The pathophysiology of type 1 versus type 2 mutant calreticulin-drivenmyeloproliferative neoplasms

1 型与 2 型突变钙网蛋白驱动的骨髓增殖性肿瘤的病理生理学

• 批准号: 10503876
• 负责人: Shannon Elisabeth Elf
• 金额: $ 49.61万
• 依托单位: UNIVERSITY OF CHICAGO
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10503876
• 关键词: ATF6 gene; Acute Myelocytic Leukemia; Anabolism; Base Pairing; Binding; Binding Sites; Blood Platelets; Bone Marrow; Bone remodeling; C-terminal; Calcium; Calcium Binding; Carbon; Cell Compartmentation; Cell Death; Cell Survival; Cells; Cellular Stress Response; Code; Collagen; Data; Deposition; Development; Disease; Disease Progression; Endoplasmic Reticulum; Erythrocytes; Etiology; Exhibits; Exons; Fibrosis; Functional disorder; Genes; Glycine; Hematocrit procedure; Hematopoietic; Hematopoietic Stem Cell Transplantation; Hemoglobin; Hemorrhagic Thrombocythemia; In Vitro; Incidence; Inflammation; Inflammatory; Interleukin-6; JAK2 gene; Lead; MPL gene; Mediating; Megakaryocyte Proliferation; Megakaryocytes; Metabolism; Molecular; Molecular Abnormality; Molecular Chaperones; Morbidity - disease rate; Mutation; Myeloid Cells; Myeloproliferative disease; Neoplasms; Pathogenicity; Pathway interactions; Patients; Peptides; Phenotype; Polycythemia Vera; Primary Myelofibrosis; Production; Prognosis; Proteins; Risk; Role; Serine; Signal Transduction; Somatic Mutation; Stromal Cells; Survival Rate; Testing; Up-Regulation; XBP1 gene; arm; base; calreticulin; cancer cell; cell type; clinical phenotype; curative treatments; cytokine; disease phenotype; driver mutation; endoplasmic reticulum stress; granulocyte; in vivo; individualized medicine; inhibitor; loss of function; mortality; mutant; novel; prognostic; proteostasis; response; sensor; stem cells; stressor; targeted treatment; therapeutic target; transcription factor; treatment strategy

Project Summary Myeloproliferative neoplasms (MPNs) include primary myelofibrosis (PMF; characterized by the over- proliferation of megakaryocytes and granulocytes with abnormal collagen deposition in the bone marrow stroma), essential thrombocythemia (ET; increased megakaryocyte and platelet production), and polycythemia vera (PV; increased red cell production, hemoglobin, and hematocrit). Although all MPN driver mutations lead to constitutive activation of JAK/STAT signaling, targeted JAK inhibitors are not curative and fail to alter disease progression. Therefore, there is a great unmet need to identify novel curative therapies for MPNs. Mutations in calreticulin (CALR) represent the second most common genetic abnormality in MPN. The CALR gene encodes a calcium (Ca2+)-binding chaperone protein that primarily resides in the endoplasmic reticulum (ER). All CALR mutations share an identical neomorphic C-terminal peptide, which permits binding to the thrombopoietin receptor MPL and the subsequent activation of pathogenic JAK/STAT signaling. The majority of CALR mutations are classified as either type 1 or type 2 based on the extent of homology to the wild type protein, where type 1 proteins exhibit complete loss of C-terminal Ca2+ binding sites that are retained in type 2. Despite their shared mutant C-terminus and ability to bind and activate MPL, type 1 and 2 CALR mutations engender significant phenotypic and prognostic differences. Type 1 mutations are more common in PMF, and are associated with increased risk of myelofibrotic transformation from ET. Conversely, type 2 mutations are primarily associated with ET, exhibit low incidence of myelofibrotic transformation, and are rarely found in PMF. The mechanisms underlying these divergent clinical phenotypes remain unknown. We discovered that the IRE1a/XBP1 pathway of the unfolded protein response (UPR) is differentially activated in type 1 versus type 2 mutant CALR cells, and that type 1 mutant CALR cells are dependent on this pathway for survival and to drive ET. We found that IRE1a/XBP1 is activated only by type 1 and not type 2 mutant CALR due to a loss of calcium binding function specific to the type 1 protein. More recently, we found that the ATF6 pathway of the UPR is differentially up- regulated in type 2 compared to type 1 mutant CALR cells, and that type 2 mutant proteins exhibit loss of molecular chaperone function. These data support the central hypothesis that type 1 and type 2 CALR mutations activate and depend on different arms of the UPR based on their respective losses of function, and that these pathways promote distinct disease phenotypes. Thus, targeting different arms of the UPR based on mutation type may represent a novel, individualized treatment strategy for type 1 versus type 2 CALR+ MPN patients. To test this hypothesis, we will dissect the role of the UPR in type 1 mutant CALR-driven fibrosis (Specific Aim 1) and type 2 mutant CALR-driven ET (Specific Aim 2), and determine if each is uniquely sensitive to therapeutic targeting of different arms of the UPR (Specific Aim 3).

