Endogenous Nras G12D/+ and G12D/G12D Distinctly Regulate Self-Renewal and Differentiation of Haematopoietic Stem Cells

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4086-4086
Author(s):  
Guangyao Kong ◽  
Jinyong Wang ◽  
Yangang Liu ◽  
Juan Du ◽  
Alisa Damnernsawad ◽  
...  
Keyword(s):  
Stem Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Myeloproliferative Neoplasm ◽  
Erk Signaling ◽  
Dependent Manner ◽  
Self Renewal ◽  
Haematopoietic Stem Cells ◽  
Leukemia Development ◽  
Dose Dependent

Abstract Abstract 4086 How oncogenes regulate adult stem cells to promote tumorigenesis is poorly understood. We and others previously reported that recipient mice transplanted with Nras G12D/+ or Nras G12D/G12D bone marrow cells develop distinct haemtopoietic malignancies. Mice with G12D/+ cells predominantly develop a myeloproliferative neoplasm (MPN) closely resembling chronic myelomonocytic leukemia (CMML), while animals with G12D/G12D cells develop acute T- or B-cell lymphoblastic leukemia (TALL or BALL) and/or MPN, with varying penetrance, which appear to be regulated by the activity of G12D/G12D haematopoietic stem cells (HSCs). Consistent with this notion, we found that G12D/+ HSCs are required to initiate and maintain CMML-like phenotypes in recipient mice and serve as MPN initiating cells. Therefore, we further investigated how endogenous oncogenic Nras signaling regulates the self-renewal and differentiation of HSCs to promote leukemia development in different lineages of cells. Here we show that G12D/+ signaling results in moderate hyperproliferation and increased self-renewal of HSCs, promoting expansion of myeloid progenitors and consequently myeloid malignancies. In contrast, G12D/G12D leads to excessive hyperproliferation, decreased self-renewal, and depletion of HSCs, which promote expansion of myeloid and lymphoid progenitors and subsequently malignancies in both compartments. Because leukemia development in Nras G12D/+ and G12D/G12D models is tightly associated with ERK1/2 hyperactivation in haematopoietic stem/progenitor cells (HSPCs), we studied the MEK/ERK signaling in HSCs and their downstream multipotent progenitors (MPPs) using a “HSC phosphor-flow” method we developed. Our data demonstrate that ERK1/2 is hyperactiavated in G12D/+ and G12D/G12D HSCs in a dose-dependent manner, while AKT is not affected in G12D/+ and G12D/G12D HSCs. In contrast, both ERK1/2 and AKT are not changed in G12D/+ and G12D/G12D MPPs. As expected, inhibition of MEK/ERK signaling by AZD6244 (a MEK1 inhibitor) rescues the HSC phenotypes and attenuates myeloproliferative neoplasm phenotypes in G12D/+ and G12D/G12D mice. Mechanistic analysis identifies that a cohort of MAPK pathaway genes regulating cell cycle and signaling are significantly differentially expressed in G12D/+ HSCs compared to control or G12D/G12D HSCs. Unlike the prevailing theory based on Ras overexpression studies, depletion of G12D/G12D HSCs is not associated with overexpression of cell senescence genes. Rather, the Wnt and Notch pathways are significantly downregulated in G12D/G12D but not G12D/+ HSCs. Therefore, we propose that endogenous Nras G12D signaling differentially regulates HSCs self-renewal and differentiation through a dose-dependent hyperactivation of ERK1/2. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Dnmt3a Haploisufficiency Cooperates with Oncogenic Kras to Promote an Early-Onset T-Cell Leukemia

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2729-2729
Author(s):  
Yuan-I Chang ◽  
Guangyao Kong ◽  
Jing Zhang ◽  
Erik A. Ranheim
Keyword(s):  
T Cell ◽  
Dna Methyltransferase ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Myeloproliferative Neoplasm ◽  
Dominant Negative ◽  
Dependent Manner ◽  
Myeloid Malignancies ◽  
Dose Dependent

