Haploinsufficiency Of SAMD9L, An Endosome Fusion Facilitator, In Mice Induces The Development Of Myeloid Malignancies Mimicking Human Diseases With Monosomy 7

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 227-227
Author(s):  
Hirotaka Matsui ◽  
Akiko Nagamachi ◽  
Akinori Kanai ◽  
Yuko Ozaki ◽  
Hiroaki Honda ◽  
...  
Keyword(s):  
Stem Cells ◽  
Progenitor Cells ◽  
Myeloid Leukemia ◽  
Early Endosome ◽  
Cytokine Receptors ◽  
Juvenile Myelomonocytic Leukemia ◽  
Self Renewal ◽  
Newborn Mice ◽  
Monosomy 7 ◽  
Deficient Mice

Abstract Monosomy 7 is a common chromosomal abnormality found frequently in MDS and AML. We previously identified a common microdeletion cluster in 7q21.3 in juvenile myelomonocytic leukemia patients. This cluster contains three poorly characterized genes: sterile alpha motif (SAM) domain-9 (SAMD9) which is absent in mice, samd9-like (SAMD9L) and Miki (LOC253012). Although mutations have rarely been seen in these genes, the genes reside proximal to the 7q22 band that is deleted in single copy in nearly 25% of AML and MDS patients. We recently reported that Miki, a centrosomal protein that promotes alignment of chromosomes at metaphase, is a candidate gene responsible for mitotic/nuclear abnormalities observed in MDS patients (Mol Cell 2012). In this study, we established and characterized SAMD9L-deficient mice, along with the analysis of molecular function of SAMD9L protein. Among SAMD9L-/- (n=15) and SAMD9L+/- (n=15) littermates, 13 mice developed myeloid dysplasia, 2 mice developed myeloid leukemia and one mouse developed myeloproliferative disease after the age of 18 months, while all but one SAMD9L+/+ mice (n=23) maintained normal hematopoiesis throughout the 24-month observation period. Infection of MOL4070A retrovirus into newborn mice developed myeloid leukemia within 15 months preferentially in SAMD9L-deficient genetic background with Evi1 and Fbxl10 (encoding a H3K36 demethylase) genes as common virus integration sites. While bone marrow (BM) cells from SAMD9L+/+ mice (12 weeks old) formed fewer colonies by the third replating, cells from SAMD9L-deficient mice continued to form similar numbers and sizes of well-differentiated colonies beyond the 7th plating. The excess number of colonies formed was reduced by retrovirus-mediated forced expression of Samd9L. These data suggested enhanced self-renewal and/or delays in differentiation of SAMD9L-deficient stem cells. In addition, enhanced reconstitution ability of SAMD9L-deficient stem cells was demonstrated by competitive repopulation assay using the Ly5 congenic mouse system, where irradiated Ly5.1 mice were transplanted with long term-LSK cells from SAMD9L+/+ or SAMD9L-deficient Ly5.2 mice (10 weeks old) together with BM cells from SAMD9L+/+Ly5.1 mice. This was confirmed by limiting-dilution transplants, results of which showed a higher frequency of multi-lineage repopulating cells at 8 weeks in SAMD9L-/- donor BM. Moreover, growth advantage in the presence of cytokines was evident in liquid cultures of SAMD9L-deficient BM progenitor cells. Hypersensitivity of SAMD9L-deficient BM progenitors to cytokines was also shown in in vivo experiments, in which SAMD9L-deficient mice injected with cyclophosphamide (day 0) and G-CSF (days 1-4) showed significantly higher WBC counts than SAMD9L+/+ mice at the nadir (day 3). These findings suggested that SAMD9L-deficiency sensitizes hematopoietic progenitors to cytokines. Immunostaining using SAMD9L antibody showed a vesicular pattern of SAMD9L localization in approximately 15% of BM progenitor cells that overlapped with the localization of EEA1, an early endosomal protein. In SAMD9L-/- fibroblasts, while rapid endocytosis of PDGF-receptor (PDGFR) by PDGF stimulation occurred in a time-course similar to that in SAMD9L+/+ cells, homotypic fusion of endosomes containing PDGFR delayed. Inhibition of endosome fusion in SAMD9L-/- cells lead to the accumulation of PDGFR that were remained to be phosphorylated in early endosome, resulting in the prolonged activation of cytokine signals. Accumulation of cytokine receptors in early endosome and persistent cytokine signals were also found in BM progenitors obtained from SAMD9L-deficient mice. These observations suggest that SAMD9L is a crucial component of a protein complex that facilitates the degradation of cytokine receptors through the homotypic fusion of endosomes. Collectively, our study suggests the contribution of haploinsufficiency of SAMD9L to the pathogenesis of myeloid diseases harboring -7/7q- through the prolonged activation of cytokine signals that results in the enhancement of stem cell self-renewal and/or delay in differentiation of early progenitors. Deletion of other haploinsufficient tumor-suppressor genes that reside in 7q would collaborate with the deficiency of SAMD9L for myeloid leukemogenesis. Disclosures: No relevant conflicts of interest to declare.

