Project description:Transcriptional profiling of transformed Ba/F3 cells by myeloproliferative neoplasm-associated JAK2 V617F mutant comparing control Ba/F3 cells expressing wild type JAK2. Two-condition experiment, WT cells vs. VF cells. One replicate per array.
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:SPAG9-JAK2 is a novel fusion gene identified in a pediatric patient with Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL). In this study, we performed functional analysis of the SPAG9-JAK2 fusion to establish molecular targeted therapy. Ba/F3 cells expressing SPAG9-JAK2 generated by retroviral transduction (Ba/F3-SPAG9-JAK2), proliferated in the absence of IL-3, and exhibited constitutive phosphorylation of the tyrosine residues in the JAK2 kinase domain of the fusion protein and STAT3/STAT5. Mutation of tyrosine residues in the JAK2 kinase domain (SPAG9-JAK2 mut) abolished IL-3 independence, but had no influence on STAT3/STAT5 phosphorylation levels. Gene expression analysis revealed that Stat1 was significantly up-regulated in Ba/F3-SPAG9-JAK2 cells. STAT1 was also phosphorylated in Ba/F3-SPAG9-JAK2 but not SPAG9-JAK2 mut cells, suggesting that STAT1 is key for SPAG9-JAK2-mediated cell proliferation. Consistently, STAT1 induced expression of the anti-apoptotic proteins, BCL-2 and MCL-1, as did SPAG9-JAK2, but not SPAG9-JAK2 mut. Ruxolitinib abrogated Ba/F3-SPAG9-JAK2-mediated proliferation in vitro, but was insufficient in vivo. Venetoclax (a BCL-2 inhibitor) or AZD5991 (an MCL-1 inhibitor) enhanced the effects of ruxolitinib on Ba/F3-SPAG9-JAK2 in vitro. These findings suggest that activation of the JAK2-STAT1-BCL-2/MCL-1 axis contributes to SPAG9-JAK2-related aberrant growth promotion. BCL-2 or MCL-1 inhibition is a potential therapeutic option for B-ALL with SPAG9-JAK2 fusion.
Project description:JAK2-V617F is the most frequent somatic mutation causing myeloproliferative neoplasm (MPN). JAK2-V617F can be found in healthy individuals with clonal hematopoiesis of indeterminate potential (CHIP) with a frequency much higher than the prevalence of MPN. The factors controlling the conversion of JAK2-V617F CHIP to MPN are largely unknown. We hypothesized that IL-1β mediated inflammation can favor this progression. We established an experimental system using bone marrow (BM) transplantations from JAK2-V617F and GFP transgenic (VF;GFP) mice, that were further crossed with IL-1β-/- or IL-1R1-/- mice. To study the role of IL-1β and its receptor on monoclonal evolution of MPN, we performed competitive BM transplantations at high dilutions with only 1-3 hematopoietic stem cells (HSCs) per recipient. Loss of IL-1β in JAK2-mutant HSCs reduced engraftment, restricted clonal expansion, lowered the total numbers of functional HSCs, and decreased the rate of conversion to MPN. Loss of IL-1R1 in the recipients also lowered the conversion to MPN, but did not reduce the frequency of engraftment of JAK2-mutant HSCs. WT recipients transplanted with VF;GFP BM that developed MPN had elevated IL-1β levels and reduced frequencies of mesenchymal stromal cells (MSCs). Interestingly, frequencies of MSCs were also reduced in recipients that did not develop MPN, had only marginally elevated IL-1β levels and displayed low GFP-chimerism resembling CHIP. Anti-IL-1β antibody preserved high frequencies of MSCs in VF;GFP recipients and reduced the rate of engraftment and the conversion to MPN. Our results identify IL-1β as a potential therapeutic target for preventing the transition from JAK2-V617F CHIP to MPN.
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:Transplant recipients of IDH2-R140Q JAK2-V617F expressing bone marrow were treated with AG221 and ruxolitinib monotherapy, combined therapy, or vehicle. LSKs were sorted from terminal samples and sequenced with three WT controls.
Project description:Ruxolinitib was approved by the FDA for the treatment of JAK2-V617F positive myelofibrosis. Unexpectedly, treatment of JAK2-V617F expressing cells with ruxolitinib causes paradoxical hyperphosphorylation of JAK2 at Tyr1007/1008 sites. The mechanism of ruxolitinib-induced JAK2 hyperphosphorylation is not well understood. A ruxolitinib-resistant JAK2 variant (V617F+L983F) and a JAK2-V617F kinase dead mutant (JAK2-V617F+K882R) did not show paradox hyperphosphorylation after ruxolitinib treatment indicating that ruxolitinib-mediated JAK2 hyperphosphorylation is mediated by a JAK2 intrinsic mechanism. Native immunocomplexes of JAK2-V617F with an antibody against pTyr1007/1008 could be blocked by the presence of ruxolitinib, although JAK2-V617F was hyperphosphorylated at these sites, suggesting that in the presence of ruxolitinib the JAK2 activation loop is buried within the kinase domain. This stabilization of the activation loop conformation results in the protection of pTyr1007/1008 sites from phosphatases. When JAK2 is in an inhibited conformationally restricted state, the phosphate group of Tyr1007 and Tyr1008 forms an intermolecular interaction with Arg975 and Lys999, respectively. Mutation of Arg975 and Lys999 to Ala reduced the phosphorylation at both Tyr1007/1008 residues, and importantly, ruxolitinib treatment did not lead to JAK2 hyperphosphorylation in these variants. Hyperphosphorylated JAK2 is hyperactive after ruxolitinib dissociation and activates STAT5 target genes PIM2, ID1, and MPL. Our results suggest a novel mode of kinase regulation by modulating kinase activity through conformational changes induced by ruxolitinib.
Project description:Gene expression profiles in Ba/F3 cells expressing ETV6-PDGFRB, FIP1L1-PDGFRA or a control vector, treated or not with imatinib (Glivec) Ba/F3 cells expressing FIP1L1-PDGFRA or ETV6-PDGFRB were cultured in the presence or absence of imatinib for 4 hours before RNA extraction followed by hybridization on Affymetrix microarrays. In a control condition Ba/F3 cells were cultured in the presence of IL3 in the absence or in the presence of imatinib for 4 hours before RNA extraction. 4 hours treatment with imatinib in Ba/F3 cells expressing ETV6-PDGFRB, FIP1L1-PDGFRA or a control vector