Synthetic lethality in leukemic stem cells in juvenile myelomonocytic leukemia

幼年型粒单核细胞白血病干细胞的综合致死率

• 批准号: 10308711
• 负责人: CHENG-KUI QU
• 金额: $ 21.44万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-01 至 2022-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10308711
• 关键词: Adolescent; Antipsychotic Agents; Area; Biological; Blood; Cell Death; Cells; Characteristics; Childhood; Clinical; DNA Sequence Alteration; Data; Development; Disease; Drug resistance; Experimental Leukemia; Exploratory/Developmental Grant; Funding Opportunities; Growth; Growth Factor; Hematologic Neoplasms; Hematopoietic; Hematopoietic stem cells; Hyperactivity; Impairment; Investigation; Juvenile Myelomonocytic Leukemia; Knock-in; Knock-in Mouse; Knock-out; Lead; Maintenance; Malignant Neoplasms; Methodology; Modeling; Mus; Mutant Strains Mice; Mutate; Mutation; Myeloproliferative disease; NIH Program Announcements; Outcome; Pathogenesis; Pathway interactions; Patients; Penetrance; Pharmacology; Phenotype; Phosphorylation; Pimozide; Plant Roots; Population; Prognosis; Property; Protein Dephosphorylation; Protein Tyrosine Phosphatase; Proteins; Relapse; Research; Risk; Role; Signal Transduction; Signaling Protein; Source; Techniques; Testing; Therapeutic; Therapeutic Effect; Transplantation; Treatment Failure; Tyrosine; Xenograft Model; anticancer research; base; cancer diagnosis; cytokine; early childhood; inhibitor; leukemia; leukemic stem cell; mouse model; mutant; neoplastic cell; novel; novel strategies; novel therapeutic intervention; pre-clinical; precursor cell; response; self-renewal; stem cells; therapeutic development; therapeutic evaluation; therapeutically effective; transcription factor

Project Summary Juvenile myelomonocytic leukemia (JMML), a clonal hematological malignancy of early childhood, has limited therapeutic options. Relapse remains the main cause of treatment failure, most likely due to the persistence of leukemic stem cells (LSCs), a small population of self-renewing precursor cells that give rise to the bulk of tumor cells. This reservoir of tumor cells is responsible for long-term maintenance of leukemia growth and is also a major source of drug resistance. Therefore, a novel treatment approach focused on the unique characteristics and vulnerabilities of LSCs is needed in order to target this root cause of JMML. However, it remains a critical challenge how these leukemic precursor cells may be eradicated. JMML is caused by various genetic mutations in the signaling proteins involved in the Ras pathway, among which protein tyrosine phosphatase Ptpn11 (Shp2), a positive regulator of the Ras pathway, is most frequently mutated. These mutations cause greatly increased catalytic activity of Shp2, and JMML patients with Ptpn11 mutations have the worst prognosis in all subtypes of JMML. We previously created a line of conditional knock-in mice with the Ptpn11E76K mutation, the most common and active Ptpn11 mutation found in JMML. Induction of the Ptpn11E76K/+ mutation in these mice (Ptpn11E76K/+/ Mx1-Cre+) resulted in JMML-like myeloproliferative neoplasm (MPN) with full penetrance, suggesting a causative role of this mutation in the pathogenesis of JMML. In an effort to understand the biological properties of leukemic precursor cells in JMML, we recently examined mutated hematopoietic stem cells in this mouse model (referred to as LSCs) and found that Stat5 was hyper-activated. More importantly, Ptpn11E76K/+ LSCs appeared to rely on Stat5 for maintenance and self-renewal because deletion of Stat5 in Ptpn11E76K/+/Mx1-Cre+/Stat5fl/fl double mutant mice resulted in massive LSC cell death while neither Stat5 knockout nor Ptpn11E76K/+ knock-in alone mice had such phenotypes in stem cells. Consequently, the LSC pool in Ptpn11E76K/+/Mx1-Cre+/Stat5fl/fl double mutant mice was markedly decreased. Further mechanistic investigation revealed that this was because tyrosine (Tyr705) phosphorylation of Stat3, one of the Shp2 substrate proteins, was decreased by 3 to 5-fold in Ptpn11E76K/+ LSCs likely due to enhanced dephosphorylation by the hyperactive Shp2 E76K mutant. Thus, diminished Stat3 activity represents an Achilles’ heel of Ptpn11E76K/+ LSCs, making them vulnerable to Stat5 depletion-induced cell death. The synthetic lethality induced by loss of Stat5 in Ptpn11-activated JMML stem cells raises an intriguing possibility, i.e., pharmacological inhibition of Stat5 might be effective in eradicating LSCs in this subtype of JMML. We plan to test this hypothesis and accomplish the objective of this project by pursuing the following two aims. 1) To define the role of Stat5 in maintenance of LSCs in Ptpn11-associated JMML. 2) To test the therapeutic effects of the Stat5 inhibitor pimozide, a clinically used antipsychotic drug, in Ptpn11 (Shp2)-activated JMML.

