Search

Isocitrate dehydrogenase 1 (IDH1) is important for reductive carboxylation in cancer cells, and the IDH1 R132H mutation plays a pathogenic role in cancers including acute myeloid leukemia (AML). However, the regulatory mechanisms modulating mutant and/or wild-type (WT) IDH1 function remain unknown. Here, we show that two groups of tyrosine kinases (TK) enhance the activation of mutant and WT IDH1 through preferential Y42 or Y391 phosphorylation. Mechanistically, Y42 phosphorylation occurs in IDH1 monomers, which promotes dimer formation with enhanced substrate (isocitrate or α-ketoglutarate) binding, whereas Y42-phosphorylated dimers show attenuated disruption to monomers. Y391 phosphorylation occurs in both monomeric and dimeric IDH1, which enhances cofactor (NADP+ or NADPH) binding. Diverse oncogenic TKs phosphorylate IDH1 WT at Y42 and activate Src to phosphorylate IDH1 at Y391, which contributes to reductive carboxylation and tumor growth, whereas FLT3 or the FLT3-ITD mutation activates JAK2 to enhance mutant IDH1 activity through phosphorylation of Y391 and Y42, respectively, in AML cells. SIGNIFICANCE: We demonstrated an intrinsic connection between oncogenic TKs and activation of WT and mutant IDH1, which involves distinct TK cascades in related cancers. In particular, these results provide an additional rationale supporting the combination of FLT3 and mutant IDH1 inhibitors as a promising clinical treatment of mutant IDH1-positive AML.See related commentary by Horton and Huntly, p. 699.This article is highlighted in the In This Issue feature, p. 681.

Somatic mutations in the isocitrate dehydrogenase 2 gene (IDH2) contribute to the pathogenesis of acute myeloid leukaemia (AML) through the production of the oncometabolite 2-hydroxyglutarate (2HG).sup.1-8. Enasidenib (AG-221) is an allosteric inhibitor that binds to the IDH2 dimer interface and blocks the production of 2HG by IDH2 mutants.sup.9,10. In a phase I/II clinical trial, enasidenib inhibited the production of 2HG and induced clinical responses in relapsed or refractory IDH2-mutant AML.sup.11. Here we describe two patients with IDH2-mutant AML who had a clinical response to enasidenib followed by clinical resistance, disease progression, and a recurrent increase in circulating levels of 2HG. We show that therapeutic resistance is associated with the emergence of second-site IDH2 mutations in trans, such that the resistance mutations occurred in the IDH2 allele without the neomorphic R140Q mutation. The in trans mutations occurred at glutamine 316 (Q316E) and isoleucine 319 (I319M), which are at the interface where enasidenib binds to the IDH2 dimer. The expression of either of these mutant disease alleles alone did not induce the production of 2HG; however, the expression of the Q316E or I319M mutation together with the R140Q mutation in trans allowed 2HG production that was resistant to inhibition by enasidenib. Biochemical studies predicted that resistance to allosteric IDH inhibitors could also occur via IDH dimer-interface mutations in cis, which was confirmed in a patient with acquired resistance to the IDH1 inhibitor ivosidenib (AG-120). Our observations uncover a mechanism of acquired resistance to a targeted therapy and underscore the importance of 2HG production in the pathogenesis of IDH-mutant malignancies. A new mechanism of acquired clinical resistance in two patients with acute myeloid leukaemia driven by mutant IDH2 is described, in which a second-site mutation on the wild-type allele induces therapeutic resistance to IDH2 inhibitors., Author(s): Andrew M. Intlekofer [sup.1] [sup.2] [sup.3] [sup.4] , Alan H. Shih [sup.1] [sup.2] [sup.4] [sup.5] , Bo Wang [sup.1] [sup.2] [sup.6] , Abbas Nazir [sup.1] [sup.2] , Ariën S. [...]

