Inherited and Acquired RUNX1 Mutations in Hematologic Disorders

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. SCI-5-SCI-5
Author(s):  
Nancy A. Speck ◽  
Xiongwei Cai ◽  
Jingping Ge ◽  
Philip J. Mason
Keyword(s):  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Conflicts Of Interest ◽  
P53 Protein ◽  
Lymphoblastic Leukemia ◽  
Genotoxic Stress ◽  
Myelogenous Leukemia ◽  
Phenotypic Properties ◽  
Hematopoietic Stem ◽  
Protein Levels

Abstract RUNX1, a DNA binding subunit of core binding factors, is frequently mutated or rearranged in hematopoietic malignancies, including acute myelogenous leukemia (AML), chronic myelomonocytic leukemia, acute lymphoblastic leukemia, and myelodysplastic syndrome (MDS). Mutations in RUNX1 can be early events in leukemia, and generate a long-lived pre-leukemic stem cell (pre-LSC). Additionally, it has been reported that loss of function RUNX1 mutations are particularly frequent in radiation-associated MDS and AML, suggesting that pre-existing RUNX1 mutations in a pre-LSC may predispose patients to MDS/AML following DNA damage. Discussion will focus on the phenotypic properties of Runx1-deficient pre-LSCs, and the mechanisms by which Runx1 deficiency contributes to these phenotypes. Pan-hematopoietic Runx1 loss in mice causes a G1 to S-cell cycle delay and decreases apoptosis of pre-LSCs. Runx1-deficient pre-LSCs are radiation- and chemotherapy-resistant, and this correlates with decreased p53 protein levels and an attenuated p53 pathway response. Both p53 protein levels and apoptosis are increased following treatment with Nutlin-3. Runx1-deficient pre-LSCs are smaller, consume less glucose, and produce less ATP than normal hematopoietic stem cells (HSCs). Runx1-deficient stem and progenitor cells have lower overall ribosomal content and skewing in the relative amounts of rRNA and mRNA encoding ribosomal proteins. Analysis of AKT pathway components suggests that the decreased ribosome biogenesis is unlikely to be primarily caused by lower AKT signaling. We hypothesize that one or more of the above-mentioned properties (low p53 levels, decreased metabolism) render Runx1-deficient pre-LSCs less sensitive to genotoxic stress than normal HSCs, allowing a Runx1-deficient pre-LSC population to both perdure and expand in the bone marrow. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Stress Hematopoiesis Reveals Abnormal Control of Self-Renewal, Lineage-Bias and Myeloid Differentiation in Mll Partial Tandem Duplication (Mll-PTD) Hematopoietic Stem/Progenitor Cells

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3501-3501
Author(s):  
Yue Zhang ◽  
Xiaomei Yan ◽  
Goro Sashida ◽  
Xinghui Zhao ◽  
Yalan Rao ◽  
...  
Keyword(s):  
Mouse Model ◽  
Tandem Duplication ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Myelogenous Leukemia ◽  
Myeloid Differentiation ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Mll Gene ◽  
Partial Tandem Duplication

