Loss of Ezh2 cooperates with Jak2V617F in the development of myelofibrosis in a mouse model of myeloproliferative neoplasm
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE79472 | GEO | 2016/04/19
SECONDARY ACCESSION(S): PRJNA315946
REPOSITORIES: GEO
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Project description:An activating JAK2V617F mutation has been found in ∼50% patients with myelofibrosis (MF). Inactivating mutations in histone methyltransferase enhancer of zeste homolog 2 (EZH2) also have been observed in patients with MF. Interestingly, inactivating EZH2 mutations are often associated with JAK2V617F mutation in MF, although their contributions in the pathogenesis of MF remain elusive. To determine the effects of concomitant loss of EZH2 and JAK2V617F mutation in hematopoiesis, we generated Ezh2-deficient Jak2V617F-expressing mice. Whereas expression of Jak2V617F alone induced a polycythemia vera-like disease, concomitant loss of Ezh2 significantly reduced the red blood cell and hematocrit parameters but increased the platelet counts in Jak2V617F knock-in mice. Flow cytometric analysis showed impairment of erythroid differentiation and expansion of megakaryocytic precursors in Ezh2-deficient Jak2V617F mice. Moreover, loss of Ezh2 enhanced the repopulation capacity of Jak2V617F-expressing hematopoietic stem cells. Histopathologic analysis revealed extensive fibrosis in the bone marrow (BM) and spleen of Ezh2-deleted Jak2V617F mice. Transplantation of BM from Ezh2-deleted Jak2V617F mice into wild-type animals resulted in even faster progression to MF. Gene expression profiling and chromatin immunoprecipitation sequence analysis revealed that S100a8, S100a9, Ifi27l2a, and Hmga2 were transcriptionally derepressed, and the H3K27me3 levels in these gene promoters were significantly reduced on Ezh2 deletion in hematopoietic progenitors of Jak2V617F mice. Furthermore, overexpression of S100a8, S100a9, Ifi27l2a, or Hmga2 significantly increased megakaryocytic colonies in the BM of Jak2V617F mice, indicating a role for these Ezh2 target genes in altered megakaryopoiesis involved in MF. Overall, our results suggest that loss of Ezh2 cooperates with Jak2V617F in the development of MF in Jak2V617F-expressing mice.
| S-EPMC4929929 | biostudies-literature
Project description:Loss of Ezh2 cooperates with Jak2V617F in the development of myelofibrosis in a mouse model of myeloproliferative neoplasm
| PRJNA315946 | ENA
Project description:Although Ras/mitogen-activated protein kinase (MAPK) signaling is activated in most human cancers, attempts to target this pathway using kinase-active site inhibitors have not typically led to durable clinical benefit. To address this shortcoming, we sought to test the feasibility of an alternative targeting strategy, focused on the ERK2 substrate binding domains, D and DEF binding pocket (DBP). Disabling the ERK2-DBP domain in mice caused baseline erythrocytosis. Consequently, we investigated the role of the ERK2-D and -DBP domains in disease, using a JAK2-dependent model of polycythemia vera (PV). Of note, inactivation of the ERK2-DBP domain promoted the progression of disease from PV to myelofibrosis, suggesting that the ERK2-DBP domain normally opposes progression. ERK2-DBP inactivation also prevented oncogenic JAK2 kinase (JAK2V617F) from promoting oncogene-induced senescence in vitro. The ERK2-DBP mutation attenuated JAK2-mediated oncogene-induced senescence by preventing the physical interaction of ERK2 with the transcription factor Egr1. Because inactivation of the ERK2-DBP created a functional ERK2 kinase limited to binding substrates through its D domain, these data suggested that the D domain substrates were responsible for promoting oncogene-induced progenitor growth and tumor progression and that pharmacologic targeting of the ERK2-D domain may attenuate cancer cell growth. Indeed, pharmacologic agents targeting the ERK2-D domain were effective in attenuating the growth of JAK2-dependent myeloproliferative neoplasm cell lines. Taken together, these data indicate that the ERK-D and -DBP domains can play distinct roles in the progression of neoplasms and that the D domain has the potential to be a potent therapeutic target in Ras/MAPK-dependent cancers.
