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:We present cell line SET-2 as potential model system for DNA methylation analysis. This cell line was established from a patient with essential thrombocythemia at megakaryoblastic transformation and carries the JAK2 V617F mutation. Cell line SET-2 carries the DNMT3A R882H mutation, recurrent in cytogenetically normal AML.
Project description:Myeloproliferative neoplasms (MPN) are a clonal hematological disease which harbors different driver mutations, including JAK2 V617F, and there is clear evidence that MPN is associated with aberrant DNA methylation (DNAm). However, it is unclear whether the driver mutation alone is sufficient to recapitulate the MPN phenotype and the global DNA methylation changes observed in patients. For this purpose, we utilized three established induced pluripotent stem cell (iPSC) clones carrying the JAK2 V617F mutation, both heterozygous and homozygous genotypes along with their wild type (WT) counterparts. These iPSCs were differentiated towards hematopoietic stem and progenitor differentiation (iHPCs) to capture the mutant phenotype. Genome wide methylation analysis of JAK2 mutated iPSCs and iHPCs showed no significant methylation differences compared to wild type cells. The iPSC model only partially recapitulated the DNAm changes observed in patients with JAK2 mutation, suggesting that epigenetic changes are not directly evoked by the driver mutation, but rather accumulate over the course of disease development.
Project description:To delineate the mechanism driving JAK2 inhibitors´ induced effects on HIV-1 latency, whole transcriptome profiling was performed in the HIV-1 latency model HL-HIG, treated with the LRA fedratinib, the LPA pacritinib, the pan-JAKi ruxolitinib and PMA as a positive control of latency reactivation and immune activation.
Project description:The activation of PD-1 (Programmed Death receptor-1) on T cells can cause T cell exhaustion and immune tolerance. Some tumors up-regulate the expression of the ligand of PD-1, namely PD-L1 (Programmed Death Receptor-Ligand 1), thus preventing anti-tumor immune response and promoting immune-escape. Previous studies have shown that JAK2 (Janus Kinase 2) signaling can promote PD-L1 expression in Hodgkin Lymphoma. In Myeloproliferative Neoplasms (MPN), JAK2 is frequently characterized by the the presence of the point-mutation V617F, which leads to its constitutive activation and to uncontrolled cell proliferation and survival. Accordingly, tumor cell lines expressing JAK2 V617F express higher levels of PD-L1 as compared to tumor cell lines negative for such mutations. In this experiment, we transfected BaF3 cells with a vector (plasmid for Murine Stem Cell Virus) containing the gene for JAK2 with the point-mutation V617F. As control, we used BaF3 cells transfected with the same vector, but without the gene for JAK2 V617F (empty vector). Both the cell lines (with/without JAK2 V617F) were co-cultured with primary murine T cells. When co-cultured with BaF3 cells expressing JAK2 V617F, T cells upregulated genes connected to senescence pathways, showed increased apoptosis, less cytokine production, and displayed other forms of dysfunction which can be associated with the activation of PD-1.
Project description:Hyperactivation of JAK2 kinase is a unifying feature of human Ph- myeloproliferative neoplasms (MPNs), most commonly due to the JAK2 V617F mutation. Mice harboring a homologous mutation in the Jak2 locus exhibit a phenotype resembling polycythemia vera. NFκB pathway hyperactivation is present in myeloid neoplasms, including MPNs, despite scarcity of mutations in NFκB pathway genes. To determine the impact of NFκB pathway hyperactivation in conjunction with Jak2 V617F, we utilized Ikk2 (Ikk2-CA) mice. Pan-hematopoietic Ikk2-CA alone produced depletion of hematopoietic stem cells and B cells. When combined with the Jak2 V617F mutation, Ikk2-CA rescued the polycythemia vera phenotype of Jak2 V617F. Likewise, Jak2 V617F ameliorated defects in hematopoiesis produced by Ikk2-CA. Single-cell RNA sequencing of hematopoietic stem and progenitor cells revealed multiple genes antagonistically regulated by Jak2 and Ikk2, including subsets whose expression was altered by Jak2 V617F and/or Ikk2-CA but partly or fully rectified in the double mutant. We hypothesize that Jak2 promotes hematopoietic stem cell population self-renewal, whereas Ikk2 promotes myeloid lineage differentiation, and biases cell fates at several branch points in hematopoiesis. Jak2 and Ikk2 both regulate multiple genes affecting myeloid maturation and cell death. Therefore, the presence of dual Jak2 and NFκB hyperactivation may present neomorphic therapeutic vulnerabilities in myeloid neoplasms.