Abstract Abstract 3501 Rearrangements of the Mixed-Lineage Leukemia (MLL) gene occur in a variety of aggressive human leukemias. The most common ones are balanced translocations in which the genomic sequences encoding the N-terminal portion of MLL are fused to sequences encoding the C-terminus of another translocation partner in acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL). Another mechanism for disrupting the MLL gene in myelodysplastic syndrome (MDS) and AML, but rarely seen in ALL, is partial tandem duplication (MLL-PTD). The MLL–PTD was first identified in de novo AML with a normal karyotype or trisomy 11. Cloning of this region revealed partial duplications within the 5′ region of the MLL gene. These duplications consist of an in-frame repetition of MLL exons in a 5′–3′ direction and produce an elongated protein. The incidence of MLL–PTD was 8% in unselected adult and childhood AML and 5% in MDS. However, the mechanism by which MLL-PTD contributes to MDS and AML development and maintenance is currently unknown. Mll-PTD knock-in mouse model, its expression is regulated by endogenous promoter, has been generated to study the function of Mll-PTD in vitro and in vivo and to identify its downstream targets. This mouse model provides a powerful genetic tool to identify disruptions in normal cellular regulation as a result of this mutation, as well as a model to characterize the contribution of the Mll-PTD in leukemogenesis. Herein, we investigated hematopoietic stem/progenitor cell (HSPC) phenotypes of Mll-PTD knock-in mice. Although HSPCs (Lin−Sca1+Kit+ (LSK)/SLAM+ and LSK) in MllPTD/WT mice are reduced in absolute number in steady state due to increased apoptosis, they have a proliferative advantage in colony replating assays, CFU-spleen assays, and competitive transplantation assays over wild-type HSPCs. The MllPTD/WT–derived phenotypic short-term (ST)-HSCs/multipotent progenitors (MPPs) and granulocyte/macrophage progenitors (GMPs) have self-renewal capability, rescuing hematopoiesis by giving rise to long-term repopulating cells in recipient mice with an unexpected myeloid differentiation blockade and lymphoid-lineage bias. However, MllPTD/WT HSPCs never develop leukemia in primary or recipient mice, suggesting that additional genetic and/or epigenetic defects are necessary for full leukemogenic transformation. In conclusion, the MllPTD/WT mouse model provides unique genetic and biochemical tool to identify new targets and pathways responsible for the altered differentiation/repopulating properties, self-renewal activity, lineage bias and myeloid differentiation blockade relevant to MLL-PTD MDS and AML. This model should also help us to understand the underlying mechanism(s) for each of the phenotypes we found in this study and facilitate improved therapies and patient outcomes in the future. Disclosures: No relevant conflicts of interest to declare.

Serious Late Complications After Hematopoietic Stem Cell Transplantation (HSCT) Following Myeloablative Conditioining (MAC) In Infants.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4501-4501
Author(s):  
Masahiro Yasui ◽  
Kayo Yamada ◽  
Osamu Kondo ◽  
Maho Sato ◽  
Akihisa Sawada ◽  
...  
Keyword(s):  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Hormone Secretion ◽  
Body Height ◽  
Growth Hormone Secretion ◽  
Late Complications ◽  
Myelogenous Leukemia ◽  
Endocrine Disorders ◽  
Hematopoietic Stem ◽  
Secondary Cancers

Abstract Abstract 4501 Background: Recently, HSCT has been widely used as a curative therapy for refractory hematological/malignant diseases. However, late complications after HSCT such as endocrine disorders, infertility, short stature and secondary cancers have been recognized as serious problems in children. Late complications are assumed to be much more serious in younger children, especially in infants. Therefore, we retrospectively evaluated late complications among patients who underwent HSCT before one-year-old age in our institute to clarify this big issue. Methods and results: We performed HSCT in 530 children from 1993 to 2009. Among these 530 patients, 33 were infants (younger than 1- year - old) at HSCT. 23 infants with malignant disorders consisted of neuroblastoma 10, hepatoblastoma 2, rhabdomyosarcoma 1, retinoblastoma 1, acute lymphoblastic leukemia 5, myelodysplastic syndrome 2, acute myelogenous leukemia 2, and 10 infants with non-malignant disorders consisted of immunodeficiency 5, familial hemophagocytic lymphohistiocytosis/hemophagocytic syndrome 2, congenital metabolic disorder 1, severe aplastic anemia 1, pure red cell aplasia 1 were included. 9 infants underwent autologous HSCT and 24 underwent allogeneic HSCT. 22 infants received MAC and 11 received reduced-intensity conditioning (RIC). 26 out of 33 patients have been alive (MAC, 18/22 = 81.8 %; RIC, 8/11 = 72.7 %). Body height (BH) of 5 patients in RIC group who have been surviving longer than 5 years after HSCT is equal or taller than -2 standard deviation (SD) of BH. However, BH of 6 out of 13 evaluable patients in MAC group remains shorter than -2 SD (the shortest, -5.3 SD) of BH. All survivors in MAC group are suffering from one or more late complications such as growth hormone secretion insufficiency, premature puberty, hypothyroidism, gonadal failure and secondary cancers, therefore, they needs treatment and support for these late complications. Conclusions: The survival rate is similar (81.8 % versus 72.7 %) between MAC and RIC in infants, however, infants who underwent MAC-HSCT are suffering from late complications much more frequently and need treatment and support. These results suggest that less toxic conditioning should be adopted for infants who undergo HSCT to avoid serious late complications. Disclosures: No relevant conflicts of interest to declare.