Expression of the CAMPATH-1 Antigen (CD52) on CD34+/CD38- Progenitor Cells in Patients with 5q- MDS and in a Subset of AML

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1728-1728
Author(s):  
Katharina Blatt ◽  
Harald Herrmann ◽  
Sabine Cerny-Reiterer ◽  
Susanne Herndlhofer ◽  
Wolfgang R. Sperr ◽  
...  
Keyword(s):  
Stem Cells ◽  
Progenitor Cells ◽  
Myeloid Leukemia ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasms ◽  
Lymphocytic Leukemia ◽  
Target Antigen ◽  
Blood Monocytes ◽  
Trisomy 8 ◽  
Monosomy 7

Abstract Abstract 1728 The target antigen CAMPATH-1 (CD52) is widely expressed in various hematopoietic lineages inlcuding lymphocytes, basophils, and blood monocytes. The anti-CD52 antibody Alemtuzumab is used successfully to treat patients with chemotherapy-refractory chronic lymphocytic leukemia. Based on its strong immunosuppressive effects, Alemtuzumab has also been considered for patients with aplastic anemia and hypoplastic myelodysplastic syndromes (MDS). Indeed, more recently, Alemtuzumab was found to induce major hematologic responses in a group of patients with MDS. Although the immunosuppressive effect was considered to play a role, the exact mechanisms underlying this drug effect remained speculative. In the current study, we asked whether CD34+ bone marrow (BM) progenitor cells in MDS and acute myeloid leukemia (AML) express the CAMPATH-1 antigen. Twelve patients with MDS (5 females, 7 males; median age: 70 years), 25 patients with AML (16 females, 9 males; median age: 62 years), and 34 control cases (normal reactive BM, n=12; idiopathic cytopenia of unknown significance, n=11; chronic myeloid leukemia, CML, n=4; chronic myelomonocytic leukemia, CMML, n=3; JAK2 V617F+ myeloproliferative neoplasms, MPN, n=4) were examined. Surface expression of CD52 on CD34+/CD38+ and CD34+/CD38- BM progenitor cells was analyzed by monoclonal antibodies and multicolor flow cytometry. In the group of MDS, CD52 was detectable on CD34+/CD38- stem cells in 3/4 patients with isolated 5q-. In most of the other MDS patients, CD52 was weakly expressed or not detectable on CD34+/CD38- cells. In AML, CD34+/CD38- cells displayed CD52 in 12/25 patients, namely 3 with complex karyotype including 5q-, 2 with inv(3), one with t(8;21), one with inv(16), one with del13q, one with trisomy 8, one with monosomy 7, and 2 with normal karyotype. Expression of CD52 mRNA in CD34+/CD38- AML stem cells was confirmed by qPCR in all patients tested (n=14). In addition, a good correlation was found between surface CD52 expression and CD52 mRNA expression in AML progenitor fractions. In patients with normal hematopoiesis (n=12) or idiopathic cytopenia (n=11), CD34+/CD38- cells stained weakly positive or negative for CD52. Almost in all cases tested, blood monocytes and blood basophils stained positive for CD52. Together, our data suggest that the target antigen CAMPATH-1 (CD52) is expressed on primitive CD34+/CD38- progenitor cells in MDS, preferentially in 5q- patients, and in a subset of patients with AML. These observations may have clinical implications and explain recently described effects of Alemtuzumab in patients with MDS. Our data also suggest that Alemtuzumab may be an interesting targeted drug in patients with refractory or relapsed AML in whom neoplastic stem cells express the target antigen CD52. Disclosures: No relevant conflicts of interest to declare.

