ABSTRACT: Physiological Jak2V617F expression causes a lethal myeloproliferative neoplasm with differential effects on hematopoietic stem and progenitor cells
Project description:Estrogens are potential regulators of the hematopoietic stem cell (HSC) niche and have effects on mature hematopoietic cells; however, whether estrogen signaling directly regulates normal and malignant HSC remains unclear. We demonstrate differential expression and specific roles of estrogen receptors (ER) in hematopoietic progenitors. ERa activation in short-term HSC and multipotent progenitors induced apoptosis. In contrast, the selective ER modulator (SERM) tamoxifen induced proliferation of quiescent long-term HSC, altered their self-renewal signature and compromised hematopoietic reconstitution following myelotoxic stress. Treatment with tamoxifen alone abolished hematopoietic progenitor expansion induced by JAK2V617F by restoring normal levels of apoptosis, blocked JAK2V617F-induced myeloproliferative neoplasm in vivo, and sensitized MLL-AF9+ leukemias to chemotherapy. Tamoxifen showed selective effects on mutant cells compared to normal ones, and had only a minor impact on steady-state hematopoiesis in disease-free animals. These results uncover specific regulation of hematopoietic progenitors by estrogens and potential anti-leukemic properties of SERM LT-HSCs, ST-HSCs and MPPs sorted from the bone marrow of mice treated with tamoxifen or vehicle (3 biological replicates per group)
Project description:Estrogens are potential regulators of the hematopoietic stem cell (HSC) niche and have effects on mature hematopoietic cells; however, whether estrogen signaling directly regulates normal and malignant HSC remains unclear. We demonstrate differential expression and specific roles of estrogen receptors (ER) in hematopoietic progenitors. ERa activation in short-term HSC and multipotent progenitors induced apoptosis. In contrast, the selective ER modulator (SERM) tamoxifen induced proliferation of quiescent long-term HSC, altered their self-renewal signature and compromised hematopoietic reconstitution following myelotoxic stress. Treatment with tamoxifen alone abolished hematopoietic progenitor expansion induced by JAK2V617F by restoring normal levels of apoptosis, blocked JAK2V617F-induced myeloproliferative neoplasm in vivo, and sensitized MLL-AF9+ leukemias to chemotherapy. Tamoxifen showed selective effects on mutant cells compared to normal ones, and had only a minor impact on steady-state hematopoiesis in disease-free animals. These results uncover specific regulation of hematopoietic progenitors by estrogens and potential anti-leukemic properties of SERM
Project description:Background: Cancers result from accumulation of somatic mutations and their properties are thought to reflect the sum of these mutations. However, little is known about the consequences of altering the order of mutation acquisition. Methods: Mutation order was determined in myeloproliferative neoplasm patients by genotyping hematopoietic colonies or next generation sequencing. Stem and progenitor cells were isolated to study the effect of mutation order on mature and immature hematopoietic cells. Results: Age of presentation, acquisition of JAK2V617F homozygosity and the balance of immature progenitors were all influenced by mutation order. Compared to TET2-first patients, JAK2-first patients had an increased likelihood of presenting with polycythemia vera than essential thrombocythemia, an increased risk of thrombosis and an increased sensitivity of JAK2-mutant progenitors to ruxolitinib in vitro. In studies of single hematopoietic stem and progenitor cells (HSPCs), mutation order influenced the proliferative response to JAK2V617F and the capacity of double-mutant HSPCs to generate colony-forming cells. Moreover the HSPC compartment was dominated by TET2 single-mutant cells in TET2-first patients but by JAK2/TET2 double-mutant cells in JAK2-first patients. Prior mutation of TET2 altered the transcriptional consequences of JAK2V617F in a cell-intrinsic manner, and prevented JAK2V617F from up-regulating genes associated with proliferation. These data demonstrate that mutation order influences progenitor proliferation and terminal cell expansion, thus influencing clinical presentation, thrombosis risk and progenitor response to targeted therapy. Conclusions: The order in which JAK2 and TET2 mutations are acquired influences clinical features, stem/progenitor cell biology and clonal evolution in patients with myeloproliferative neoplasms.
Project description:V617F driver mutation of JAK2 is the leading cause of the Philadelphia-chromosome-negative myeloproliferative neoplasms (MPNs). Loss of Plek2 ameliorated JAK2V617F-induced myeloproliferative phenotypes including erythrocytosis, neutrophilia, thrombocytosis, and splenomegaly, thereby reverting the widespread vascular occlusions and lethality of JAK2V617F knockin mice. To reveal the role of Plek2 in the pathogenesis of JAK2V617F-induced MPNs and the detail mechanisms of its rescue, we performed RNA sequencing to analyze the gene expression profiles change between JAK2V617F/+ Plek2+/+ and JAK2V617F/+ Plek2-/- erythroblasts and hematopoietic stem/progenitor cells.