Abstract Recent whole genome/exome sequencing efforts in myeloid malignancies identified that mutations in DNA methyltransferase 3A (DNMT3A) are prevalent in acute myeloid leukemia (AML). In addition, DNMT3A mutations are also identified in various T cell malignancies. Of note, DNMT3A mutations are typically heterozygous and some WT DNMT3A functions thus remain in this state. However, the predominant DNMT3A R882 mutations, which locate in the catalytic domain, seem to inhibit the methyltransferase activity of the remaining WT DNMT3A due to its dominant-negative function (Yang L, Rau R, Goodell MA, Nat. Rev. Cancer 15: 152-165, 2015). COSMIC database analysis reveals different prevalence of DNMT3A R882 mutations in various hematopoietic malignancies. Approximately 60% of DNMT3A mutations in AML are R882 mutations, while the frequency of R882 mutations drops to ~40% in myelodysplastic syndrome (MDS) and myeloproliferative neoplasm (MPN). In contrast, the frequency of R882mutations is less than 25% in T-cell acute lymphoblastic leukemia (T-ALL). The significantly different frequencies of DNMT3A R882 mutations in AML versus T-ALL inspired us to investigate whether downregulation of DNMT3A regulates malignancies of different lineages in a dose-dependent manner. We previously showed that Dnmt3a-/- promotes MPN progression in KrasG12D/+ mice and ~1/3 compound mice develop AML-like disease (Chang et al. Leukemia 29: 1847-1856, 2015). Here, we generated KrasG12D/+; Dnmt3afl/+; Mx1-Cre mice to determine how Dnmt3a haploisufficiency affects KrasG12D/+-induced leukemogenesis. After pI-pC injections to induce Mx1-Cre expression, primary KrasG12D/+; Dnmt3a+/- mice died quickly as primary KrasG12D/+ mice; the survival rates of these two groups of animals were not significantly different. However, in a competitive transplant setting, recipients transplanted with KrasG12D/+; Dnmt3a+/- bone marrow cells displayed a significantly shortened survival than recipients with KrasG12D/+ cells. Moreover, all of the recipients with KrasG12D/+; Dnmt3a+/- cells developed a lethal T-ALL without significant MPN phenotypes, while ~20% of recipients with KrasG12D/+ cells developed MPN with or without T-ALL. This is in sharp contrast to the recipients with KrasG12D/+; Dnmt3a-/- cells, in which ~60% developed a lethal myeloid malignancy (MPN or AML). Our data suggest that in the context of oncogenic Kras, loss of Dnmt3a promotes myeloid malignancies, while Dnmt3a haploisufficiency induces T-ALL. This dose-dependent phenotype is highly consistent with the prevalence of DNMT3A R882 mutations in AML versus T-ALL in human. We are currently investigating the underlying mechanisms. Disclosures No relevant conflicts of interest to declare.

Endogenous Oncogenic Nras Signaling Promotes Proliferative Exhaustion of Hematopoietic Stem Cells Through a Dose-Dependent Hyperactivation of ERK,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3997-3997
Author(s):  
Jinyong Wang ◽  
Yangang Liu ◽  
Juan Du ◽  
Myung-Jeom Ryu ◽  
Erik A. Ranheim ◽  
...  
Keyword(s):  
Stem Cells ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Embryonic Stem ◽  
Erk Signaling ◽  
Significant Differential Expression ◽  
Self Renewal ◽  
Potent Inducer ◽  
Hematopoietic Stem ◽  
Dose Dependent