Samd9L-Deficient Mice Develop Myeloid Malignancies Mimicking Human Diseases with Monosomy 7

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 869-869
Author(s):  
Hirotaka Matsui ◽  
Akiko Nagamachi ◽  
Yuko Ozaki ◽  
Hiroya Asou ◽  
Hiroaki Honda ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Myeloid Leukemia ◽  
Bone Marrow Cells ◽  
Human Diseases ◽  
Newborn Mice ◽  
Monosomy 7 ◽  
Myeloid Malignancies ◽  
Myeloid Neoplasms ◽  
Deficient Mice ◽  
Marrow Cells

Abstract Abstract 869 Monosomy 7 is a common chromosomal abnormality found frequently in MDS and AML. We previously identified a common microdeletion cluster in subband 7q21.3 in JMML patients (Asou et al., 2009). This cluster contains three poorly characterized genes: sterile alpha motif (SAM) domain-9 (Samd9) which is absent in mice, Samd9-like (Samd9L) and Miki (LOC253012). In this study we established and characterized Samd9L-deficient mice in detail and found that these mice develop myeloid malignancies that mimic human diseases with −7/7q-. Samd9L −/− (n=10), Samd9L+/− (n=11) and Samd9L+/+ (n=13) littermates were observed for signs of illness for 2 years. All but one Samd9L+/+ mice maintained consistent WBC counts and hemoglobin levels throughout the observation period. Meanwhile, seven among 21 Samd9L+/− and Samd9L−/− mice developed neutropenia and/or anemia and 2 mice showed an apparent WBC increase after the age of 18 months. Based on Bethesda proposals for classification, the types and frequencies of myeloid diseases demonstrated by mice included myeloid dysplasia (5/10 Samd9L−/−; 2/11 Samd9L+/−), myeloid leukemia (1/10 Samd9L−/−; 1/11 Samd9L+/−) and myeloproliferative disease (1/11 Samd9L+/−). To determine whether loss of the Samd9L gene predisposes mice to myeloid diseases, newborn mice were injected with MOL4070A retrovirus which selectively induces AML or MDS in mice with propensity to myeloid malignancies. There was a significant effect, in that almost all Samd9L+/− (12/14) and Samd9L−/− (10/12) mice died from myeloid neoplasms, roughly one year earlier than mice that developed spontaneous myeloid malignancies without retroviral infection. In contrast, only 2 of 30 MOL4070A-infected Samd9L+/+ mice developed myeloid diseases. Unlike uninfected Samd9L+/− and Samd9L−/− mice, which preferentially developed MDS (7/21), 16 of 26 virus-infected mice showed myeloid leukemias of various subtypes including undifferentiated, myelomonocytic, or monocytic leukemia that expressed combinations of surface markers for the granulocytic, monocytic, erythroid or megakaryocytic lineage. By applying inverse PCR method, two common retrovirus integration sites, Evi1 and Fbxl10 genes, were identified in leukemic samples specifically from Samd9L−/− and Samd9L+/− mice. The enhanced incidence of leukemia in mice with Samd9L-deficiency by Evi1 or Fbxl10 overexpression was further analyzed by transplanting Samd9L−/− or Samd9L+/+ bone marrow cells transduced with retrovirus expressing Evi1 or Fbxl10. All mice (11/11) receiving transferred Samd9L−/−Evi1 bone marrow cells died from hematopoietic malignancies, particularly myeloid disorders (10/11). While not a statistically significant result, we also found that three of 13 mice receiving transferred Samd9L −/−Fbxl10 bone marrow cells developed myeloid malignancies. The development of MDS in Samd9L+/− and Samd9L−/− mice of advancing age mimics the typical clinical association between −7/7q- and sporadic MDS in elderly humans, while development of wide-variety of myeloid leukemia subtypes in retrovirus-infected Samd9L+/− and Samd9L−/− mice indicates that Samd9L gene-deficiency can promote diverse leukemogenic pathways, mimicking another clinical feature of −7/7q-: i.e., deep involvement in therapy-related AML/MDS as well as AML/MDS among patients with a propensity for myeloid diseases. As we reported last year, Samd9L protein localizes to the early endosome. Cells expressing Samd9L at low levels internalize ligand-bound cytokine receptors normally, but there is a delay in homotypic fusion of endosomes that results in prolonged cellular activation to cytokine signals. Moreover, colony replating assay revealed that Samd9L+/− and Samd9L−/− bone marrow cells maintain colony forming ability beyond 7th plating. Although detailed mechanisms remain to be elucidated, we hypothesize that excess cytokine-receptor signaling due to Samd9/Samd9L insufficiency induces self-renewal of hematopoietic stem cells and/or delays in differentiation of early progenitors, resulting in the development of myeloid neoplasms in cooperation with genetic and age-related epigenetic alterations. Disclosures: No relevant conflicts of interest to declare.