High Musashi-2 Expression Is an Unfavorable Prognostic Factor in Adult B-Cell Acute Lymphoblastic Leukemia.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2508-2508
Author(s):  
Qitian Mu ◽  
Yungui Wang ◽  
Bing Chen ◽  
Wenbin Qian ◽  
Haitao Meng ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Prognostic Significance ◽  
Myelogenous Leukemia ◽  
High Expression ◽  
Expression Level ◽  
Hematopoietic Stem ◽  
Expression Levels ◽  
Hes1 Expression

Abstract Abstract 2508 Background: Musashi-2 (MSI2) can inhibit translation of the mRNA encoding NUMB, the NOTCH signaling inhibitor, and play a vital role in the maintenance of hematopoietic stem cells. Musashi-1 (MSI1), another isoform of Musashi family, positively regulates NOTCH1 expression. Recent studies have demonstrated that MSI2 expression was up-regulated during chronic myelogenous leukemia (CML) progression and its high expression was associated with poor outcome of CML and acute myeloid leukemia (AML). However, the prognostic significance of MSI2 expression and the relation between MSI2 and NOTCH1 expressions in acute lymphoblastic leukemia (ALL) remain unknown. Methods: In this study, real-time PCR was used to measured expression levels of MSI2 and NOTCH1 signaling related genes in 116 B-ALL and 24 T-ALL patients, in whom more than 70% leukemic cells were morphologically detected in bone morrow (BM) at diagnosis. Clinical and Molecular data in relation with MSI2 expression level were analyzed. Results: In our B-ALL cohort, although MSI2 expression was not associated with gender, age, white blood cell (WBC), t(9;22)/BCR-ABL and IK6 variant of IKZF1, patients with high MSI2 expression had inferior overall survival (OS) (P=0.007) and event free survival (EFS) (P=0.002) than patients with low MSI2 expression. Multivariate analysis showed that high MSI2 expression was an independently prognosic factor in OS (P=0.001, HR=2.641, 95%CI, 1.494–4.668), EFS (P<0.001, HR=2.562, 95%CI, 1.513–4.218) and RFS (P=0.043, HR=2.057, 95%CI, 1.023–4.137). Moreover, MSI2 expression level had a positive correlation with that of NOTCH1 (P<0.001), but not c-MYC (P=0.432) or HES1 (P=0.509). Similarly, NOTCH1 expression level in patients with high MSI2 expression (0.98, range 0.02 to 13.58) was significantly higher than that in patients with low MSI2 expression (0.42, range 0.01 to 3.55, P=0.001), but c-MYC and HES1 expression levels between patients with high MSI2 expression and low MSI2 expression showed no significant differences (both P>0.05). Conclusion: Our data suggests MSI2 high expression can indicate poor prognosis in adult B-ALL accompanying with elevated NOTCH1 expression but not activating NOTCH1 downstream pathway. Disclosures: No relevant conflicts of interest to declare.

