a cell-type- and environment-specific manner, including metabolism, differentiation, apoptosis and proliferation. A key mechanism by which FoxO determines cell fate is through regulation of the cell cycle machinery, and as such the cellular consequence of FoxO deregulation is often manifested through perturbation of the cell cycle. Consequently, the deregulation of FoxO factors is implicated in the development of numerous proliferative diseases, in particular cancer.
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142
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Yalcin S, Zhang X, Luciano JP, Mungamuri SK, Marinkovic D, Vercherat C, Sarkar A, Grisotto M, Taneja R, Ghaffari S. Foxo3 is essential for the regulation of ataxia telangiectasia mutated and oxidative stress-mediated homeostasis of hematopoietic stem cells. J Biol Chem 2008; 283:25692-25705. [PMID: 18424439 DOI: 10.1074/jbc.m800517200] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Unchecked accumulation of reactive oxygen species (ROS) compromises maintenance of hematopoietic stem cells. Regulation of ROS by the tumor suppressor protein ataxia telangiectasia mutated (ATM) is critical for preserving the hematopoietic stem cell pool. In this study we demonstrate that the Foxo3 member of the Forkhead Box O (FoxO) family of transcription factors is essential for normal ATM expression. In addition, we show that loss of Foxo3 leads to defects in hematopoietic stem cells, and these defects result from an overaccumulation of ROS. Foxo3 suppression of ROS in hematopoietic stem cells is mediated partly by regulation of ATM expression. We identify ROS-independent modulations of ATM and p16(INK4a) and ROS-mediated activation of p53/p21(CIP1/WAF1/Sdi1) tumor suppressor pathways as major contributors to Foxo3-null hematopoietic stem cells defects. Our studies demonstrate that Foxo3 represses ROS in part via regulation of ATM and that this repression is required for maintenance of the hematopoietic stem cell pool.
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Affiliation(s)
- Safak Yalcin
- Department of Gene and Cell Medicine, New York, New York 10029
| | - Xin Zhang
- Department of Gene and Cell Medicine, New York, New York 10029
| | - Julia P Luciano
- Department of Gene and Cell Medicine, New York, New York 10029
| | | | | | - Cécile Vercherat
- Department of Developmental and Regenerative Biology, New York, New York 10029
| | - Abby Sarkar
- Department of Gene and Cell Medicine, New York, New York 10029
| | - Marcos Grisotto
- Department of Gene and Cell Medicine, New York, New York 10029
| | - Reshma Taneja
- Department of Developmental and Regenerative Biology, New York, New York 10029; Black Family Stem Cell Institute, New York, New York 10029
| | - Saghi Ghaffari
- Department of Gene and Cell Medicine, New York, New York 10029; Department of Developmental and Regenerative Biology, New York, New York 10029; Black Family Stem Cell Institute, New York, New York 10029; Department of Medicine Division of Hematology, Oncology, Mount Sinai School of Medicine, New York, New York 10029.
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143
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Wu W, Kehn-Hall K, Pedati C, Zweier L, Castro I, Klase Z, Dowd CS, Dubrovsky L, Bukrinsky M, Kashanchi F. Drug 9AA reactivates p21/Waf1 and Inhibits HIV-1 progeny formation. Virol J 2008; 5:41. [PMID: 18348731 PMCID: PMC2315641 DOI: 10.1186/1743-422x-5-41] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Accepted: 03/18/2008] [Indexed: 11/26/2022] Open
Abstract
It has been demonstrated that the p53 pathway plays an important role in HIV-1 infection. Previous work from our lab has established a model demonstrating how p53 could become inactivated in HIV-1 infected cells through binding to Tat. Subsequently, p53 was inactivated and lost its ability to transactivate its downstream target gene p21/waf1. P21/waf1 is a well-known cdk inhibitor (CKI) that can lead to cell cycle arrest upon DNA damage. Most recently, the p21/waf1 function was further investigated as a molecular barrier for HIV-1 infection of stem cells. Therefore, we reason that the restoration of the p53 and p21/waf1 pathways could be a possible theraputical arsenal for combating HIV-1 infection. In this current study, we show that a small chemical molecule, 9-aminoacridine (9AA) at low concentrations, could efficiently reactivate p53 pathway and thereby restoring the p21/waf1 function. Further, we show that the 9AA could significantly inhibit virus replication in activated PBMCs, likely through a mechanism of inhibiting the viral replication machinery. A mechanism study reveals that the phosphorylated p53ser15 may be dissociated from binding to HIV-1 Tat protein, thereby activating the p21/waf1 gene. Finally, we also show that the 9AA-activated p21/waf1 is recruited to HIV-1 preintegration complex, through a mechanism yet to be elucidated.
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Affiliation(s)
- Weilin Wu
- The George Washington University Medical Center, Department of Biochemistry and Molecular Biology, Washington, DC 20037, USA.