KLF4 Regulates Self-Renewal of Leukemic Stem Cells in Chronic Myeloid Leukemia By Repressing Gbl Expression and Altering mTORC2 Activity

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1789-1789
Author(s):  
Chun Shik Park ◽  
Ye Shen ◽  
Takeshi Yamada ◽  
Koramit Suppipat ◽  
Monica Puppi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Chronic Myeloid Leukemia ◽  
Progenitor Cells ◽  
Myeloid Leukemia ◽  
Conflicts Of Interest ◽  
Chronic Phase ◽  
Leukemic Stem Cells ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Tyrosine kinase inhibitors (TKIs) are the standard treatment for eradicating BCR-ABL-positive progenitor cells in chronic myeloid leukemia (CML); however, disease often relapses upon drug discontinuation because TKIs do not effectively eliminate leukemic stem cells (LSC). The development of novel strategies aimed at eradicating LSC without harming normal hematopoietic stem cells (HSC) is essential for the cure of CML patients. The generation of LSC-directed therapy relies on the identification of novel molecular pathways that selectively regulate LSC function independent of BCR-ABL. The Krüppel-like factor 4(KLF4) is a transcription factor that can either activate or repress gene transcription acting as an oncogene or a tumor suppressor depending on the cellular context. Analysis of a published dataset from chronic phase CML patients revealed elevated levels of KLF4 in LSC compared to progenitor cells indicating that KLF4 is likely implicated in LSC regulation. To study the role of KLF4 in LSC function, we used a CML mouse model combining somatic deletion of the Klf4 gene and retroviral transduction and transplantation of HSC. In contrast to mice receiving BCR-ABL-transduced Klf4fl/fl HSC that developed and succumbed to CML, mice transplanted with BCR-ABL-transduced Klf4Δ/Δ (Klf4fl/fl Vav-iCre+) HSC showed a progressive loss of leukemia despite an initial expansion of myeloid leukemic cells, which led to increased overall survival. This inability to sustain CML in the absence of KLF4 was caused by attrition of LSC in bone marrow and the spleen. Furthermore, deletion of KLF4 impaired the ability of LSC to recapitulate leukemia in secondary recipients suggesting a loss of self-renewal capacity. In contrast to LSC, KLF4 deletion led to increased self-renewal of normal HSC assessed by serial competitive transplantation. To identify KLF4 target genes involved in LSC self-renewal, we performed a global gene expression analysis using Klf4Δ/Δ LSC purified by cell sorting from leukemic mice. Analysis of gene expression in Klf4Δ/Δ LSC revealed significant upregulation of GβL, a component of mTOR complexes. Finally, we identified that KLF4 binds to GβL promoter by Chip-Seq analysis and that silencing resulted in inhibition of mTORC2 but not mTORC1 activity in 32D-BCR-ABL-positive CML cells. Our findings suggest that KLF4 transcriptionally represses GβL expression in LSC and that mTORC2 inhibition has the potential to completely eradicate LSC and induce treatment-free remission. Disclosures No relevant conflicts of interest to declare.