41BBL-Based Activation and Expansion of Autologous Natural Killer Cells Results in Enhanced Activity Against Leukemia Including ALL

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2293-2293
Author(s):  
Ekta Kapadia ◽  
Elad Jacoby ◽  
Mark Kohler ◽  
Waleed Haso ◽  
Christopher Daniel Chien ◽  
...  
Keyword(s):  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
Conflicts Of Interest ◽  
Ex Vivo ◽  
Lymphoblastic Leukemia ◽  
Myelogenous Leukemia ◽  
Hematopoietic Stem ◽  
Enhanced Activity

Abstract Childhood leukemia is the most common pediatric malignancy. There are now excellent cure rates for these patients, however outcomes remain poor for those with refractory disease and for those who relapse after standard salvage therapies, with a disease recurrence of approximately 50%. Therefore, development of novel cellular therapies is essential to treat these refractory patients. Natural Killer (NK) cells generated from an allograft contribute to improved disease free survival after Hematopoietic Stem Cell Transplantation for leukemia when there is a KIR mismatch. This effect appears to be particularly potent in the setting of Acute Myelogenous Leukemia (AML) with less benefit demonstrated in Acute Lymphoblastic Leukemia (ALL). Preclinical studies have also suggested that activation and expansion of resting NK cells can enhance NK cell cytotoxicity and eliminate the need for KIR mismatch due to up-regulation of activating receptors. We are currently testing this approach in the clinic following a fully matched allogeneic transplant platform for leukemia. Our aim is to explore whether 41BB ligand (41BBL) and recombinant IL-15 (rIL-15) mediated ex vivo expansion of autologous NK cells results in enhanced activity against AML and ALL. The activation/expansion process may allow for the use of autologous NK cell infusions, thus eliminating the need for allogeneic NK cell donors. To test this hypothesis, we ex vivo expanded and activated NK cells derived from C57BL/6J (B6) mice using artificial Antigen Presenting Cells (aAPCs) containing 41BBL and rIL-15 for 7-14 days. NK cells were co-cultured with murine AML cells (C1498) and murine ALL cells (E2A-PBX) – both on B6 background. Controls included YAC cells (murine T-cell lymphoma cell line sensitive to NK cell killing) as well as Phorbol Myristate Acetate (PMA)/ionomycin. All cells were co-cultured for 5 hours prior to functional assessment of NK cells via CD107a degranulation. NK cells cultured with 41BBL aAPCs and rIL-15 had a 30-fold expansion in numbers (Figure 1) and an increase in purity to approximately 95-98% (NK1.1+, CD3–) by Day 7. In the absence of cytokine or aAPCs, cultured NK cells underwent rapid apoptosis. Functionally, although resting NK cells (harvested prior to assessment) expressed CD107a when cultured with YAC cells and PMA, only minimal degranulation was observed in the presence of autologous AML cells or ALL cells. In contrast, activated and expanded autologous NK cells displayed enhanced activity against ALL, AML, as well as YAC cells, while only minimal levels of CD107a were seen in the absence of targets (Figure 2). In vivo experiments with a single injection of activated and expanded NK cells did not result in prolonged survival of mice bearing either AML or ALL. Assessment of adoptively transferred NK cells demonstrated very transient persistence (<2 days) with no in vivo expansion, suggesting that repeated injections may be necessary for leukemia eradication. Future murine experiments will investigate the effect repeated injections of activated/expanded NK cells and/or the administration of rIL-15 will have on survival and leukemia eradication. In addition, the ability to activate and expand NK cells in culture provides an opportunity for lentiviral-based transduction with chimeric antigen receptor (CAR) vectors. We are currently testing this with a murine CD19 CAR. These experiments suggest that autologous activated and expanded NK cells may serve as a viable cellular therapy for pediatric patients with refractory/relapsed leukemia. As demonstrated in these in vitro experiments, autologous activated/expanded NK cells still show increased targeting of mouse AML and ALL cell lines despite the lack of KIR mismatch. Thus, they may serve as a potential platform for leukemia therapy, including ALL, which appear to be poor targets for resting NK cells. In addition, these cells demonstrate transient persistence in vivo, a potential advantage in the context of redirected cytotoxicity using CAR constructs that target antigens with broader expression in the hematopoietic compartment. Figure 1: <![if !vml]><![endif]> Figure 1:. <![if !vml]><![endif]> Figure 2: Figure 2:. Disclosures No relevant conflicts of interest to declare.