项目摘要 骨髓增生性肿瘤(MPN)包括原发性骨髓纤维化(PMF)，其特征是过度的 骨髓基质中有异常胶原沉积的巨核细胞和粒细胞的增殖)， 原发性血小板增多症(ET；巨核细胞和血小板生成增加)和真性红细胞增多症(PV； 增加红细胞生成、血红蛋白和红细胞压积)。尽管所有MPN驱动程序突变都会导致 JAK/STAT信号的结构性激活，靶向JAK抑制剂不能治愈，也不能改变疾病 进步。因此，寻找治疗MPN的新疗法是一个尚未得到满足的巨大需求。基因突变 钙网蛋白(CALR)是MPN中第二常见的遗传异常。CALR基因编码 一种钙(钙)结合的伴侣蛋白，主要存在于内质网(ER)。所有CALR 突变共享一个相同的新构型C末端多肽，它允许与血小板生成素结合 受体MPL和随后的致病JAK/STAT信号的激活。大多数CALR突变 根据与野生型蛋白的同源性程度分为类型1或类型2，其中类型1 蛋白质表现出完全失去了保留在2型中的C末端钙结合位点。尽管它们有共同的 突变的C末端以及结合和激活MPL、1型和2型CALR突变的能力 表型和预后差异。1型突变在PMF中更常见，并与 ET导致骨髓纤维化转化的风险增加。相反，2型突变主要与 ET患者的骨髓纤维化转化发生率较低，在PMF中少见。其作用机制 这些不同的临床表型背后的原因尚不清楚。我们发现IRE1a/XBP1途径 在1型突变的CALR细胞和2型突变的CALR细胞中，未折叠蛋白反应(UPR)的活性存在差异 1型突变型CALR细胞依赖于这一途径生存和驱动ET。我们发现 由于钙结合功能的丧失，IRE1a/XBP1仅被1型而不是2型突变体CALR激活 特异性的类型1蛋白。最近，我们发现UPR的ATF6通路差异地向上- 与类型1突变的CALR细胞相比，在类型2中调节，并且类型2突变蛋白表现出丢失 分子伴侣功能。这些数据支持类型1和类型2 CALR的中心假设 突变根据其各自的功能丧失而激活并依赖于UPR的不同手臂，以及 这些途径促进了不同的疾病表型。因此，以普遍定期审议的不同部门为目标 突变类型可能代表了1型与2型CALR+MPN的一种新的个体化治疗策略 病人。为了验证这一假设，我们将剖析UPR在1型突变型CALR驱动的纤维化中的作用 (特异靶1)和2型突变体CALR驱动的ET(特异靶2)，并确定每一个是否唯一 对普遍定期审议不同部门的治疗目标敏感(具体目标3)。