Abstract Abstract 3997 Both monoallelic and biallelic oncogenic NRAS mutations are identified in human leukemias, suggesting a dose-dependent role of oncogenic NRAS in leukemogenesis. We recently characterized conditional mouse models that express one or two copies of constitutively active Nras G12D in the hematopoietic compartment (Nras G12D/+ and Nras G12D/G12D). Nras G12D/G12D results in stronger downstream signaling than Nras G12D/+ and consequently distinct hematopoietic phenotypes. In particular, we found that somatic expression of Nras G12D/G12D but not Nras G12D/+ leads to an acute myeloproliferative neoplasm (MPN). The development of acute MPN is associated with cytokine-evoked hyperactivation of ERK but not Stat5 and Akt in hematopoietic stem/progenitor cells (HSPCs). Interestingly, genetically altered HSCs appear to be required for initiation and maintenance of chronic and acute MPD phenotypes mediated by Nras G12D/+ and Nras G12D/G12D, respectively. Furthermore, Nras G12D/G12D-mediated signaling promotes excessive HSC proliferation and leading to HSC exhaustion. Exhaustion of HSCs is tightly associated with diminished MPN phenotypes in non-engineered recipient mice into which Nras G12D/G12D HSCs are transferred by bone marrow transplantation. To investigate the molecular mechanisms underlying the exhaustion of Nras G12D/G12D HSCs, we performed a microarray analysis using highly purified control, Nras G12D/+, and Nras G12D/G12D HSCs. To our surprise, neither p16INK4a and p15INK4b, critical cell senescence genes, or other genes or pathways known to involve in HSC self-renewal were differentially expressed in Nras G12D/G12D HSCs. In contrast, gene ontology analysis revealed significant differential expression of genes in the MEK/ERK pathway in Nras G12D/G12D HSCs. This result is consistent with our phospho-flow study showing that Nras G12D/G12D selectively hyperactivates ERK in HSPCs. It has been documented that prolonged ERK signaling is a potent inducer of differentiation in cultured PC12 cells and inhibition of normal ERK signaling by a chemical inhibitor increases self-renewal in mouse embryonic stem cells. Thus, we are currently testing whether hyperactivation of ERK promotes depletion of Nras G12D/G12D HSCs through promoting HSC differentiation and whether blocking hyperactivation of ERK restores the normal HSC function and prevents MPN development. Disclosures: No relevant conflicts of interest to declare.

Distinct Roles for the NF-κB Pathway In Myeloid and Lymphoid Transformation and Leukemogenesis by BCR-ABL.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1225-1225
Author(s):  
Mo-Ying Hsieh ◽  
Richard A. Van Etten
Keyword(s):  
Stem Cells ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Myeloproliferative Neoplasm ◽  
Dominant Negative ◽  
Lymphoid Cells ◽  
Leukemic Cells ◽  
Mutant Form ◽  
B Lymphoid

Abstract Abstract 1225 The BCR-ABL tyrosine kinase, product of the t(9;22) Ph chromosome, activates multiple signaling pathways in leukemic cells from patients with chronic myeloid leukemia (CML) and Ph+ B-cell acute lymphoblastic leukemia (B-ALL). Previous studies have shown that NF-κB is activated in BCR-ABL-expressing cell lines and contributes to transformation of primary B-lymphoid cells by BCR-ABL (Reuther et al., Genes Dev. 1998;12:968), but the mechanism of activation has not been defined (Kirchner et al., Exp. Hematol. 2003;31:504), and importance of NF-kB to myeloid and lymphoid leukemogenesis by BCR-ABL is unknown. To interrogate the role of NF-κB in BCR-ABL-mediated transformation, we utilized a super-repressor mutant form of IκBα (IκBαSR), which has been used to block NF-κB nuclear localization and transactivation by constitutively sequestering NF-κB in the cytoplasm. Using retrovirus co-expressing BCR-ABL and IκBαSR, we found that IκBαSR blocked nuclear p65/RelA expression and inhibited the IL-3 independent growth of Ba/F3 cells and primary B-lymphoid cells transformed by BCR-ABL. The effect of NF-κB inhibition was primarily on proliferation rather than on cell survival, as there was no increase in apoptosis in cells expressing IκBαSR. When primary bone marrow cells were transduced and transplanted under conditions favoring induction of B-ALL or CML-like myeloproliferative neoplasm in recipient mice, co-expression of IκBαSR significantly attenuated disease development and prolonged survival of diseased mice. Molecular analysis of these leukemias demonstrated that NF-κB inhibition decreased the frequency of leukemia-initiating (“stem”) cells in the CML model, but not in the B-ALL model, and was associated with decreased expression of c-Myc, an NF-κB target. To clarify the mechanism of activation of NF-κB in BCR-ABL-expressing cells, we targeted two upstream kinases that negatively regulate IκBα, IKKα/IKK1 or IKKβ/IKK2. To accomplish this, we engineered retroviruses co-expressing BCR-ABL and kinase-inactive, dominant-negative mutants of IKK1 (IKK1KM) or IKK2 (IKK2KM). Co-expression of either IKK mutant inhibited both B-lymphoid transformation and leukemogenesis by BCR-ABL, as well as induction of CML-like MPN, with IKK1 inhibition more effective than IKK2. Together, these results demonstrate that NF-κB is activated in part through the canonical IKK pathway in BCR-ABL-expressing leukemia cells, and that NF-κB signaling plays distinct roles in the pathogenesis of myeloid and lymphoid leukemias induced by BCR-ABL. In CML, NF-κB may play a role for in generation and/or maintenance of leukemic stem cells. These results validate IKKs as targets for therapy in Ph+ leukemias, and motivate the evaluation of small molecule IKK inhibitors in these diseases. Disclosures: No relevant conflicts of interest to declare.