scholarly journals Hematopoietic Phf6 Deletion in Mice Causes HSC Depletion and Expansion of Myeloid Progenitors

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 3829-3829
Author(s):  
Roman Verner ◽  
Gabrielle Ochoco ◽  
Patrick Somers ◽  
Cristian Taborda ◽  
Vikram R Paralkar
Keyword(s):  
Bone Marrow ◽  
Peripheral Blood ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Conflicts Of Interest ◽  
Specific Binding ◽  
Lymphoblastic Leukemia ◽  
Cell Surface Receptor ◽  
The Common

Abstract PHF6 is an X-chromosome gene showing recurrent loss-of-function mutations in acute and chronic myeloid leukemias and T-lymphoblastic leukemia, indicating that it acts as a tumor suppressor in both myeloid and lymphoid hematopoietic lineages. PHF6 protein is localized to the nucleolus, the site of ribosome biogenesis, where it is reported to regulate rDNA transcription. It is also localized to the nucleoplasm, where it binds chromatin and may regulate gene transcription. However, these mechanisms are incompletely established, no animal model of PHF6 loss has been reported, and there is limited insight into the precise role of PHF6 in hematopoiesis, both mechanistically and as a leukemia suppressor. To study the in vivo role of Phf6, we generated mice with hematopoietic knockout of Phf6 using the Vav-Cre recombinase system, achieving a >95% deletion efficiency. In comparison with Vav-Cre mice (WT), mice with Vav-Cre;Phf6-flox genotype (Phf6 KO) showed, at 8-12 weeks of age, a 1.25-fold expansion of the LSK (Lin-Sca1+Kit+) compartment in the bone marrow (see figure), accompanied with a similar increase in the common myeloid progenitor CMP compartment (Lin-Kit+Sca1-CD34+FcRIII-). Within the LSK compartment, there was a 2-fold and 1.7-fold expansion of the myeloid-biased multipotent progenitor compartments MPP2 (LSK,Flk2-CD150+CD48+) and MPP3 (LSK,Flk2-CD150-CD48+) respectively. The lymphoid-biased MPP4 compartment was not changed, nor was the common lymphoid progenitor CLP compartment (not shown). Conversely, the number of stringently defined HSCs (LSK,Flk2-CD150+CD48-CD34-) was reduced by 40%. This suggests depletion of HSCs through loss of dormancy, accompanied by myeloid skewing. At 8-12 weeks of age, there was no change in overall bone marrow cellularity or spleen size/cellularity, though flowcytometric analysis of spleen showed identical reduction of HSC and expansion of MPP2 compartments in Phf6 KO. As of 40 weeks of age, Phf6 KO mice did not show any gross peripheral blood count abnormalities. We also used CRISPR/Cas9 to generate PHF6 knockout clones from the THP-1 human AML cell line. RNA-Seq and quantitative proteomics in knockout cells showed downregulation of mature myeloid genes and increased expression of hematopoietic progenitor gene sets, including increased expression of cell surface receptor KIT. KO cells showed increased proliferation when cultured with KIT ligand. Using IP-mass spectrometry in WT and KO clones, we identified ribosomal proteins RPL12 and RPLP0 as the most abundant and specific binding partners of PHF6. In summary, young Phf6 knockout mice show HSC depletion and expansion of myeloid-skewed progenitors without overt peripheral blood abnormalities. Further work is in progress to characterize HSC dormancy and competitiveness, progression of Phf6 KO phenotype with age, and mechanisms of gene regulation by Phf6 through binding of ribosomal proteins. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

