Eltombopag: Novel Mode of Action on Normal and Aplastic Anemia Hematopoietic Stem Cells

Eltombopag：对正常和再生障碍性贫血造血干细胞的新作用模式

• 批准号: 10676888
• 负责人: Babal K Jha
• 金额: $ 65.88万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2027-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10676888
• 关键词: Affect; Aftercare; Agonist; Aplastic Anemia; Ascorbic Acid; Binding; Biochemical; Biological; Biological Models; Blood Cells; Bone marrow failure; CD34 gene; Catalytic Domain; Cell Line; Cell Lineage; Cells; Chemicals; Clinical; Clinical Data; Clinical Research; Coupled; Cryoelectron Microscopy; Crystallography; DNA; DNA methylation profiling; Dependence; Dioxygenases; Elderly; Engraftment; Enhancers; Enzymes; Epigenetic Process; Failure; Gene Expression Profile; Gene Mutation; Genes; Hematology; Hematopoiesis; Hematopoietic; Hematopoietic stem cells; Human; Hypermethylation; Immune; Immune mediated destruction; In Vitro; In complete remission; Individual; Iron; Iron Chelating Agents; Iron Chelation; Kinetics; MPL gene; Mediating; Modeling; Molecular; Mus; Myelogenous; Neoplasms; Pathway interactions; Patients; Peptides; Pharmaceutical Preparations; Platelet Count measurement; Population; Production; Proliferating; Property; Proteins; RNA; Radiation; Recovery; Refractory; Relapse; Residual state; Resolution; Role; Signal Transduction; Somatic Mutation; System; Testing; Therapeutic; Therapeutic immunosuppression; Thrombocytopenic Purpura; alpha ketoglutarate; analog; base; bone marrow failure syndrome; clinically relevant; cofactor; demethylation; design; epigenetic regulation; extracellular; hematopoietic stem cell expansion; high throughput screening; improved; in vivo; in vivo Model; inhibitor; leukemia; loss of function mutation; mRNA Expression; mimetics; mouse model; novel; polypeptide; promoter; receptor-mediated signaling; response; small molecule; stem cells; success; transcriptome sequencing

Summary Idiopathic aplastic anemia (AA) is characterized by immune-mediated hematopoietic stem and progenitor cells (HSPCs) destruction resulting in deficiencies across all hematopoietic lineages and bone marrow failure. Despite of the therapeutic successes of immunosuppressive therapies (IST), approximately one third of patients remain refractory and many of the responses are incomplete. Recently, a synthetic thrombopoietin receptor (TPOR) agonist, Epag has been shown to be effective in AA. In addition to the anticipated effect on platelet counts, Epag also produced remarkable tri-lineage hematopoiesis. These effects expanded the indication spectrum of Epag from immune thrombocytopenic purpura to AA, establishing this drug as an essential hematologic therapeutic. Recent studies demonstrate that Epag’s hematopoietic activity is also observed in murine models despite the lack of binding to murine TpoR. We confirmed similar effects in murine cells where Epag treatment remarkably expanded HSCs without any effect on the TpoR signaling. These observations suggested that a significant part of Epag’s activities are TPOR independent, in contrast to peptide TPO analogs, e.g., romiplostin. These TPOR independent effects of Epag were hypothesized to be due to its iron chelating properties, but the molecular mechanism as to how this iron-binding could drive the HSPCs expansion remains speculative. Epag effects on intracellular iron may affect certain iron-dependent epigenetic pathway/s that promote HSPCs self-replication. For instance, TET-dioxygenases (TET1-3) are Fe2+- and α- ketoglutarate (αKG) dependent DNA-dioxygenases, which mediate CpG demethylation of promoters and enhancers in HSPCs. Consequently, by changing gene expression patterns, TETs control HSPCs expansion and differentiation. TET2 is the most abundant TET-dioxygenase in HSPCs, and somatic loss-of-function (LOF) mutations of this gene frequently occur in myeloid neoplasia and clonal hematopoiesis of indeterminate potential (CHIP), a prodromal condition in otherwise healthy elderly individuals characterized by high progression rate to a frank leukemia. Our proposal is designed to determine the effects of Epag on normal hematopoiesis mediated by its ability to inhibit TET-activity. Based on our analysis of clinical data coupled with biochemical analysis we hypothesize that, Epag-mediated TET- inhibition is responsible for tri-lineage response in AA via HSC expansion and on the biochemical level decreased 5hmC content leading to hypermethylation as a result of direct inhibition of TET2. Our current proposal will provide a proof of concept for the reversible transient TET-inhibition as a basis for HSC expansion that may restore normal hematopoiesis.

摘要 特发性再生障碍性贫血(AA)的特征是免疫介导的造血干细胞和 祖细胞(HSPC)的破坏导致所有造血系的缺陷 和骨髓衰竭。尽管免疫抑制疗法的治疗取得了成功 (IST)，大约三分之一的患者仍然难以治愈，许多反应是 不完整。最近，一种合成的血小板生成素受体(TpoR)激动剂EPAG被发现 在再生障碍性贫血中发挥作用。除了对血小板计数的预期影响外，EPAG还产生了 显着的三系造血。这些效应扩展了EPAG的指示光谱 从免疫性血小板减少性紫癜到再障，确立该药为血液学必备药物 有治疗作用。最近的研究表明，EPAG的造血活性也在 小鼠模型，尽管缺乏与小鼠TpoR的结合。我们在小鼠身上证实了类似的效应 EPAG处理的细胞显著扩增HSC，但对TpoR信号转导无任何影响。 这些观察表明，EPAG的很大一部分活动是独立于TpoR的， 而不是多肽TPO类似物，例如罗米普罗汀。EPAG的这些TpoR独立效应 推测是由于其铁的螯合特性，但其分子机制 这种铁约束将如何推动HSPC的扩张仍是一种猜测。EPAG对 细胞内铁可能影响某些铁依赖的表观遗传途径/S HSPC自我复制。例如，Tet-双加氧酶(TET1-3)是Fe2+-和α-。 依赖于酮戊二酸(αKG)的双加氧酶，介导CpG去甲基化 在HSPC中的启动子和增强子。因此，通过改变基因表达 模式，Tets控制HSPC的扩张和分化。TET2是最丰富的 HSPC中的Tet-双加氧酶及其基因的体细胞功能丧失突变 多发于髓系肿瘤和克隆性造血潜能不明 (CHIP)，在其他健康的老年人中的一种前驱症状，其特征是 直白白血病的高进展率。我们的提案旨在确定 EPAG抑制Tet活性对正常造血的影响 根据我们对临床数据的分析和生化分析，我们假设， EPAG介导的Tet抑制与再生障碍性贫血的三系反应有关 在生化水平上，5hmC含量降低，导致甲基化 直接抑制TET2。我们目前的提案将为可逆的 短暂的Tet抑制作为HSC扩增的基础，可能会恢复正常的造血。