Oncogenic Nras Increases Hematopoietic Stem Cell Proliferation and Self-Renewal Through a Bimodal Effect

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 119-119
Author(s):  
Qing Li ◽  
Natacha Bohin ◽  
Tiffany Wen ◽  
Kevin M. Shannon ◽  
Sean J. Morrison
Keyword(s):  
Stem Cells ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasm ◽  
Mek Inhibitor ◽  
Ras Signaling ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Activating Mutations ◽  
Cycle Regulation

Abstract Abstract 119 Accumulating evidence suggests that most leukemias are initiated by rare leukemic stem cells (LSC) that are transformed from the normal hematopoietic stem cells and progenitors (HSC/P) by genetic lesions that lead to activation of oncogenes and inactivation of tumor suppressor genes. However, the signaling mechanisms by which these genes transform HSC/P into LSC are poorly understood. Activating mutations of NRAS and KRAS are highly prevalent in acute myeloid leukemia (AML), some myeloproliferative neoplasm (MPN) and myelodysplastic syndromes (MDS). In addition other leukemia associated genetic lesions, such as the BCR-ABL fusion, PTPN11 mutations, FLT3 internal tandem duplications, and NF1 inactivation all deregulate Ras signaling. We previously developed a mouse strain that conditionally expresses an oncogenic NrasG12D allele from the endogenous locus. This consistently resulted in an indolent MPD with delayed onset and prolonged survival in Mx1-cre, NrasG12D/+ mice (referred to as NrasG12D). Oncogenic NrasG12D, however, cooperated with the MOL4070LTR retrovirus to induce AMLs that share molecular and morphologic features with human M4/M5 AML. Here we report that NrasG12D directly affects HSC/P functions. While normal HSCs must remain quiescent to maintain the long term self-renewal capacity and mutations that drive HSC into cycle often lead to HSC depletion, NrasG12D increased HSC proliferation but at the same time increased the self-renewal and competitiveness of HSCs. Serial transplantations revealed that NrasG12D HSCs were able to give higher level of reconstitution than wild-type (WT) HSCs and gave rise to long term multi-lineage reconstitution in lethally irradiated mice after up to four rounds of transplantation while WT HSCs failed to reconstitute beyond two rounds. These effects were not associated with the development of leukemia suggesting oncogenic Nras dys-regulates HSC at a pre-leukemic stage and therefore plays an important role in leukemia initiation. Using histone-2B-GFP (H2B-GFP) label-retaining assays, we further detected a “bimodal” effect of NrasG12D on HSCs: NrasG12D induced a subpopulation of rapid “cycling” HSCs that lost GFP labeling and reconstitution activity faster than WT HSC but another HSC subpopulation that remained more “quiescent” than WT HSCs and retained higher reconstitution when transplanted to irradiated mice. The canonical Ras effector, ERK, was not activated in NrasG12D HSC/Ps and inhibition of ERK with a MEK inhibitor, PD325901, did not have any effect on the Nras induced increase of HSC proliferation. Stat5, on the other hand, was significantly activated in NrasG12D HSC/Ps and heterozygous knockout of Stat5ab abolished the increased proliferation in NrasG12D HSCs, suggesting that Stat5 signaling mediates at least part of the Nras induced increase in HSC proliferation. Nras is thus the first signaling pathway that simultaneously increases HSC proliferation, self-renewal and competitiveness without inducing frank leukemogenesis. This is likely through a “bimodal” effect of Nras signaling on HSC cell cycle regulation. Our studies also identified Stat5 as a novel therapeutic target to inhibit early events in Ras mediated leukemic transformation. Disclosures: No relevant conflicts of interest to declare.