项目概要 幼年型粒单核细胞白血病（JMML）是一种儿童早期的克隆性血液恶性肿瘤，其发病率有限。 治疗选择。复发仍然是治疗失败的主要原因，很可能是由于疾病的持续存在 白血病干细胞 (LSC)，一小群自我更新的前体细胞，可产生大部分肿瘤 细胞。这种肿瘤细胞库负责长期维持白血病的生长，也是一种 耐药性的主要来源。因此，一种针对独特特征的新型治疗方法 为了解决 JMML 的根本原因，需要 LSC 的漏洞。然而，它仍然是一个关键 挑战如何根除这些白血病前体细胞。 JMML是由多种基因突变引起的 参与 Ras 通路的信号蛋白，其中蛋白酪氨酸磷酸酶 Ptpn11 (Shp2)、 Ras 通路的正调节因子，最常发生突变。这些突变导致大大增加 Shp2 的催化活性，Ptpn11 突变的 JMML 患者在所有亚型中预后最差 JMML。我们之前创建了一系列带有 Ptpn11E76K 突变的条件敲入小鼠，这是最常见的突变 在 JMML 中发现了活跃的 Ptpn11 突变。在这些小鼠中诱导 Ptpn11E76K/+ 突变（Ptpn11E76K/+/ Mx1-Cre+）导致具有完全外显率的 JMML 样骨髓增生性肿瘤（MPN），表明致病因素 该突变在 JMML 发病机制中的作用。为了了解白血病的生物学特性 JMML 中的前体细胞，我们最近在该小鼠模型中检查了突变的造血干细胞（称为 作为 LSC）并发现 Stat5 被过度激活。更重要的是，Ptpn11E76K/+ LSC 似乎依赖于 Stat5 用于维持和自我更新，因为在 Ptpn11E76K/+/Mx1-Cre+/Stat5fl/fl 双突变体中删除了 Stat5 小鼠导致大量 LSC 细胞死亡，而 Stat5 敲除小鼠和 Ptpn11E76K/+ 单独敲入小鼠均未发生这种情况。 干细胞中存在这样的表型。因此，Ptpn11E76K/+/Mx1-Cre+/Stat5fl/fl 双突变小鼠中的 LSC 库 明显减少。进一步的机制研究表明，这是因为酪氨酸（Tyr705） Shp2 底物蛋白之一 Stat3 的磷酸化在 Ptpn11E76K/+ LSC 中降低了 3 至 5 倍 可能是由于高度活跃的 Shp2 E76K 突变体的去磷酸化增强所致。因此，Stat3 活性减弱 代表 Ptpn11E76K/+ LSC 的致命弱点，使它们容易受到 Stat5 耗尽引起的细胞死亡的影响。 Ptpn11 激活的 JMML 干细胞中 Stat5 缺失引起的合成致死率引起了有趣的研究 的可能性，即 Stat5 的药理学抑制可能有效根除这种 JMML 亚型中的 LSC。 我们计划通过追求以下两个目标来检验这一假设并实现该项目的目标。 1） 定义 Stat5 在 Ptpn11 相关 JMML 中 LSC 维护中的作用。 2）测试治疗效果 Stat5 抑制剂匹莫齐特（一种临床使用的抗精神病药物）在 Ptpn11 (Shp2) 激活的 JMML 中的作用。