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Project description:We studied non-driver mutations in 62 subjects with myeloproliferative neoplasm (MPN)-associated myelofibrosis upon diagnosis, including 45 subjects with primary myelofibrosis (PMF) and 17 with post-polycythemia vera or post-essential thrombocythemia myelofibrosis (post-PV/ET MF). Fifty-eight subjects had ?1 non-driver mutation upon diagnosis. Mutations in mRNA splicing genes, especially in U2AF1, were significantly more frequent in PMF than in post-PV/ET MF (33 vs. 6%; P?=?0.015). There were also striking differences in clonal architecture. These data indicate different genomic spectrums between PMF and post-PV/ET MF.
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Project description:Megakaryocytes (MKs) is an important component of the hematopoietic niche. Abnormal MK hyperplasia is a hallmark feature of myeloproliferative neoplasms (MPNs). The JAK2V617F mutation is present in hematopoietic cells in a majority of patients with MPNs. Using a murine model of MPN in which the human JAK2V617F gene is expressed in the MK lineage, we show that the JAK2V617F-bearing MKs promote hematopoietic stem cell (HSC) aging, manifesting as myeloid-skewed hematopoiesis with an expansion of CD41+ HSCs, a reduced engraftment and self-renewal capacity, and a reduced differentiation capacity. HSCs from 2-year-old mice with JAK2V617F-bearing MKs were more proliferative and less quiescent than HSCs from age-matched control mice. Examination of the marrow hematopoietic niche reveals that the JAK2V617F-bearing MKs not only have decreased direct interactions with hematopoietic stem/progenitor cells during aging but also suppress the vascular niche function during aging. Unbiased RNA expression profiling reveals that HSC aging has a profound effect on MK transcriptomic profiles, while targeted cytokine array shows that the JAK2V617F-bearing MKs can alter the hematopoietic niche through increased levels of pro-inflammatory and anti-angiogenic factors. Therefore, as a hematopoietic niche cell, MKs represent an important connection between the extrinsic and intrinsic mechanisms for HSC aging.
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Project description:Arterial cardiovascular events are the leading cause of death in patients with JAK2V617F myeloproliferative neoplasms (MPNs). However, their mechanisms are poorly understood. The high prevalence of myocardial infarction without significant coronary stenosis or atherosclerosis in patients with MPNs suggests that vascular function is altered. The consequences of JAK2V617F mutation on vascular reactivity are unknown. We observe here increased responses to vasoconstrictors in arteries from Jak2V617F mice resulting from a disturbed endothelial NO pathway and increased endothelial oxidative stress. This response was reproduced in WT mice by circulating microvesicles isolated from patients carrying JAK2V617F and by erythrocyte-derived microvesicles from transgenic mice. Microvesicles of other cellular origins had no effect. This effect was observed ex vivo on isolated aortas, but also in vivo on femoral arteries. Proteomic analysis of microvesicles derived from JAK2V617F erythrocytes identified increased expression of myeloperoxidase as the likely mechanism accounting for their effect. Myeloperoxidase inhibition in microvesicles derived from JAK2V617F erythrocytes suppressed their effect on oxidative stress. Antioxidants such as simvastatin and N-acetyl cysteine improved arterial dysfunction in Jak2V617F mice. In conclusion, JAK2V617F MPNs are characterized by exacerbated vasoconstrictor responses resulting from increased endothelial oxidative stress caused by circulating erythrocyte-derived microvesicles. Simvastatin appears to be a promising therapeutic strategy in this setting.
| S-EPMC7190923 | biostudies-literature
Project description:Myeloproliferative neoplasm (MPN) patients frequently show co-occurrence of JAK2-V617F and mutations in epigenetic regulator genes, including EZH2 In this study, we show that JAK2-V617F and loss of Ezh2 in hematopoietic cells contribute synergistically to the development of MPN. The MPN phenotype induced by JAK2-V617F was accentuated in JAK2-V617F;Ezh2(-/-) mice, resulting in very high platelet and neutrophil counts, more advanced myelofibrosis, and reduced survival. These mice also displayed expansion of the stem cell and progenitor cell compartments and a shift of differentiation toward megakaryopoiesis at the expense of erythropoiesis. Single cell limiting dilution transplantation with bone marrow from JAK2-V617F;Ezh2(+/-) mice showed increased reconstitution and MPN disease initiation potential compared with JAK2-V617F alone. RNA sequencing in Ezh2-deficient hematopoietic stem cells (HSCs) and megakaryocytic erythroid progenitors identified highly up-regulated genes, including Lin28b and Hmga2, and chromatin immunoprecipitation (ChIP)-quantitative PCR (qPCR) analysis of their promoters revealed decreased H3K27me3 deposition. Forced expression of Hmga2 resulted in increased chimerism and platelet counts in recipients of retrovirally transduced HSCs. JAK2-V617F-expressing mice treated with an Ezh2 inhibitor showed higher platelet counts than vehicle controls. Our data support the proposed tumor suppressor function of EZH2 in patients with MPN and call for caution when considering using Ezh2 inhibitors in MPN.