Titan (Samd9L), a Candidate -7/7q- Responsible Gene Product, Downregulates Cytokine Signals by Facilitating Formation of Early Endosomes

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4170-4170
Author(s):  
Hirotaka Matsui ◽  
Akiko Nagamachi ◽  
Yuko Ozaki ◽  
Hiroya Asou ◽  
Hiroaki Honda ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Myeloid Leukemia ◽  
Bone Marrow Cells ◽  
Early Endosome ◽  
Cytokine Receptors ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Pdgf Stimulation ◽  
Intracellular Vesicles ◽  
Deficient Mice

Abstract Abstract 4170 We previously isolated Titan (=Samd9L) and Kasumi (=Samd9) as candidate responsible genes for 7q deletion in AML/MDS, from a common microdeletion cluster we identified in chromosome subband 7q21.3 in childhood myeloid leukemia (ASH abstract 2008). Titan and Kasumi are paralogous genes that encode 60% identical proteins with unknown function. We generated Titan deficient mice (mouse genome contains only Titan gene and lacks Kasumi gene) and found that haploinsufficiency of Titan promotes myeloid leukemogenesis (ASH abstracts 2008 & 2009). Briefly, although Titan-deficient mice were born and grown normally without hematological abnormalities, half of both heterozygous (Titan +/−) and homozygous (Titan -/-) mice naturally developed myeloid leukemia in their advanced age. By applying retroviral insertional mutagenesis, we identified co-operative genes, Evi1 and Fbxl10 (encoding H3K4 histone demethylase), that accelerate leukemia development by aberrant over-expression. Contributions of Evi1 and Fbxl10 to leukemogenesis were confirmed by mouse BMT experiments using Titan -/- and +/+ bone marrow cells retrovirally transduced with Evi1 or Fbxl10. In this presentation, we report molecular mechanisms through which Titan suppresses myeloid leukemogenesis. Immunofluorescence staining revealed cytoplasmic localization of endogenous Titan protein as a vesicular pattern that partially overlapped with EEA1, an early endosomal protein. EEA1 was also found as a Titan-binding protein by immunoprecipitation analysis, suggesting that Titan is involved in the regulation of endosome function such as degradation of cytokine receptors. We initially analyzed lung fibroblasts that express Titan at high levels and have wide cytoplasm allowing detailed observation of endosomes. In Titan +/+ fibroblasts, PDGF receptors (PDGFR) were incorporated into intracellular vesicles within 15 min after stimulation with PDGF. The long span of each endosome increased more than 1.5 μm and converted to late endosomes to form lysosomes within 30 min. By contrast, in Titan +/− and -/- fibroblasts, although rapid internalization of PDGFR occurred in a time-course similar to that in Titan +/+ cells, homotypic fusion of PDGFR-containing vesicles seemed to be inhibited, which was shown by the persistence of small intracellular vesicles after PDGF stimulation. Because fusion of vesicles into early endosome is an essential step for sorting endocytosed cytokine receptors toward degradation in lysosomes, we hypothesized that deficiency of Titan may induce defects in the degradation of cytokine receptors. We labeled cell surface proteins with cell-impermeable biotin carrying a disulfide bond, and then cells were stimulated with PDGF. After biotin-labeled PDGFR are incorporated into intracellular vesicles, residual cell surface biotin was removed by the addition of reducing agent (MESNA). Cells were lysed and incorporated (biotinylated) PDGFR were precipitated using streptavidin beads and were detected by immunoblotting. This experiment showed that PDGFR accumulated in intracellular fraction after PDGF stimulation in Titan +/− and -/- cells but not in Titan +/+ cells. Moreover, endocytosed PDGFR were remained to be phosphorylated at Tyr1009 site, suggesting that they are kept activated in endosomes. This is consistent with the finding that sustained activation of Akt after PDGF stimulation was seen in Titan +/− and -/- cells. Persistent cytokine signals were also found in Baf-3 (IL-3-dependent hematopoietic) cells expressing Titan at reduced levels by constitutively expressing short hairpin (sh) RNA specific for Titan mRNA. Although IL-3 receptor α were rapidly endocytosed in Titan-downregulated cells after IL-3 stimulation, IL-3 receptors accumulated in endosomal fraction, resulting in prolonged ERK activation. Furthermore, bone marrow cells obtained from Titan -/- and +/− mice were hyper-responsible to cytokines, resulting in sustained colony forming activity after several times of re-plating. Overall, these results suggest that Titan negatively regulates cytokine signaling through the promotion of receptor degradation via maturation of early endosome to late endosomes/lysosomes through fusion of early endosomes and that deficiency of Titan contributes to myeloid leukemogenesis in collaboration with other genetical or epi-genetical gene alterations, such as overexpression of Evi-1. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Liver X receptor β regulates the development of the dentate gyrus and autistic-like behavior in the mouse