Patients with myeloproliferative neoplasms (MPNs) frequently progress to bone marrow failure or acute myeloid leukemia (AML), and mutations in epigenetic regulators such as the metabolic enzyme isocitrate dehydrogenase (IDH) are associated with poor outcomes. Here, we showed that combined expression of [Jak2.sup.V617F] and mutant [IDH1.sup.R132H] or [Idh2.sup.R140Q] induces MPN progression, alters stem/progenitor cell function, and impairs differentiation in mice. [Jak2.sup.V617F] [Idh2.sup.R140Q]-mutant MPNs were sensitive to small-molecule inhibition of IDH. Combined inhibition of JAK2 and IDH2 normalized the stem and progenitor cell compartments in the murine model and reduced disease burden to a greater extent than was seen with JAK inhibition alone. In addition, combined JAK2 and IDH2 inhibitor treatment also reversed aberrant gene expression in MPN stem cells and reversed the metabolite perturbations induced by concurrent JAK2 and IDH2 mutations. Combined JAK2 and IDH2 inhibitor therapy also showed cooperative efficacy in cells from MPN patients with both [JAK2.sup.mut] and [IDH2.sup.mut] mutations. Taken together, these data suggest that combined JAK and IDH inhibition may offer a therapeutic advantage in this high-risk MPN subtype., Introduction Myeloproliferative neoplasms (MPNs) are clonal myeloid malignancies characterized by somatic mutations acquired in hematopoietic stem/progenitor cells, which drive the expansion of 1 or more myeloid lineages. Although patients with [...]

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by using the pluripotency factors Oct4, Sox2, Klf4 and c-Myc (together referred to as OSKM) (1). iPSC reprogramming erases somatic epigenetic signatures--as typified by DNA methylation or histone modification at silent pluripotency loci--and establishes alternative epigenetic marks of embryonic stem cells (ESCs) (2). Here we describe an early and essential stage of somatic cell reprogramming, preceding the induction of transcription at endogenous pluripotency loci such as Nanog and Esrrb.By day 4 after transduction with OSKM, two epigenetic modification factors necessary for iPSC generation, namely poly(ADP-ribose) polymerase-1 (Parp1) and ten-eleven translocation-2 (Tet2), are recruited to the Nanogand Esrrb loci. These epigenetic modification factors seem to have complementary roles in the establishment of early epigenetic marks during somatic cell reprogramming: Parp1 functions in the regulation of 5-methylcytosine (5mC) modification, whereas Tet2 is essential for the early generation of 5-hydroxymethylcytosine (5hmC) by the oxidation of 5mC (refs 3,4). Although 5hmC has been proposed to serve primarily as an intermediate in 5mC demethylation to cytosine in certain contexts (5-7), our data, and also studies of Tet2-mutant human tumour cells (8), argue in favour of a role for 5hmC as an epigenetic mark distinct from 5mC. Consistent with this, Parp1 and Tet2 are each needed for the early establishment of histone modifications that typify an activated chromatin state at pluripotency loci, whereas Parp1 induction further promotes accessibility to the Oct4 reprogramming factor. These findings suggest that Parp1 and Tet2 contribute to an epigenetic program that directs subsequent transcriptional induction at pluripotency loci during somatic cell reprogramming., We performed a functional screen for epigenetic modification factors that promote OSKM-mediated somatic cell reprogramming. Overexpression of a single pool of 29 candidate epigenetic modification factors, selected on the basis [...]

This paper describes a new efficient automatic remeshing method for three-dimensional hybrid meshes for viscous flow simulations to accommodate the meshes with changes of small devices quickly and easily. This remeshing method has two notable advantages. First, hybrid meshes can be generated automatically from a baseline mesh when the small devices are moved and/or deformed. This enables shape optimization techniques to find better models quickly, because tens or hundreds of meshes are usually required during the process. Second, the updated hybrid meshes are the same as the baseline mesh except for elements around the small devices. Their effect can be evaluated more accurately. Solution data from the baseline mesh can be shared with new hybrid meshes (e.g., as an initial condition to expedite the convergence of computational simulations). The remeshing method is applied to the Japan Aerospace Exploration Agency's high-lift-configuration standard model with a nacelle chine in different locations to demonstrate its capability. Computational simulations are also performed to further discuss the effectiveness of the remeshing method.

This paper describes the method to generate hybrid meshes composed of triangular prisms, pyramids, hexahedra, and tetrahedra for viscous computational fluid dynamics simulations. Surface triangulation is performed using a direct advancing front method or a modified mesh-decimation method. From a surface mesh, a near-field mesh is generated using an advancing layer approach. To generate high-quality meshes and to mesh around singular points, multiple marching directions are prepared from nodes on sharp convex corners. Special placement of elements around the sharp convex corners avoids using generalized elements. Tetrahedral meshing is then performed to fill the rest of the domain using an advancing front method. The hybrid mesh generation method is applied to several models to demonstrate its capability.