Molecular Characterization of Acute Myeloid Leukemia

描述（由申请人提供）：本次竞争性更新建议继续我们的努力，以描述急性髓性白血病（AML）的研究，这些研究建立在我们在当前资助期内在小鼠模型和人类白血病中取得的重大发现的基础上。在1998年，我们发现小鼠AML是一个多阶段的过程，涉及抵抗程序性细胞死亡的细胞的克隆扩增。在2000年，我们发现，只有多能祖细胞（MPP）阶段的细胞在人类AML与AML 1-ETO易位是白血病细胞;更重要的是，在相同的患者，易位是存在于正常的自我更新的造血干细胞（HSC）。我们提出，白血病前阶段的发展只能发生在自我更新克隆的HSC，和一些克隆的进展白血病干细胞（LSC）的MPP阶段。这些LSC是唯一真正负责驱动疾病的细胞。MPP，而不是前体HSC或后代母细胞，将白血病转移到免疫缺陷小鼠。最近的证据表明，癌症干细胞（CSC）对靶向其后代增殖细胞的化疗和放疗更具抵抗力。因此，肿瘤通常响应于化疗而缩小，但由于癌症干细胞的抗性，几乎普遍复发。癌症干细胞模型的一个关键含义和要求是，只有杀死LSC/CSC的疗法才能治愈患者。因此，为了开发CSC靶向治疗，有必要鉴定LSC特异性分子和对其发病机制至关重要的失调分子和途径。我们在这里提出了3个目的，旨在增加我们对人类AML LSC的理解，以便在治疗上靶向它们。首先，根据新的报告和我们自己的发现，我们将从新发AML患者样本中对LSC进行严格的鉴定和定量，并研究这些LSC的正常对应物。其次，我们将研究CD 96在人类AML的进展和发病机制中的功能作用，并研究靶向CD 96作为治疗策略的潜在方法。在当前资助期内，两项独立研究将CD 96确定为候选的LSC特异性标志物。最后，我们将通过检查巨噬细胞和树突状细胞的各种亚群吞噬白血病细胞并将抗原呈递给适应性免疫系统的能力，来检查白血病细胞上的CD 47表达（“不要吃我”信号）是否使它们对先天性（巨噬细胞）和适应性（肿瘤抗原的树突状细胞呈递）免疫系统不可见。我们将测试阻断性抗CD 47抗体是否可以克服这种影响，并使它们对免疫清除敏感。

DESCRIPTION (provided by applicant): This competitive renewal proposes to continue our efforts characterizing acute myelogenous leukemia (AML) with studies that build on the significant findings that we achieved in the current funding period in both mouse models and human leukemia. In 1998 we showed that mouse AML was a multistage process involving clonal expansion of cells that resist programmed cell death. In 2000 we found that only multipotent progenitor (MPP) stage cells in human AML with AML1-ETO translocations are leukemia cells; more importantly, in the same patients, the translocation is present in normal self-renewing blood stem cells (HSC). We proposed that pre-leukemic stages of development can only occur in self-renewing clones of HSC, and that some clones progress to leukemia stem cells (LSC) at the stage of MPP. These LSC are the only cells truly responsible for driving the disease. The MPP, but not precursor HSC or progeny blast cells, transfer the leukemia to immunodeficient mice. Recent evidence has revealed cancer stem cells (CSC) to be more resistant to chemo- and radiotherapy that target their progeny proliferating cells. Thus, tumors often shrink in response to chemotherapy, but almost universally recur due to resistance of the cancer stem cells. A key implication and requirement of the cancer stem cell model is that only therapies that kill LSC/CSC can cure the patient. Thus, in order to develop CSC-targeted therapies, it is necessary to identify molecules specific to the LSC and dysregulated molecules and pathways that are critical for their pathogenesis. We propose here 3 aims designed to increase our understanding of human AML LSC in order to therapeutically target them. First, in light of new reports and our own findings, we will conduct a rigorous identification and quantification of LSC from patient samples of de novo AML, as well as investigate the normal counterparts to these LSC. Second, we will investigate the functional role of CD96 in the progression and pathogenesis of human AML, and investigate potential methods of targeting CD96 as a therapeutic strategy. During the current funding period, CD96 was identified as a candidate LSC-specific marker in two independent studies. Finally, we will examine whether CD47 expression (a 'don't eat me' signal) on leukemic cells renders them invisible to the innate (macrophage) and adaptive (dendritic cell presentation of tumor antigens) immune systems by examining the ability of various subsets of macrophages and dendritic cells to phagocytose leukemic cells and present antigen to the adaptive immune system. We will test whether a blocking anti-CD47 antibody can overcome this effect and render them susceptible to immune clearance.