2018 ◽  
Vol 115 (12) ◽  
pp. E2725-E2733 ◽  
Author(s):  
Yulong Cai ◽  
Xiaotong Tang ◽  
Xi Chen ◽  
Xin Li ◽  
Ying Wang ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Progenitor Cells ◽  
Progenitor Cell ◽  
Neural Progenitor Cells ◽  
Repetitive Behavior ◽  
Autism Spectrum ◽  
Liver X Receptor ◽  
Self Renewal ◽  
Spectrum Disorders ◽  
Deficient Mice

The dentate gyrus (DG) of the hippocampus is a laminated brain region in which neurogenesis begins during early embryonic development and continues until adulthood. Recent studies have implicated that defects in the neurogenesis of the DG seem to be involved in the genesis of autism spectrum disorders (ASD)-like behaviors. Liver X receptor β (LXRβ) has recently emerged as an important transcription factor involved in the development of laminated CNS structures, but little is known about its role in the development of the DG. Here, we show that deletion of the LXRβ in mice causes hypoplasia in the DG, including abnormalities in the formation of progenitor cells and granule cell differentiation. We also found that expression of Notch1, a central mediator of progenitor cell self-renewal, is reduced in LXRβ-null mice. In addition, LXRβ deletion in mice results in autistic-like behaviors, including abnormal social interaction and repetitive behavior. These data reveal a central role for LXRβ in orchestrating the timely differentiation of neural progenitor cells within the DG, thereby providing a likely explanation for its association with the genesis of autism-related behaviors in LXRβ-deficient mice.

scholarly journals Identification of BCR/ABL-negative primitive hematopoietic progenitor cells within chronic myeloid leukemia marrow

Blood ◽  
1993 ◽  
Vol 81 (3) ◽  
pp. 801-807 ◽  
Author(s):  
T Leemhuis ◽  
D Leibowitz ◽  
G Cox ◽  
R Silver ◽  
EF Srour ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Chronic Myeloid Leukemia ◽  
Progenitor Cells ◽  
Myeloid Leukemia ◽  
Chronic Phase ◽  
Polymerase Chain Reaction Analysis ◽  
Hematopoietic Progenitor Cells ◽  
Hematopoietic Progenitor ◽  
Hematopoietic Stem

Chronic myeloid leukemia (CML) is a malignant disorder of the hematopoietic stem cell. It has been shown that normal stem cells coexist with malignant stem cells in the bone marrow of patients with chronic-phase CML. To characterize the primitive hematopoietic progenitor cells within CML marrow, CD34+DR- and CD34+DR+ cells were isolated using centrifugal elutriation, monoclonal antibody labeling, and flow cytometric cell sorting. Polymerase chain reaction analysis of RNA samples from these CD34+ subpopulations was used to detect the presence of the BCR/ABL translocation characteristic of CML. The CD34+DR+ subpopulation contained BCR/ABL(+) cells in 11 of 12 marrow samples studied, whereas the CD34+DR- subpopulation contained BCR/ABL(+) cells in 6 of 9 CML marrow specimens. These cell populations were assayed for hematopoietic progenitor cells, and individual hematopoietic colonies were analyzed by PCR for their BCR/ABL status. Results from six patients showed that nearly half of the myeloid colonies cloned from CD34+DR- cells were BCR/ABL(+), although the CD34+DR- subpopulation contained significantly fewer BCR/ABL(+) progenitor cells than either low-density bone marrow (LDBM) or the CD34+DR+ fraction. These CD34+ cells were also used to establish stromal cell-free long-term bone marrow cultures to assess the BCR/ABL status of hematopoietic stem cells within these CML marrow populations. After 28 days in culture, three of five cultures initiated with CD34+DR- cells produced BCR/ABL(-) cells. By contrast, only one of eight cultures initiated with CD34+DR+ cells were BCR/ABL(-) after 28 days. These results indicate that the CD34+DR- subpopulation of CML marrow still contains leukemic progenitor cells, although to a lesser extent than either LDBM or CD34+DR+ cells.