Project description:Pegylated interferon alpha (pegIFNα) can induce molecular remissions in JAK2-V617F-positive myeloproliferative neoplasms (MPN) patients by targeting long-term hematopoietic stem cells (LT-HSCs). Additional somatic mutations in genes regulating LT-HSC self-renewal, such as DNMT3A, have been reported to have poorer responses to pegIFNα. We investigated if DNMT3A loss leads to alterations in JAK2-V617F LT-HSCs functions conferring resistance to pegIFNα treatment in a mouse model of MPN and in hematopoietic progenitors from MPN patients. Long-term treatment with pegIFNα normalized blood parameters, reduced splenomegaly and JAK2-V617F-chimerism in single-mutant JAK2-V617F (VF) mice. However, pegIFNα in VF;Dnmt3aΔ/Δ (VF;DmΔ/Δ) mice worsened splenomegaly and failed to reduce JAK2-V617F-chimerism. Furthermore, LT-HSCs from VF;DmΔ/Δ mice compared to VF were less prone to accumulate DNA damage and exit dormancy upon pegIFNα treatment. RNA-sequencing showed that IFNα induced stronger upregulation of inflammatory pathways in LT-HSCs from VF;DmΔ/Δ compared to VF mice, indicating that the resistance of VF;DmΔ/Δ LT-HSC was not due to failure in IFNα signaling. Transplantations of bone marrow from pegIFNα treated VF;DmΔ/Δ mice gave rise to more aggressive disease in secondary and tertiary recipients. Liquid cultures of hematopoietic progenitors from MPN patients with JAK2-V617F and DNMT3A mutation showed increased percentages of JAK2-V617F-positive colonies upon IFNα exposure, whereas in patients with JAK2-V617F alone the percentages of JAK2-V617F-positive colonies decreased or remained unchanged. PegIFNα combined with 5-azacytidine only partially overcame resistance in VF;DmΔ/Δ mice. However, this combination strongly decreased the JAK2-mutant allele burden in mice carrying VF mutation only, showing potential to inflict substantial damage preferentially to the JAK2-mutant clone.
Project description:In this dataset, we determine the global gene expression in human induced pluripotent stem (iPS) cell-derived CD61+ megakaryocytes carrying homozygous JAK2 V617F mutation or the JAK2 wildtype gene.
Project description:While PAX5 is an important tumor suppressor in B-ALL, it is also involved in oncogenic translocations coding for PAX5 fusion proteins. PAX5-JAK2 encodes a protein consisting of the PAX5 DNA-binding region fused to the constitutively active JAK2 kinase domain. Here, we studied the oncogenic function of PAX5-JAK2 in a mouse model expressing it from the endogenous Pax5 locus. The Pax5Jak2/+ mice rapidly developed an aggressive B-ALL in the absence of another cooperating mutation. The DNA-binding function and kinase activity of Pax5-Jak2, as well as IL-7 signaling, all contributed to leukemia development. Interestingly, all Pax5Jak2/+ tumors lost the wild-type Pax5 allele, allowing efficient DNA binding of Pax5-Jak2. While we could not find evidence for a nuclear role of Pax5-Jak2 as an epigenetic regulator, active phosphorylated Stat5 was present at a high level in Pax5Jak2/+ B-ALL tumors, consistent with increased expression of Stat5 target genes. Together, these data identified Pax5-Jak2 as an important nuclear driver of leukemia formation by maintaining phosphorylated Stat5 levels in the nucleus.