Thrombopoietin responsiveness reflects the number of doublings undergone by megakaryocyte progenitors

Paulus, Jean‐Michel; Debili, Najet; Larbret, Frédéric; Levin, Jack; Vainchenker, William

doi:10.1182/blood-2003-05-1745

Cited by 9 publications

(9 citation statements)

References 44 publications

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“…This value is in agreement with a previous study of normal cells. 35 Altogether, these results confirmed that MPL-mutated PMFs are able to develop spontaneous megakaryocytic growth but that the dose response to TPO is not altered in MPL-mutated as well as in JAK2-mutated samples. …”

supporting

confidence: 69%

Evidence for MPL W515L/K mutations in hematopoietic stem cells in primitive myelofibrosis

Chaligné

James

Tonetti

et al. 2007

Blood

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IntroductionThe BCR-ABL-negative chronic myeloproliferative disorders (MPDs) include polycythemia vera (PV), essential thrombocytosis (ET), and primitive myelofibrosis (PMF). 1 These disorders are hematologic malignancies characterized by a clonal proliferation of one or several myeloid lineages. 2 PV, ET, PMF, and chronic myeloid leukemia (CML), defined as the classical MPDs, are considered to arise from the transformation of a multipotent hematopoietic stem cell. [3][4][5][6] However, the stem cell origin of the malignant clone had been demonstrated only in CML by the detection of either the characteristic t(9;22) translocation or the BCR/ABL transcript in all hematopoietic lineages. 7 More recently, detection of the JAK2 V617F mutation in a lympho/myeloid progenitor has been shown in some PV and PMF. 8 The JAK2 V617F mutation is found in almost all patients with PV, in 35% to 70% with ET, and in 50% with PMF. 9-13 Recently, we have detected the JAK2 V617F mutation in B and natural killer (NK) cells in approximately half of the PMF patients and in a minority of PV patients. Using the fetal thymus organ culture (FTOC) and B/NK/myeloid assays, we also have demonstrated that immature lympho/myeloid progenitors from PV and PMF carry the JAK2 V617F. 8 In 2006, 2 novel MPL somatic mutations (MPL W515L and MPL W515K) have been discovered in 5% and 1%, respectively, of JAK2 V617F-negative PMFs. The MPL W515L mutation confers to hematopoietic cells a cytokine-independent proliferation capacity, and results in a constitutive activation of JAK-STAT signaling. 14 The MPL W515K was later identified by sequencing granulocytes from 1182 MPD patients, but its precise effects on signaling are presently unknown. 15 W515 is the key amino acid located in a unique amphipathic domain that prevents spontaneous activation of MPL. 16 The substitution of W515 to an alanine or a serine has been shown to induce a factor-independent growth of the Ba/F3 cell line. 14,16 Therefore, it is expected that other amino acid changes in 515, such as the W515K, may induce a spontaneous MPL signaling.The growth factor-independent cellular proliferation of the megakaryocytic lineage was suggested to be based on the spontaneous homodimerization of MPL. [17][18][19][20][21][22] The viral oncogenic form of MPL, v-MPL, is characterized by the deletion of its extracellular domain. Its homodimerization results from the fusion of the truncated MPL sequence with the virus envelope. 18,23 Furthermore, introduction of a cysteine residue at codon 368 leads to a covalent disulfide-bonded homodimerization 19 and ligand-independent receptor activation. Similarly, the forced dimerization of MPL using monoclonal antibodies or the FK506-binding protein FKPB12 induces factor-independent proliferation. 24 W515 seems to play an important role in the prevention of basal MPL homodimerization. Indeed, the amphipathic domain of MPL, more precisely W515, prevents 2 receptors from coming close to each other in the absence of thrombopoietin (TPO). 16 In in vivo models, transpla...

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supporting

confidence: 69%

Evidence for MPL W515L/K mutations in hematopoietic stem cells in primitive myelofibrosis

Chaligné

James

Tonetti

et al. 2007

Blood

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“…In particular, TPO activates PI-3K, PKC, and MAPKinases thus determining the proliferation and differentiation of the MK lineage (Drachman et al, 1999;Kuter and Begley, 2002). Interestingly, TPO is able to induce the transition from mitosis and endomitosis with polyploidization of MK and platelets formation (Mintern et al, 1997;Paulus et al, 2004). By contrast, TPO is able to induce a discrete percentage of apoptotic cells during the MK cell proliferation/differentiation in cell line and primary cell cultures (Seoh et al, 1999;Ryu et al, 2001).…”

Section: Discussionmentioning

confidence: 92%

HIV‐1 negatively affects the survival/maturation of cord blood CD34+ hematopoietic progenitor cells differentiated towards megakaryocytic lineage by HIV‐1 gp120/CD4 membrane interaction