| S-EPMC4986524 | biostudies-literature
Project description:Although the pathogenesis of primary myelofibrosis (PMF) and other myeloproliferative neoplasms (MPNs) is linked to constitutive activation of the JAK-STAT pathway, JAK inhibitors have neither curative nor MPN-stem cell-eradicating potential, indicating that other targetable mechanisms are contributing to the pathophysiology of MPNs. We previously demonstrated that Abelson interactor 1 (Abi-1), a negative regulator of Abelson kinase 1, functions as a tumor suppressor. Here we present data showing that bone marrow-specific deletion of Abi1 in a novel mouse model leads to development of an MPN-like phenotype resembling human PMF. Abi1 loss resulted in a significant increase in the activity of the Src family kinases (SFKs), STAT3, and NF-κB signaling. We also observed impairment of hematopoietic stem cell self-renewal and fitness, as evidenced in noncompetitive and competitive bone marrow transplant experiments. CD34+ hematopoietic progenitors and granulocytes from patients with PMF showed decreased levels of ABI1 transcript as well as increased activity of SFKs, STAT3, and NF-κB. In aggregate, our data link the loss of Abi-1 function to hyperactive SFKs/STAT3/NF-κB signaling and suggest that this signaling axis may represent a regulatory module involved in the molecular pathophysiology of PMF.
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Project description:IntroductionThe Janus kinase (JAK)1/2 inhibitor ruxolitinib provides rapid, sustained and often dramatic benefits to patients with myelofibrosis, inducing spleen shrinkage and ameliorating symptoms, and improves survival. However, the drug has little effect on the underlying bone marrow fibrosis or on mutant allele burden, and clinical resistance eventually develops. Furthermore, ruxolitinib-induced cytopenias can be challenging in everyday practice.Areas coveredThe developmental therapeutics landscape in MF is discussed. This includes potential partners for ruxolitinib being developed with an aim to improve cytopenias, or to enhance its disease-modifying effects. The development of other JAK inhibitors with efficacy post-ruxolitinib or other unique attributes is being pursued in earnest. Agents with novel mechanisms of action are being studied in patients whose disease responds sub-optimally to, is refractory to or progresses after ruxolitinib.Expert opinionThe JAK inhibitors fedratinib, pacritinib and momelotinib are clearly active, and it is expected that one or more of these will become licensed in the future. The activin receptor ligand traps are promising as treatments for anemia. Imetelstat has shown interesting activity post-ruxolitinib, and azactidine may be a useful partner for ruxolitinib in some patients. Appropriately, multiple pre-clinical and clinical leads are being pursued in this difficult therapeutic area.
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Project description:Interferon-? (IFN?) is an effective treatment of patients with myeloproliferative neoplasms (MPNs). In addition to inducing hematological responses in most MPN patients, IFN? 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 IFN? on JAK2V617F mutant stem cells is debated. Using a murine model of Jak2V617F MPN, we investigated the effects of IFN? on Jak2V617F MPN-propagating stem cells in vivo. We report that IFN? treatment induces hematological responses in the model and causes depletion of Jak2V617F MPN-propagating cells over time, impairing disease transplantation. We demonstrate that IFN? treatment induces cell cycle activation of Jak2V617F mutant long-term hematopoietic stem cells and promotes a predetermined erythroid-lineage differentiation program. These findings provide insights into the differential effects of IFN? on Jak2V617F mutant and normal hematopoiesis and suggest that IFN? 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 IFN? and targeting the proliferating downstream progeny with JAK2 inhibitors or cytotoxic chemotherapy.
| S-EPMC3643767 | biostudies-literature