CD34+/CD38− Acute Myelogenous Leukemia Cells Aberrantly Express Aurora Kinase A

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1886-1886
Author(s):  
Jing Yang ◽  
Takayuki Ikezoe ◽  
Mutsuo Furihata ◽  
Chie Nishioka ◽  
Akihito Yokoyama
Keyword(s):  
Acute Myelogenous Leukemia ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Specific Inhibitor ◽  
Aurora Kinase ◽  
Myelogenous Leukemia ◽  
Hematopoietic Stem ◽  
Aurora Kinase A ◽  
Acute Myelogenous ◽  
Kinase A

Abstract Abstract 1886 Aurora kinase A (AURKA) plays a pivotal role in the mitotic processes during cell division. We previously showed that AURKA was aberrantly expressed in hematological malignant cells including those from acute myelogenous leukemia (AML) and acute lymphoblastic leukemia, compared with CD34+ hematopoietic stem/progenitor cells isolated from healthy volunteers. This study found that freshly isolated CD34+/CD38− cells from individuals with AML (n=12) in which leukemia stem cells were supposed to be enriched expressed a greater amount of AURKA than their CD34+/CD38+ counterparts, as measured by real time RT-PCR. Blockade of AURKA by the specific inhibitor MLN8237 significantly inhibited proliferation and induced apoptosis of CD34+/CD38− AML cells, as assessed by the clonogenic assay and detection of the cleaved form of poly (ADP-ribose) polymerase by Western blot analysis, respectively. In addition, exposure of CD34+/CD38− AML cells to MLN8237 down-regulated levels of Bcl-2 family proteins and increased Bax/Bcl-2 expression ratio. Moreover, inhibition of AURKA by MLN8237 (30mg/kg for 14 consecutive days) impaired engraftment of CD34+/CD38− AML cells in severely immunocompromised mice (n=5, 49±32% in control vs 18±16% in MLN8237 treated mice, P<0.05), and prolonged their overall survival (P<0.05), compared with vehicle treated mice. Taken together, AURKA may be a promising molecular target to eliminate chemotherapy-resistant CD34+/CD38− AML cells. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Leukemia-Initiating Activity in T-ALL Requires Active Hif1a and Wnt Signaling

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 57-57
Author(s):  
Vincenzo Giambra ◽  
Catherine E Jenkins ◽  
Sonya H Lam ◽  
Catherine Hoofd ◽  
Miriam Belmonte ◽  
...  
Keyword(s):  
Stem Cells ◽  
Wnt Signaling ◽  
Cell Biology ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Negative Regulator ◽  
Myelogenous Leukemia ◽  
Leukemia Stem Cells ◽  
Hematopoietic Stem

Abstract Prior work has shown that NOTCH1 is a prominent oncogene in T-cell acute lymphoblastic leukemia (T-ALL) with activating NOTCH1 mutations occurring in over 50% of cases (Weng et al, Science 2004) and loss-of-function mutations in its negative regulator FBXW7 occurring in 8-15% of cases (O’Neil et al, J Exp Med 2007; Thompson et al, J Exp Med 2007). Subsequent work has shown that continued Notch signaling is required for maintenance of T-ALL leukemia stem cells (Armstrong et al, Blood 2009; Tatarek et al, Blood 2011; Giambra et al, Nat Med 2012). Several lines of evidence have substantiated genetic interactions between the Notch and Wnt signaling pathways in various contexts, and Wnt signaling has been shown to play important roles in hematopoietic stem cell biology and also in hematopoietic cancers such as acute myelogenous leukemia (AML) and chronic myelogenous leukemia (CML) (reviewed in Luis et al, Leukemia 2012). To address what role if any Wnt signaling may play in T-ALL, we generated primary murine leukemias by viral transduction of bone marrow progenitors with activated NOTCH1, then delivered a fluorescent Wnt reporter construct (7TGP; Fuerer & Nusse, PLoS ONE 2010) by lentiviral transduction, and retransplanted the leukemias to interrogate Wnt signaling activity in vivo. We report here that active Wnt signaling is restricted to minor subpopulations within bulk T-ALL tumors, and that these Wnt-active subsets are highly enriched for leukemia-initiating cell (LIC) activity. Moreover, using Ctnnb1loxP/loxP animals we show that inducible Cre-mediated deletion of β-catenin or enforced expression of a dominant-negative TCF construct severely compromises LIC activity. We also show that β-catenin levels are upregulated by hypoxia through Hif1a stabilization, and that deletion of Hif1a also severely compromises LIC activity. Interestingly, Wnt-active subsets are distributed diffusely throughout the marrow interstitial space suggesting that tumor infiltration induces formation of local hypoxic niches as opposed to taking up residence in pre-existing anatomic compartments with low oxygen tensions. Taken together, these results suggest a model in which hypoxic niches in vivo facilitate Hif1a-dependent accumulation of β-catenin which drives Wnt signaling and self-renewal of leukemia stem cells. Finally, we show using patient-derived xenografts that antagonism of Hif1a or Wnt signaling also compromises human LIC activity, suggesting that pharmacologic targeting of these pathways could have therapeutic application in patients with T-ALL. Disclosures No relevant conflicts of interest to declare.

