Targeting dormant leukemia-initiating cells in T-cell acute lymphoblastic leukemia

项目总结/摘要 治疗耐药性是儿童T细胞急性淋巴细胞白血病（T-ALL）长期缓解的主要障碍。 所有）。复发性或难治性疾病的儿童预后很差。白血病起始细胞（L-IC） 在移植到小鼠体内后再生疾病。它们还概括了免疫表型的复杂性， 母细胞白血病支持，在正常的造血中，白血病细胞之间存在细胞等级 细胞我们的实验室以前已经证明，L-IC是一种定型的胸腺细胞祖细胞， 然而，在白血病DN 3群体中，只有一部分DN 3细胞可以引起疾病。L-IC依赖于 NOTCH 1诱导的MYC信号传导用于存活。最近的研究发现，休眠，治疗抵抗L-IC在这两个 鼠模型和T-ALL患者样品。细胞周期限制在L-IC潜伏期中的作用是不完全的 明白为了揭示控制L-IC功能的途径，我们进行了单细胞RNA- 使用我们的转基因Tal 1/Lmo 2模型在T细胞白血病发生的不同阶段对胸腺细胞进行测序。 这种方法鉴定了一个休眠的DN 3簇，以低Ki 67表达为标志，这在其他细胞中观察到。 鼠T-ALL样品。Doradin DN 3细胞表现出高Notch 1，但低Myc表达。转录 这些细胞的特征显示了先前与白血病起始或白血病干细胞有关的基因的富集 细胞功能Dorothy DN 3细胞显示非典型Wnt受体Ryk的富集，据报道， 通过限制增殖和促进静止来维持造血干细胞的自我更新。RYK是 与健康胸腺相比，在原发性儿科T-ALL和Tal 1/Lmo 2诱导的小鼠T-ALL中过表达。 这表明RYK可能不限于这种罕见的亚群，此外，可能存在一种 复发性T-ALL中RYK抑制的治疗窗口。这一提议的核心假设是， DN 3细胞是保持增殖和分化能力的静止L-IC，这允许它们的治疗 耐受性和随后复发期间的扩张。这项提案将确定一个基因签名休眠DN 3 细胞，并通过评估其L-IC功能揭示这些细胞在T-ALL复发中的潜在作用， 化学抗性（Aim 1）。目标2将定义T-ALL中的非规范WNT/RYK信令网络， 这些途径在休眠的DN 3细胞和L-IC功能中的作用，通过测试RYK的抑制是否降低 小鼠和患者T-ALL细胞的L-IC频率。总的来说，这些研究将为T- ALL的异质性，并将为L-IC靶向治疗复发性疾病的发展奠定基础。

PROJECT SUMMARY/ABSTRACT Therapy resistance is a major barrier to long term remission in pediatric T-cell acute lymphoblastic leukemia (T- ALL). The prognosis for children with relapsed or refractory disease is dismal. Leukemia-initiating cells (L-ICs) regenerate disease upon transplantation into mice. They also recapitulate the immunophenotypic complexity of the parent leukemia supporting that, as in normal hematopoiesis, there is a cellular hierarchy among leukemic cells. Our laboratory has previously demonstrated that the L-IC is a committed thymocyte progenitor and resides in the leukemic DN3 population, however, only a fraction of DN3 cells can give rise to disease. L-ICs rely on NOTCH1-induced MYC signaling for survival. Recent studies identified dormant, therapy resistant L-ICs in both murine models and T-ALL patient samples. The role of cell cycle restriction in L-IC latency is incompletely understood. In an effort to uncover pathways that govern L-IC function, we performed single cell RNA- sequencing on thymocytes at varying stages of T-cell leukemogenesis using our transgenic Tal1/Lmo2 model. This approach identified a dormant DN3 cluster, marked by low Ki67 expression, which is observed in other murine T-ALL samples. Dormant DN3 cells exhibit high Notch1, but low Myc expression. The transcriptional signature of these cells shows enrichment of genes previously implicated in leukemia initiation or leukemia stem cell function. Dormant DN3 cells show enrichment of the non-canonical Wnt receptor Ryk, which is reported to maintain hematopoietic stem cell self-renewal by limiting proliferation and promoting quiescence. RYK is overexpressed in primary pediatric T-ALL and in Tal1/Lmo2-induced murine T-ALL compared to healthy thymus. This indicates that RYK may not be restricted to this rare subpopulation and moreover, there may be a therapeutic window for RYK inhibition in relapsed T-ALL. The central hypothesis of this proposal is that dormant DN3 cells are quiescent L-ICs that retain proliferative and differentiative capacity, which permits their therapy tolerance and subsequent expansion during relapse. This proposal will identify a gene signature of dormant DN3 cells and uncover the potential role of these cells in T-ALL relapse by evaluating their L-IC function and chemoresistance (Aim 1). Aim 2 will define the non-canonical WNT/RYK signaling network in T-ALL and uncover the role of these pathways in dormant DN3 cells and L-IC function by testing whether inhibition of RYK reduces the L-IC frequency of murine and patient T-ALL cells. Collectively, these studies will provide critical insight to T- ALL heterogeneity and will lay the foundation for development of L-IC targeted therapy for relapsed disease.