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.

scholarly journals Mouse acute leukemia develops independent of self-renewal and differentiation potentials in hematopoietic stem and progenitor cells

2019 ◽  
Vol 3 (3) ◽  
pp. 419-431 ◽  
Author(s):  
Fang Dong ◽  
Haitao Bai ◽  
Xiaofang Wang ◽  
Shanshan Zhang ◽  
Zhao Wang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Leukemia ◽  
Progenitor Cells ◽  
Lymphoblastic Leukemia ◽  
The Self ◽  
Myelogenous Leukemia ◽  
Mouse Bone Marrow ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells

Abstract The cell of origin, defined as the normal cell in which the transformation event first occurs, is poorly identified in leukemia, despite its importance in understanding of leukemogenesis and improving leukemia therapy. Although hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) were used for leukemia models, whether their self-renewal and differentiation potentials influence the initiation and development of leukemia is largely unknown. In this study, the self-renewal and differentiation potentials in 2 distinct types of HSCs (HSC1 [CD150+CD41−CD34−Lineage−Sca-1+c-Kit+ cells] and HSC2 [CD150−CD41−CD34−Lineage−Sca-1+c-Kit+ cells]) and 3 distinct types of HPCs (HPC1 [CD150+CD41+CD34−Lineage−Sca-1+c-Kit+ cells], HPC2 [CD150+CD41+CD34+Lineage−Sca-1+c-Kit+ cells], and HPC3 [CD150−CD41−CD34+Lineage−Sca-1+c-Kit+ cells]) were isolated from adult mouse bone marrow, and examined by competitive repopulation assay. Then, cells from each population were retrovirally transduced to initiate MLL-AF9 acute myelogenous leukemia (AML) and the intracellular domain of NOTCH-1 T-cell acute lymphoblastic leukemia (T-ALL). AML and T-ALL similarly developed from all HSC and HPC populations, suggesting multiple cellular origins of leukemia. New leukemic stem cells (LSCs) were also identified in these AML and T-ALL models. Notably, switching between immunophenotypical immature and mature LSCs was observed, suggesting that heterogeneous LSCs play a role in the expansion and maintenance of leukemia. Based on this mouse model study, we propose that acute leukemia arises from multiple cells of origin independent of the self-renewal and differentiation potentials in hematopoietic stem and progenitor cells and is amplified by LSC switchover.

scholarly journals microRNA-29a induces aberrant self-renewal capacity in hematopoietic progenitors, biased myeloid development, and acute myeloid leukemia

2010 ◽  
Vol 207 (3) ◽  
pp. 475-489 ◽  
Author(s):  
Yoon-Chi Han ◽  
Christopher Y. Park ◽  
Govind Bhagat ◽  
Jinping Zhang ◽  
Yulei Wang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Ectopic Expression ◽  
Hematopoietic Progenitors ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Myeloid Development ◽  
Acute Myeloid ◽  
Myeloid Progenitors

The function of microRNAs (miRNAs) in hematopoietic stem cells (HSCs), committed progenitors, and leukemia stem cells (LSCs) is poorly understood. We show that miR-29a is highly expressed in HSC and down-regulated in hematopoietic progenitors. Ectopic expression of miR-29a in mouse HSC/progenitors results in acquisition of self-renewal capacity by myeloid progenitors, biased myeloid differentiation, and the development of a myeloproliferative disorder that progresses to acute myeloid leukemia (AML). miR-29a promotes progenitor proliferation by expediting G1 to S/G2 cell cycle transitions. miR-29a is overexpressed in human AML and, like human LSC, miR-29a-expressing myeloid progenitors serially transplant AML. Our data indicate that miR-29a regulates early hematopoiesis and suggest that miR-29a initiates AML by converting myeloid progenitors into self-renewing LSC.

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