BCR/ABL Can Promote CD19+ Cell Growth but Not Render Them Long-Term Stemness

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2709-2709
Author(s):  
Donghe Li ◽  
Xuemei Zhao ◽  
Bo Jiao ◽  
Ping Liu ◽  
Ruibao Ren
Keyword(s):  
Stem Cells ◽  
Cancer Stem Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Chronic Phase ◽  
Myelogenous Leukemia ◽  
Leukemia Stem Cells ◽  
T Cell Therapy ◽  
Hematopoietic Stem

Abstract Cancer stem cells are a subpopulation of malignant cells that have the capacity of both self-renewal and reconstitution of the cancer. Eradication of cancer stem cells is crucial for curing the malignant disease. Previous studies in hematopoietic malignancies showed that leukemia stem cells (LSCs) in chronic myelogenous leukemia (CML) chronic phase are originated from a hematopoietic stem cell (HSC), while LSCs in acute myeloid leukemia (AML) can either be derived from HSCs or be transformed from myeloid progenitors. But in acute B-lymphoblastic leukemia (B-ALL), the origin of leukemia stem cells is not clear. In this study, we tested whether BCR/ABL could transform B-lineage committed CD19+ cells to LSCs. We found that transducing BCR/ABL in CD19+ cells can promote their colony formation in vitro and induce B-ALL like disease in vivo. However, only BCR/ABL transduced whole bone marrow cells, but not CD19+ cells, can be transplanted multiple times in recipient mice, and the frequency of long-term LSCs from the latter ranges from 1/135 to 1/629. These studies suggest that LSCs in BCR/ABL+ B-ALL may originate from CD19- hematopoietic stem/progenitor cells and that CD19 chimeric antigen receptor (CAR) modified T cell therapy may not be effective in eradicating LSCs in BCR/ABL+ B-ALL. Disclosures No relevant conflicts of interest to declare.

scholarly journals Ripk3 Signaling Regulates Hematopoietic Stem Cell Number and Function during Stress

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3714-3714
Author(s):  
Lei Zhang ◽  
Huacheng Luo ◽  
Jing Li ◽  
Hong-Min Ni ◽  
Mark Sellin ◽  
...  
Keyword(s):  
Inflammatory Cytokines ◽  
Low Dose ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
High Dose ◽  
Low Doses ◽  
Hematopoietic Stem ◽  
Increased Risk ◽  
Leukemia Development ◽  
Serial Transplantation

