Clinical Significance of Residual Myeloid Leukemia

描述（由申请人提供）：大约一半患有急性髓性白血病（AML）的儿童最终死于疾病。该研究的长期目标是通过微小残留疾病（MRD）的敏感识别和白血病干细胞的跟踪来改善这些患者的临床管理（从而改善他们的结果）。申请人实验室开发的流式细胞术方法可以从1000个或更多的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地应用于监测85%的AML儿童的MRD。缓解诱导后MRD阳性是治疗失败的最有力预测因子。本申请中提出的研究以AML的多机构研究为基础，该研究对大约200名新诊断为AML的儿童进行了骨髓和外周血的顺序MRD检查。目标1是通过识别新的白血病细胞标记物，将敏感的MRD监测（即在10,000或更多正常细胞中检测1个AML细胞）扩展到所有AML儿童。提出的策略依赖于AML细胞（已研究的150例）与正常未成熟骨髓细胞的基因表达谱的比较，以识别AML中差异表达的基因。新鉴定的标记物的MRD检测将与标准流式细胞术和分子MRD检测相比较。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亚群驱动的，这可能是AML有效治疗的最相关靶点。然而，白血病干细胞在急性髓性白血病中的临床意义尚未得到系统的解决。因此，Aim 2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试验，以确定诊断时AML干细胞的患病率，并确定其持久性对预后的影响。目的3旨在评估MRD检测应用于外周血而不是骨髓的临床效用。根据初步结果，期望MRD检测灵敏度的提高将使MRD能够在大多数（如果不是全部）骨髓MRD患者的外周血中被识别出来，从而增强对AML儿童进行更频繁的MRD监测的前景。这方面的研究将确定更高水平的血液MRD和循环白血病干细胞是否与更高的复发风险相关。

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.