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144
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Zheng Y, Bie W, Yang R, Perekatt AO, Poole AJ, Tyner AL. Functions of p21 and p27 in the regenerating epithelial linings of the mouse small and large intestine. Cancer Biol Ther 2008; 7:873-9. [PMID: 18344686 DOI: 10.4161/cbt.7.6.5868] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The epithelial linings of the small and large intestine are rapidly turned over and provide an ideal system for exploring links between differentiation and regulation of cell cycle exit. We utilized wild type, p21-/-, p27-/- and p21/p27-/- mice to address contributions of the Cdk inhibitors p21 and p27 to proliferation and differentiation in the mouse gastrointestinal tract. We did not detect any significant differences in proliferation, and all differentiated epithelial cell lineages were represented in all four genotypes. These data indicate that p21 and p27 do not play essential roles in the regulation of normal epithelial renewal in the intestine. These Cdk inhibitors are not needed in vivo for either assembly of Cdk/Cyclin complexes that drive active proliferation, or inhibition of Cdk/Cyclin complexes during cell cycle exit. However, expression of Cyclin D2 and to a lesser degree Cyclin D3 was reduced in p27-/- and p21/p27-/- mice, indicating a unique role for p27 in the regulation of these specific D-type Cyclins in vivo. In the absence of p27, reduced levels of Cyclin D2 and D3 may help to counteract increased proproliferative signals in the intestine.
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Affiliation(s)
- Yu Zheng
- University of Illinois College of Medicine, Department of Biochemistry and Molecular Genetics, Chicago, Illinois 60607, USA
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145
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Macias E, Miliani de Marval PL, Senderowicz A, Cullen J, Rodriguez-Puebla ML. Expression of CDK4 or CDK2 in mouse oral cavity is retained in adult pituitary with distinct effects on tumorigenesis. Cancer Res 2008; 68:162-71. [PMID: 18172308 DOI: 10.1158/0008-5472.can-07-2461] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The keratin 5 (K5) promoter drives transgenic expression to the basal cell layer of stratified epithelia. Surprisingly, analysis of K5CDK4 and K5CDK2 transgenic mouse embryos showed CDK4 and CDK2 expression not only in the expected tissues, but also in the adenohypophysis. This organ is derived from an upwards growth of the primitive oropharynx, a K5-expressing tissue. We show that transgenic expression of CDKs in the embryonic oral ectoderm is specifically retained in undifferentiated cells from the pars intermedia of the adenohypophysis. Interestingly, we found that K5CDK4 mice show a decreased number of pituitary stem cells, even though CDK4 is not expressed in the stem cells but in transit-amplifying (TA)-like cells. Interestingly, CDK4-expressing cells, but not CDK2-expressing cells, strongly synergize with lack of p27(Kip1) to generate pituitary carcinomas that appear with shortened latency and are drastically more aggressive than those arising in p27(-/-) mice. Thus, we show that deregulation of CDK expression in the primitive oral epithelium plays a unique function, providing a selective advantage that gives rise to transgene-positive TA-like pituitary cells. Furthermore, retention of CDK4 in these TA-like pituitary cells synergizes with loss of p27(Kip1) to induce pituitary adenocarcinomas. This model suggests that forced expression of CDK4 sensitizes cells and synergizes with a second change resulting in tumor development.
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Affiliation(s)
- Everardo Macias
- Center for Comparative Medicine and Translational Research, Molecular Biomedical Sciences, North Carolina State University, Raleigh, North Carolina 27606, USA
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146
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Qian H, Buza-Vidas N, Hyland CD, Jensen CT, Antonchuk J, Månsson R, Thoren LA, Ekblom M, Alexander WS, Jacobsen SEW. Critical role of thrombopoietin in maintaining adult quiescent hematopoietic stem cells. Cell Stem Cell 2007; 1:671-84. [PMID: 18371408 DOI: 10.1016/j.stem.2007.10.008] [Citation(s) in RCA: 393] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 09/16/2007] [Accepted: 10/15/2007] [Indexed: 12/12/2022]
Abstract
The role of cytokines in regulation of hematopoietic stem cells (HSCs) remains poorly understood. Herein we demonstrate that thrombopoietin (THPO) and its receptor, MPL, are critically involved in postnatal steady-state HSC maintenance, reflected in a 150-fold reduction of HSCs in adult Thpo(-/-) mice. Further, whereas THPO and MPL proved not required for fetal HSC expansion, HSC expansion posttransplantation was highly MPL and THPO dependent. The distinct role of THPO in postnatal HSC maintenance is accompanied by accelerated HSC cell-cycle kinetics in Thpo(-/-) mice and reduced expression of the cyclin-dependent kinase inhibitors p57(Kip2) and p19(INK4D) as well as multiple Hox transcription factors. Although also predicted to be an HSC viability factor, BCL2 failed to rescue the HSC deficiency of Thpo(-/-) mice. Thus, THPO regulates posttransplantation HSC expansion as well as the maintenance of adult quiescent HSCs, of critical importance to avoid postnatal HSC exhaustion.