Inactivation of p38 MAPK Extends Self-Renewal Capacity of Haematopoietic Stem Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 265-265
Author(s):  
Keisuke Ito ◽  
Atsushi Hirao ◽  
Fumio Arai ◽  
Sahoko Matsuoka ◽  
Keiyo Takubo ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
P38 Mapk ◽  
Cell Population ◽  
Critical Role ◽  
Dependent Manner ◽  
Self Renewal ◽  
Haematopoietic Stem Cells ◽  
P38 Inhibitor

Abstract Haematopoietic stem cells (HSCs) undergo self-renewing cell divisions and maintain blood production for their lifetime. Appropriate control of HSC self-renewal is critical for maintenance of haematopoietic homeostasis. Here we show that activation of p38 MAPK limits lifespan of HSCs in response to increasing levels of reactive oxygen species (ROS) in vivo. Although normal quiescent HSCs maintain a low level of oxidative stress, an increase in ROS was observed in HSCs after transplantation as well as in aged mice. In vitro treatment with BSO (Buthionine sulfoximine), which depletes intra-cellular glutathion, increased ROS (H2O2) level in immature hematopoietic cell population, c-kit+Sca1+Lin- (KSL) cells, in a dose-dependent manner. Low dose concentration of BSO suppressed reconstitution capacity of HSCs, whereas higher concentration did not affect progenitors. These data indicate that HSCs are much more sensitive to increased ROS than progenitors and are consistent with our previous results from Atm−/− mice in which ROS level is elevated in vivo. Here we focused on MAPKs for the stem cell dysfunction since it has been shown that several MAPKs are activated in response to ROS. We evaluated effects of MAPK inhibitors for p38, JNK or ERK in incubation of KSL cell with BSO. p38 inhibitor (SB203580), neither JNK nor ERK inhibitor, restored reconstitution capacity of HSCs after transplantation, suggesting that activation of p38 may contributes to defect of stem cell function in vivo. To address the question, we evaluated p38 activation in Atm−/− BM cells by immunohistochemistry. Surprisingly, p38 protein was phosphorylated only in KSL cells, but not other more differentiated cell populations, despite that the ROS levels were comparable among the cell population of mice. In response to activation of p38, p16INK4a was up-regulated only in KSL cells. The data indicates a possibility that stem cell-specific p38 activation negatively regulates self-renewal of HSCs. We then investigated a role of p38 activation on self-renewal of HSCs in vivo. When p38 inhibitor was intraperitoneally administered both before and after BMT, the level of repopulation achieved was comparable to that of the wild-type. Furthermore, Atm−/− mice that received long-term p38 inhibitor treatment did not show either anemia, a decrease in progenitor colony-forming capacity, or reduced frequencies of stem cell subsets. These data demonstrate that the activation of p38 present in HSCs promotes the exhaustion of stem cell pool in response to elevation of ROS. It has been proposed that aging is driven in part by a gradual depletion of stem cell functional capacity. There are evidences that inappropriate production of oxidants is connected to aging and life span. We propose a possibility that p38 activation in response to ROS plays a critical role for limit of stem cell capacity.

CITED2 Cooperates with Low PU.1 and DNMT3A to Maintain Self-Renewal in Hematopoietic Stem Cells

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 309-309
Author(s):  
Hein Schepers ◽  
Patrick Korthuis ◽  
Marjan Geugien ◽  
Jennifer Jaques ◽  
Tihomira I. Todorova ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Stem Cells ◽  
Conflicts Of Interest ◽  
Ectopic Expression ◽  
Gene Expression Pattern ◽  
Dependent Manner ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Specific Subset

