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;其特征在于过度的骨髓增生。 骨髓基质中巨核细胞和粒细胞的增殖以及异常胶原沉积）， 原发性血小板增多症（ET;增加的巨核细胞和血小板生成）和真性红细胞增多症（PV; 增加红细胞生成、血红蛋白和血细胞比容）。虽然所有的MPN驱动突变导致 JAK/STAT信号传导的组成性激活，靶向JAK抑制剂不是治愈性的，不能改变疾病 进展因此，对于鉴定用于MPN的新型治愈性疗法存在巨大的未满足的需求。突变 钙网蛋白（CALR）是MPN中第二常见的遗传异常。CALR基因编码 一种主要存在于内质网（ER）中的钙（Ca 2+）结合伴侣蛋白。所有CALR 突变共享一个相同的新变体C-末端肽，其允许与血小板生成素结合 受体MPL和随后的致病性JAK/STAT信号传导的激活。大多数CALR突变 基于与野生型蛋白质的同源性程度被分类为1型或2型，其中1型 蛋白质表现出保留在2型中的C-末端Ca 2+结合位点的完全丧失。尽管他们分享 突变的C-末端和结合并激活MPL的能力，1型和2型CALR突变产生显著的 表型和预后差异。1型突变在PMF中更常见，并且与 ET导致骨髓纤维化转化的风险增加。相反，2型突变主要与 在ET中，表现出低的骨髓纤维化转化发生率，并且很少在PMF中发现。的机制 这些不同临床表型的基础仍然未知。我们发现IRE 1a/XBP 1通路 未折叠蛋白应答（UPR）在1型与2型突变CALR细胞中被差异激活， 1型突变CALR细胞依赖于这一途径生存并驱动ET。我们发现 IRE 1a/XBP 1仅被1型而非2型突变CALR激活，这是由于钙结合功能丧失 1型蛋白质的特异性。最近，我们发现UPR的ATF 6通路差异性上调- 与1型突变CALR细胞相比，2型突变蛋白在2型中受到调控，并且2型突变蛋白表现出缺乏表达。 分子伴侣功能这些数据支持中心假设，即1型和2型CALR 突变基于其各自的功能丧失激活并依赖于UPR的不同臂，以及 这些途径促进不同的疾病表型。因此，针对普遍定期审议的不同分支， 突变型可能代表了1型与2型CALR+ MPN的新型个体化治疗策略 患者为了验证这一假设，我们将剖析UPR在1型突变CALR驱动的纤维化中的作用， （特异性目标1）和2型突变CALR驱动的ET（特异性目标2），并确定每个是否是唯一的 对UPR的不同臂的治疗靶向敏感（具体目标3）。