Background: Among all tissues, bone marrow (BM) is the most sensitive tissue to ionizing radiation (IR)-induced acute tissue damage (ATD) and chronic long-term residual damage (LT-RD). BM failure and a significant reduction in blood cells (pancytopenia) often occurs within days after exposure to IR due to the massive death of proliferative hematopoietic progenitor cells (HPCs). However, due to their quiescent cell cycle status and reduced fidelity of DNA repair feature, many hematopoietic stem cells (HSCs) cannot fully eliminate such damage and enter senescence; this results in LT-RD. Abnormal dysplastic hematopoiesis is the most common LT-RD in most victims of IR, followed by an increased risk of leukemia/lymphoma development. Thus IR exposure is an established cause of BM failure and leukemia. A significant increase in the production of inflammatory cytokines is induced by IR which contributes to the pathogenesis of both ATD and LT-RD. Such inflammatory cytokines induce the activation of Ripk3-Mlkl-mediated necroptotic signaling in HSCs. However, the role of Ripk3-Mlkl signaling in IR-induced damage has not studied. Experimental procedures: The self-renewal capacity of HSCs among Ripk3-/-, Mlkl-/- and WT mice were examined and compared by serial transplantation assay. The phenotypes of ATD and LT-RD induced by different dosages of IR were compared among Ripk3-/-, Mlkl-/- and WT mice. The mechanism by which Ripk3 signaling prevents IR-induced leukemia development was studied. Results: Ripk3-Mlkl signaling is not required for hematopoiesis during homeostatic condition. However, during serial transplantation, inactivation of such signaling prevents stress-induced loss of HSCs. Interestingly, Ripk3 signaling also induces an Mlkl-independent ROS-p38-p16-mediated senescence in HSCs. Thus Ripk3-/- HSCs showed better competitive hematopoietic ability compared to Mlkl-/- and WT HSCs during serial transplantation. A sub-lethal dosage of IR (6Gy) induces Ripk3-dependent NF-κB activation and pro-survival gene expression in HSCs, which is necessary for the survival of damaged HSCs. After 6Gy IR, although DNA damage is repaired in most HSCs within 2 days, a proportion of HSCs in WT and Mlkl-/- mice fail to fully repair the damage and undergo p53-p21-dependent senescence. However such cells in Ripk3-/- mice die from apoptosis. Thus the remaining HSCs in Ripk3-/- mice should be functionally normal, while a proportion of the remaining HSCs in Mlkl-/- and WT mice remain damaged but senescent, all as demonstrated by competitive hematopoietic reconstitution assay. Multiple low-doses of IR (1.75Gy once week × 4) induce HSC exhaustion in WT mice but not in Ripk3-/- and Mlkl-/- mice. Interestingly, almost all Ripk3-/- mice develop acute lymphoblastic leukemia within 200 days after such low dose IR, while 45% of WT and 60% of Mlkl-/- mice develop thymomas within 360 days (see Figure). Mechanistically, such low-dose IR stimulates chronic inflammatory cytokine production. Such cytokines induce Ripk3-Mlkl-mediated necroptosis in response to HSC exhaustion observed in WT mice. These cytokines also induce Ripk3-ROS-p38-p16-mediated senescence in response to impaired HSC functioning observed in both WT and Mlkl-/- mice. In Ripk3-/- mice, due to the lack of both necroptotic and senescent signaling, mutant HSCs accumulate and leukemia development is accelerated. Conclusion: Ripk3 signaling plays distinct roles in HSCs in response to different doses of IR. High-dose IR induces Ripk3-dependent NF-κB/survival signaling, which is required for the survival of HSCs which fail to repair the damage. Thus temporal inhibition of Ripk3-NF-κB signaling might help to remove the damaged HSCs thus preventing the occurrence of LT-RD. However multiple low-doses of IR induces Ripk3 activation in HSCs which represses leukemia development by inducing both ROS-p38-p16-mediated senescence and Ripk3-Mlkl-mediated necroptosis. Induced activation of Mlkl-necroptosis might help to repress leukemia development by removing damaged HSCs. Disclosures No relevant conflicts of interest to declare.

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.

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