Abstract CITED2 has a conserved role in the maintenance of normal hematopoiesis. We have recently shown that ~70% of acute myeloid leukemia (AML) patients display enhanced CITED2 expression levels. Interfering with CITED2 expression is detrimental for leukemia maintenance in vitro and in vivo, demonstrating that CITED2 is critically important for the survival of leukemic stem cells (LSCs). Ectopic expression of CITED2 in normal CD34+ stem and progenitor cells (HSPCs) led to significantly better human engraftment in transplanted NSG mice, consistent with the maintenance of very primitive lin- CD34+ CD38- CD90+ CD45RA- HSCs within the bone marrow 28 weeks after transplantation. Although the CITED2-engrafted mice displayed enlarged spleens, blood development appeared normal, as measured through myeloid, B and T cell staining. This indicates that CITED2 as a single hit is not sufficient to transform human CD34+ cells. CITED2 expression frequently coincides with low expression of the myeloid transcription factor PU.1, suggesting that combined effects, rather than single events are important during AML development. To investigate this, we combined lentiviral downregulation of PU.1 with overexpression of CITED2 (PU.1Low-CITED2High) and studied hematopoietic development. CITED2 increased the percentage of immature CD34+ CD38- cells 5-fold, which was not further increased by the additional downregulation of PU.1. However, functional analysis through limiting dilution LTC-iC assays indicated that combining PU.1 down-, with CITED2 upregulation led to a synergistic 8.5-fold increase in LTC-iC frequency, whereas only changing PU.1 or CITED2 induced a respective 1.4 to 3-fold change in HSC frequency. To more stringently assess self-renewal, we cultured transduced cells for 4 weeks on MS5 cells under myeloid differentiating conditions (G-CSF, IL3 and TPO) and subsequently performed CFC assays. Whereas after 4 weeks all groups displayed similar colony numbers, secondary and tertiary replatings demonstrated that self-renewal could only be maintained for more than 10 weeks when CITED2 upregulation was combined with PU.1 downregulation. This replating capacity of PU.1Low-CITED2High cells was limited to CD34+ CD38- HSCs, as replating of CD34+ CD38+ progenitor-derived colonies did not yield new CFCs. In order to investigate the underlying mechanisms, we performed transcriptome analysis on human HSCPs after knockdown of PU.1, overexpression of CITED2 or the combination of both. PU.1Low-CITED2High cells displayed a gene expression pattern different from the PU.1Low or CITED2High only cells, suggesting that the two events have synergistic effects. Some genes, like HLX and SF3B1 have been shown to cause or are mutated in AML, demonstrating that the synergistic changes are related to AML. When comparing the differentially regulated genes in the PU.1Low -CITED2High cells to the gene expression in the Hemaexplorer database, a similar pattern was observed, when compared between AML and normal cells. In order to investigate the effects of the PU.1low CITED2high combination on AML development, we resorted to a PU.1-dependent mouse model of AML development. CITED2 expression in BM cells from PU.1KD/KD mice (in which deletion of an Upstream Regulatory Element leads to an 80% downregulation of PU.1), led to a steady increase of GFP+ cells over time as compared to control cells and demonstrated a dramatic expansion of Gr-1+ Mac-1+ cells, a hallmark of AML in these mice. This suggests that CITED2 contributes to a faster progression towards AML upon lowering of PU.1. To identify if our model corresponds to AMLs with a specific subset of mutations, we clustered publically available AML data (TCGA), based on the gene expression changes in the PU.1Low -CITED2High cells. The majority of AMLs clustered together in 2 groups, in which FLT3, p53 and DNMT3A mutations were most prevalent. FLT3 mutations, through its activation of STAT5, are consistent with high CITED2 expression, whereas p53 mutations are consistent with our data indicating that CITED2 loss regulates HSCs in a p53-dependent manner. The presence of DNMT3A mutations suggests that DNA methylation changes collaborate with high CITED2 and low PU.1 during leukemogenesis. This is currently under investigation. In summary, our data imply that CITED2, low PU.1 and potentially changes in DNA methylation all contribute to maintenance of self-renewal and leukemogenesis. Disclosures No relevant conflicts of interest to declare.

Stem Cell Programs Are Retained In Human Leukemic Lymphoblasts With Distinct Immunophenotypes

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4995-4995
Author(s):  
Dengli Hong
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Conflicts Of Interest ◽  
Molecular Model ◽  
Normal Population ◽  
Lymphoblastic Leukemia ◽  
Bioinformatic Analysis ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Renewal Program

Abstract Leukemic lymphoblasts within different immunophenotypic populations possess stem cell Property. It remains largely unknown however whether self-renewal Program is retained from stem cells or endowed to Progenitors by leukemogenic molecules. We have addressed this issue in the context of TEL-AML1-associated acute lymphoblastic leukemia (ALL) by profiling a refined Program edited from genes essential for self-renewal of hematopoietic stem cells and B-cell development. Bioinformatic analysis shows that ALL populations are loosely clustered and all most close to the normal population that contains early lymphoid Progenitors, indicating that immunophenotypes do not reflect maturation stages in ALL and that self-renewal Program might be retained from stem cells. Results of assessing “first hit” function of TEL-AML1 in different populations of normal cells demonstrate the molecular model. Therefore, our studies reveal a leukemogenic scenario of human ALL that programs of stem cells are sustained in distinct fractions by leukemogenic mutations. Disclosures: No relevant conflicts of interest to declare.