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Affiliation(s)
- Hong Qian
- Hematopoietic Stem Cell Laboratory, Lund Strategic Research Center for Stem Cell Biology and Cell Therapy, Lund University, 221 84, Sweden
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147
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Rosu-Myles M, Taylor BJ, Wolff L. Loss of the tumor suppressor p15Ink4b enhances myeloid progenitor formation from common myeloid progenitors. Exp Hematol 2007; 35:394-406. [PMID: 17309820 DOI: 10.1016/j.exphem.2006.11.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Revised: 11/06/2006] [Accepted: 11/08/2006] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The tumor suppressor p15Ink4b (Ink4b) is a cell-cycle inhibitor that is inactivated in a high percentage of acute myeloid leukemia and myeloid dysplasia syndrome cases. Despite this, the role of Ink4b in hematopoiesis remains unclear. Here we examined the role of Ink4b in blood cell formation using Ink4b-deficient (Ink4b(-/-)) mice. METHODS We compared the bone marrow (BM) of Ink4b(-/-) and wild-type mice using flow cytometric, colony-forming unit and competitive repopulating assays (CRA). The proliferation, differentiation, self-renewal, and apoptosis of progenitor cells were further compared by in vitro and in vivo methods. RESULTS BM from Ink4b(-/-) mice contained increased numbers of granulocyte-monocyte progenitors and Gr-1(+) cells and showed a competitive advantage over wild-type cells in myeloid cell formation by CRA. Ink4b(-/-) progenitors did not demonstrate increased proliferation, self-renewing potential, or reduced apoptosis. Instead, Ink4b(-/-) common myeloid progenitors (CMPs) showed increased myeloid progenitor formation concomitant with reduced erythroid potential. CONCLUSIONS This work establishes a role for Ink4b in regulating the differentiation of CMPs and indicates that loss of Ink4b enhances the formation of myeloid progenitors.
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Affiliation(s)
- Michael Rosu-Myles
- Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892-4263, USA
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148
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Abstract
Stem cell research is at the heart of regenerative medicine, which holds great promise for the treatment of many devastating disorders. However, in addition to hurdles posed by well-publicized ethical issues, this emerging field presents many biological challenges. What is a stem cell? How are embryonic stem cells different from adult stem cells? What are the physiological bases for therapeutically acceptable stem cells? In this editorial review, I will briefly discuss these superficially simple but actually rather complex issues that surround this fascinating cell type. The goal of this special issue on stem cells in Gene Therapy is to review some fundamental and critical aspects of current stem cell research that have translational potential.
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149
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The retinoblastoma tumor suppressor is a critical intrinsic regulator for hematopoietic stem and progenitor cells under stress. Blood 2007; 111:1894-902. [PMID: 18048646 DOI: 10.1182/blood-2007-02-071746] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The retinoblastoma tumor suppressor protein (RB) plays important roles in the control of the cell division cycle. It is estimated that RB is dysfunctional/inactivated in up to 40% of human leukemias. The consequences of loss of RB on hematopoietic stem and progenitor cell (HSPC) function in vivo are incompletely understood. Here, we report that mice genetically deficient in Rb in all hematopoietic cells (Vav-Cre Rb knockout [KO] animals) showed altered contribution of distinct hematopoietic cell lineages to peripheral blood, bone marrow, and spleen; significantly increased extramedullary hematopoiesis in the spleen; and a 2-fold increase in the frequency of hematopoietic progenitor cells in peripheral blood. Upon competitive transplantation, HSPCs from Vav-Cre Rb KO mice contributed with an at least 4- to 6-fold less efficiency to hematopoiesis compared with control cells. HSPCs deficient in Rb presented with impaired cell-cycle exit upon stress-induced proliferation, which correlated with impaired function. In summary, Rb is critical for hematopoietic stem and progenitor cell function, localization, and differentiation.
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150
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Abstract
Adult stem cells have become the focus of intense research in recent years as a result of their role in the maintenance and repair of tissues. They exert this function through their extensive expansion (self-renewal) and multipotent differentiation capacity. Understanding whether adult stem cells retain this capacity throughout the lifespan of the individual, or undergo a process of ageing resulting in a decreased stem cell pool, is an important area of investigation. Progress in this area has been hampered by lack of suitable models and of appropriate markers and assays to identify stem cells. However, recent data suggest that an understanding of the mechanisms governing stem cell ageing can give insight into the mechanism of tissue ageing and, most importantly, advance our ability to use stem cells in cell and gene therapy strategies.
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