Gibellini¹,

Vitone²,

Buzzi³

et al. 2006

Journal Cellular Physiology

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To investigate the mechanisms involved in the human immunodeficiency virus type 1 (HIV-1)-related thrombocytopenia (TP), human umbilical cord blood (UCB) CD34(+) hematopoietic progenitor cells (HPCs) were challenged with HIV-1(IIIb) and then differentiated by thrombopoietin (TPO) towards megakaryocytic lineage. This study showed that HIV-1, heat-inactivated HIV-1, and HIV-1 recombinant gp120 (rgp120) activated apoptotic process of megakaryocyte (MK) progenitors/precursors and decreased higher ploidy MK cell fraction. All these inhibitory effects on MK survival/maturation and platelets formation were elicited by the interaction between gp120 and CD4 receptor on the cell membrane in the absence of HIV-1 productive infection. In fact, in our experimental conditions, HPCs were resistant to HIV-1 infection and no detectable productive infection was observed. We also evaluated whether the expression of specific cytokines, such as TGF-beta1 and APRIL, involved in the regulation of HPCs and MKs proliferation, was modulated by HIV-1. The specific protein and mRNA detection analysis, during TPO-induced differentiation, demonstrated that HIV-1 upregulates TGF-beta1 and downregulates APRIL expression through the CD4 engagement by gp120. Altogether, these data suggest that survival/differentiation of HPCs committed to MK lineage is negatively affected by HIV-1 gp120/CD4 interaction. This long-term inhibitory effect is also correlated to specific cytokines regulation and it may represent an additional mechanism to explain the TP occurring in HIV-1 patients.

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“…TPO was shown to support survival of very early HSC expressing low levels of the receptor, to trigger proliferation of progenitors that express high levels of Mpl and drive their more responsive progeny to terminal maturation (Paulus et al , 2004). Many studies have shown that TPO induces proliferation of CD34 + , CD41 + and CD34 + /CD41 + cells (Piacibello et al , 2000; Paulus et al , 2004; Kaushansky, 2005; Deutsch & Tomer, 2006), The addition of Flt‐ligand, IL‐6 and IL‐11 to TPO were shown to increase leucocyte expansion with differentiation and terminal maturation into the Mk lineage with high numbers of immature CD34 + CD41 + Mk progenitor cells reported (De Bruyn et al , 2005). Furthermore, engagement of the integrin‐α4β1, as is the case with FN enhances TPO‐induced megakaryopoiesis (Fox & Kaushansky, 2005).…”

Section: Discussionmentioning

confidence: 99%

Mimicking the haematopoietic niche microenvironment provides a novel strategy for expansion of haematopoietic and megakaryocyte‐progenitor cells from cord blood

et al. 2010

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SummarySevere neutropenia and protracted thrombocytopenia remain serious clinical problems following cord blood transplantation (CBT) due to the paucity of stem and progenitor cells in the grafts. Administration of ex-vivo expanded megakaryocyte progenitor cells may facilitate platelet production. We propose a novel strategy to expand these rare cells ex-vivo, from a small portion of the cord blood (CB) unit, using fibronectin (FN), a major component of hematopoietic niches, combined with cytokines, including thrombopoietin and the hematopoietic stress-associated acetylcholinesterase readthrough peptide (ARP). Application of multiple gates and high definition flow cytometry enabled clear resolution of expanded hematopoietic stem/ precursor cells (HSPC) and megakaryocyte progenitors (Mk-p) and their early subsets while eliminating positively stained non-relevant cells. FN increased viability, expansion of all CD34 + HSPC populations and Mk-p. The combination of FN + thrombopoietin + ARP maintained and expanded very early myeloid and thrombopoietic precursors, increased the proliferation of megakaryocyte, granulocyte-macrophage and multilineage colony-forming progenitors and supported Mk maturation as measured by ploidy and glycoprotein IIb/IIIa expression by quantiative reverse transcription polymerase chain reaction. This approach, which involves expanding HSPC and Mk precursors from a small portion of the CB unit, without sacrificing the coveted stem cells, may lead to improved cell therapy modalities to facilitate earlier myelopoiesis and platelet production post-CBT.

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Thrombopoietin responsiveness reflects the number of doublings undergone by megakaryocyte progenitors

Cited by 9 publications

References 44 publications

Evidence for MPL W515L/K mutations in hematopoietic stem cells in primitive myelofibrosis

Evidence for MPL W515L/K mutations in hematopoietic stem cells in primitive myelofibrosis

HIV‐1 negatively affects the survival/maturation of cord blood CD34+ hematopoietic progenitor cells differentiated towards megakaryocytic lineage by HIV‐1 gp120/CD4 membrane interaction

Mimicking the haematopoietic niche microenvironment provides a novel strategy for expansion of haematopoietic and megakaryocyte‐progenitor cells from cord blood

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