Tumor Suppressor Role of HIF-1alpha in Leukemia-Initiating Cells in Flt3-ITD-Induced Myeloproliferative Neoplasm

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3578-3578
Author(s):  
Talia Velasco ◽  
Jörg Cammenga
Keyword(s):  
Stem Cells ◽  
Tumor Suppressor ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasm ◽  
Molecular Response ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Hypoxia-induced signalling is a major regulator in normal and malignant hematopoiesis. The transcription factor HIF-1alpha plays a crucial role in the quiescence and self-renewal of hematopoietic stem cells as well as leukemia-initiating cells (LICs) of acute myeloid leukemia and chronic myeloid leukemia. Better understanding of the requirement of the molecular response to hypoxia in LICs could lead to new therapies targeting this pathway. We have therefore investigated the effect of HIF-1alpha loss on the phenotype and biology of FLT3-ITD induced myeloproliferative neoplasm (MPN). Using a combined transgenic mouse model (Mx1-Cre; Hif-1alphafl/fl; Flt3ITD/+) we showed that deletion of HIF-1alpha leads to a more severe MPN phenotype reflected by higher numbers of white blood cells and myeloid cells in peripheral blood, as well as a more severe splenomegaly. Loss of long-term hematopoietic stem cells (LT-HSCs: Lin- Sca1+ cKit+ CD48- CD150+) and increased number of lineage-restricted progenitors (Lin- Sca1+ cKit+ CD48+ CD150-) were the most pronounced effects on a cellular level upon the loss of HIF-1alpha. The proliferative effect of the HIF-1alpha loss was cell intrinsic and not at the expense of the ability of the LICs to self-renew because the disease was transplantable into secondary recipients recapitulating the same phenotype. Mice transplanted with FLT3-ITD induced MPN lacking HIF-1alpha succumbed to their disease (average survival of 35 weeks after transplant), while animals transplanted with MPN with wild-type HIF-1alpha suffered from MPN but did not die in the observation period of 60 weeks. These findings are in contrary to what has been previously described for the role of HIF-1alpha in leukemia initiating cells and lead us to propose that HIF-1alpha could act as a tumor suppressor gene, inhibiting proliferation in myeloid malignancies. Our results provide evidence that targeting HIF-1alpha can lead to disease progression of MPN while not affecting self-renewal of LICs. Disclosures No relevant conflicts of interest to declare.

scholarly journals Wnt5a Signaling in Normal and Cancer Stem Cells

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Yan Zhou ◽  
Thomas J. Kipps ◽  
Suping Zhang
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cancer Progression ◽  
Molecular Mechanisms ◽  
Migration And Invasion ◽  
Target Cells ◽  
Dependent Manner ◽  
Self Renewal ◽  
Surface Receptors ◽  
Canonical Wnt

Wnt5a is involved in activating several noncanonical Wnt signaling pathways, which can inhibit or activate canonical Wnt/β-catenin signaling pathway in a receptor context-dependent manner. Wnt5a signaling is critical for regulating normal developmental processes, including stem cell self-renewal, proliferation, differentiation, migration, adhesion, and polarity. Moreover, the aberrant activation or inhibition of Wnt5a signaling is emerging as an important event in cancer progression, exerting both oncogenic and tumor suppressive effects. Recent studies show the involvement of Wnt5a signaling in regulating normal and cancer stem cell self-renewal, cancer cell proliferation, migration, and invasion. In this article, we review recent findings regarding the molecular mechanisms and roles of Wnt5a signaling in stem cells in embryogenesis and in the normal or neoplastic breast or ovary, highlighting that Wnt5a may have different effects on target cells depending on the surface receptors expressed by the target cell.

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