Clinical Significance of Residual Myeloid Leukemia

描述（由申请人提供）：大约一半的儿童急性髓性白血病（AML）最终死于他们的疾病。拟议研究的长期目标是通过敏感地识别微小残留病（MRD）和跟踪白血病干细胞来改善这些患者的临床管理（从而改善其结局）。申请人实验室开发的流式细胞术方法可以在1000个或更多正常造血细胞中区分1个白血病骨髓细胞，并且在初步研究中，成功应用于监测85% AML儿童的MRD。缓解诱导后阳性MRD结果是治疗失败的最有力预测因素。本申请中提出的研究基于AML的多机构研究，该研究规定了约200名新诊断AML儿童的骨髓和外周血中的连续MRD检查。目标1是扩展敏感的MRD监测（即，1 AML细胞在10，000或更多的正常细胞）的所有儿童与AML通过识别新的白血病细胞标记。所提出的策略依赖于AML细胞（已经研究了150例）的基因表达谱与正常未成熟骨髓对应物的基因表达谱的比较，以确定AML中差异表达的基因。将根据标准流式细胞术和分子MRD测定法检测新鉴定标志物的MRD检测。越来越多的证据表明，AML是由转化的造血干细胞的一个独特子集驱动的，这可能是有效AML治疗的最相关靶点。然而，白血病干细胞在AML中的临床意义尚未得到系统的解决。因此，目标2中的研究将依赖于新开发的流式细胞术方法和体外和体内白血病细胞生长测定，以确定诊断时AML干细胞的患病率，并确定其持续存在的预后影响。目的3旨在评估应用于外周血而不是骨髓的MRD测定的临床实用性。基于初步结果，预期MRD检测灵敏度的提高将允许在大多数（如果不是所有）骨髓MRD患者的外周血中识别MRD，从而增强AML儿童更频繁监测MRD的前景。这方面的研究将确定血液MRD和循环白血病干细胞水平是否与复发风险较高相关。

DESCRIPTION (provided by applicant): Approximately half of children with acute myeloid leukemia (AML) eventually succumb to their disease. The long-term objective of the proposed research is to improve the clinical management of these patients (and hence their outcome) through sensitive identification of minimal residual disease (MRD) and tracking of leukemia stem cells. A flow cytometric method developed in the applicant's laboratory can distinguish 1 leukemic myeloid cell among 1000 or more normal hematopoietic cells and, in preliminary studies, was successfully applied in monitoring MRD in 85% of children with AML. A positive MRD finding after remission induction was the most powerful predictor of treatment failure.The studies proposed in this application are grounded in a multi-institutional study of AML, which specifies sequential MRD examinations in bone marrow and peripheral blood in approximately 200 children with newly diagnosed AML. Aim 1 is to extend sensitive MRD monitoring (i.e., 1 AML cell in 10,000 or more normal cells) to all children with AML by identifying novel leukemic cell markers. The proposed strategy relies on comparison of the gene expression profiles of AML cells (150 cases already studied) with those of normal immature myeloid counterparts to identify genes differentially expressed in AML. MRD detection by the newly identified markers will be tested against standard flow cytometric and molecular MRD assays. There is mounting evidence that AML is driven by a distinct subset of transformed hematopoietic stem cells, which are likely to be the most relevant targets for effective AML therapy. However, the clinical significance of leukemia stem cells in AML has not yet been systematically addressed. Thus, studies in Aim 2 will rely on newly-developed flow cytometric methods and on leukemia cell growth assays in vitro and in vivo to establish the prevalence of AML stem cells at diagnosis and determine the prognostic impact of their persistence. Aim 3 seeks to assess the clinical utility of MRD assay applied to peripheral blood instead of bone marrow. Based on preliminary results, the expectation is that improvements in the sensitivity of MRD assays will allow MRD to be identified in the peripheral blood of most if not all patients with bone marrow MRD, enhancing the prospects for more frequent MRD monitoring in children with AML. Studies in this aim will determine whether higher levels of blood MRD and of circulating leukemic stem cells correlate with a higher risk of relapse.