Project description:Interferon alpha (IFNa) is an effective treatment for patients with myeloproliferative neoplasms (MPN). In addition to inducing hematological responses in most MPN patients, IFNa reduces the JAK2V617F allelic burden and can render the JAK2V617F mutant clone undetectable in some patients. The precise mechanism underlying these responses is incompletely understood and whether the molecular responses that are seen occur due to the effects of IFNa on JAK2V617F mutant stem cells is debated. Using a murine model of Jak2V617F MPN, we investigated the effects of IFNa on Jak2V617F MPN-propagating stem cells in vivo. We report that IFNa treatment induces hematological responses in the model and causes depletion of Jak2V617F MPN-propagating cells over time, impairing disease transplantation. We demonstrate that IFNa treatment induces cell-cycle activation of Jak2V617F mutant long-term hematopoietic stem cells (LT-HSC) and promotes a predetermined erythroid-lineage differentiation program. These findings provide insights into the differential effects of IFNa on Jak2V617F mutant and normal hematopoiesis and suggest that IFNa achieves molecular remissions in MPN patients through its effects on MPN stem cells. Furthermore, these results support combinatorial therapeutic approaches in MPN, by concurrently depleting dormant JAK2V617F MPN-propagating stem cells with IFNa and targeting the proliferating downstream progeny with JAK2-inhibitors or cytotoxic chemotherapy. HSC-enriched population from WT (CD45.1) or Jak2VF knockin (CD45.2), after 4 weeks of interferon alpha or vehicle treatment. N=4 per condition
Project description:We report a Jak2V617F knock-in mouse myeloproliferative neoplasm (MPN) model resembling human polycythemia vera (PV). The MPN is serially transplantable and we demonstrate that the hematopoietic stem cell (HSC) compartment has the unique capacity for disease initiation but does not have a selective competitive advantage over wild type HSCs. In contrast, myeloid progenitor populations are expanded and skewed towards the erythroid lineage, but cannot transplant the disease. Treatment with a JAK2 kinase inhibitor ameliorated the MPN phenotype, but did not eliminate the disease-initiating population. These findings provide insights into the consequences of JAK2 activation on HSC differentiation and function and have the potential to inform therapeutic approaches to JAK2V617F positive MPN. LKS cells were isolated from wild type (n=4) and JAK2V617F mutant mice (n=4). RNA was extracted using Qiagen RNeasy Micro Kit according to manufacturers instruction and amplified using NUGEN amplification kit. cDNA was fragmented and biotinylated before hybridization onto Affymetrix Mouse Expression Array 430 2.0.
Project description:We report a Jak2V617F knock-in mouse myeloproliferative neoplasm (MPN) model resembling human polycythemia vera (PV). The MPN is serially transplantable and we demonstrate that the hematopoietic stem cell (HSC) compartment has the unique capacity for disease initiation but does not have a selective competitive advantage over wild type HSCs. In contrast, myeloid progenitor populations are expanded and skewed towards the erythroid lineage, but cannot transplant the disease. Treatment with a JAK2 kinase inhibitor ameliorated the MPN phenotype, but did not eliminate the disease-initiating population. These findings provide insights into the consequences of JAK2 activation on HSC differentiation and function and have the potential to inform therapeutic approaches to JAK2V617F positive MPN.
Project description:Interferon alpha (IFNa) is an effective treatment for patients with myeloproliferative neoplasms (MPN). In addition to inducing hematological responses in most MPN patients, IFNa reduces the JAK2V617F allelic burden and can render the JAK2V617F mutant clone undetectable in some patients. The precise mechanism underlying these responses is incompletely understood and whether the molecular responses that are seen occur due to the effects of IFNa on JAK2V617F mutant stem cells is debated. Using a murine model of Jak2V617F MPN, we investigated the effects of IFNa on Jak2V617F MPN-propagating stem cells in vivo. We report that IFNa treatment induces hematological responses in the model and causes depletion of Jak2V617F MPN-propagating cells over time, impairing disease transplantation. We demonstrate that IFNa treatment induces cell-cycle activation of Jak2V617F mutant long-term hematopoietic stem cells (LT-HSC) and promotes a predetermined erythroid-lineage differentiation program. These findings provide insights into the differential effects of IFNa on Jak2V617F mutant and normal hematopoiesis and suggest that IFNa achieves molecular remissions in MPN patients through its effects on MPN stem cells. Furthermore, these results support combinatorial therapeutic approaches in MPN, by concurrently depleting dormant JAK2V617F MPN-propagating stem cells with IFNa and targeting the proliferating downstream progeny with JAK2-inhibitors or cytotoxic chemotherapy.
Project description:DNMT3A mutations are observed in myeloid malignancies, including myeloproliferative neoplasms (MPN), myelodysplastic syndromes (MDS), and acute myeloid leukemia (AML). Here we investigated the impact of conditional hematopoietic Dnmt3a loss on disease phenotype in primary mice. Dnmt3a ablation led to a lethal, fully penetrant myeloproliferative neoplasm with myelodysplasia (MDS/MPN) characterized by marked, progressive hepatomegaly that was transplantable. We detected expanded stem/progenitor populations in the liver of Dnmt3a-ablated mice. Homing studies showed that Dnmt3a-deleted bone marrow cells preferentially migrated to the liver. Hence, in addition to the established role of Dnmt3a in regulating self-renewal, Dnmt3a regulates tissue tropism and limits myeloid progenitor expansion in vivo.
Project description:DNMT3A mutations are observed in myeloid malignancies, including myeloproliferative neoplasms (MPN), myelodysplastic syndromes (MDS), and acute myeloid leukemia (AML). Here we investigated the impact of conditional hematopoietic Dnmt3a loss on disease phenotype in primary mice. Dnmt3a ablation led to a lethal, fully penetrant myeloproliferative neoplasm with myelodysplasia (MDS/MPN) characterized by marked, progressive hepatomegaly that was transplantable. We detected expanded stem/progenitor populations in the liver of Dnmt3a-ablated mice. Homing studies showed that Dnmt3a-deleted bone marrow cells preferentially migrated to the liver. Hence, in addition to the established role of Dnmt3a in regulating self-renewal, Dnmt3a regulates tissue tropism and limits myeloid progenitor expansion in vivo.