The Role of the Stem Cell Niche in ALL

描述（由申请人提供）：肿瘤干细胞对癌症进展和复发的贡献被认为是实体和血液系统恶性肿瘤的重大临床挑战。了解肿瘤干细胞存活和自我更新机制的关键是研究它们茁壮成长的微环境对它们的支持。造血恶性肿瘤和随后的白血病干细胞（LSC）所特有的是对骨髓微环境对细胞命运调节的贡献的既定认识。在当前的研究中，我们研究了LSC与骨髓基质细胞（BMSC）的相互作用以及BMSC维持LSC表型的机制。我们利用独特的Bcr种群；Abl+ (Ph+)所有SUP-B15细胞，共同表达一组干细胞标记物、ve -钙粘蛋白和与b谱系相关的蛋白质。在与BMSC长期共培养（LTCC）后，SUP-B15肿瘤细胞表现出三系造血功能，形成解剖上独特的三维耐药血液球，干细胞标志物Oct-4的表达增加，并具有持续高水平的缺氧诱导因子2a （HIF-2a）。SUP-B15细胞也在NOD/SCID小鼠中重建白血病，并在体内表现出分化。ve -钙粘蛋白的不稳定增加了化疗诱导的LSCs凋亡，表明它在这种新环境中发挥了重要作用。这些研究通过纳入原代、人源性、去鉴定的pro/pre-B ALL细胞进行补充，这些细胞与我们研究中使用的Ph+ SUP-B15细胞系一致，表达高水平的VE- cadherin、Oct-4和HIF-2a。通过su - b15肿瘤细胞和患者来源样本的骨髓基质LTCC模型，我们将验证骨髓微环境对VE-cadherin和Oct-4表达和稳定性的调节支持ALL中LSC表型的工作假设。我们的假设将通过完成以下具体目标来验证：(1)确定VE-cadherin对LSC表型的贡献以及VE-cadherin在LSC中被调节的机制；(2)确定基质细胞调节肿瘤细胞Oct-4表达和活性的机制；(3)建立小鼠模型，以确定具有LSC表型的Ph+细胞亚群引发白血病的关键因素。我们的长期目标是确定对白血病干细胞的骨髓生态位支持至关重要的途径，这些途径可以通过靶向肿瘤本身或生态位进行破坏。因此，现有的治疗方法可能在靶向侵袭性Ph+白血病的干细胞成分方面具有增强的功效。

DESCRIPTION (provided by applicant): The contribution of tumor stem cells to progression and relapse of cancer is recognized as a significant clinical challenge in both solid and hematologic malignancies. Critical to understanding the mechanisms of tumor stem cell survival and self-renewal is investigation of their support by the microenvironments in which they thrive. Somewhat unique to hematopoietic malignancies, and subsequently leukemic stem cells (LSC), is an established appreciation of the contribution of the bone marrow microenvironment to regulation of cell fate. In the current study we investigate the interaction of LSC with bone marrow stromal cells (BMSC) and the mechanisms by which BMSC contribute to maintenance of the LSC phenotype. We utilize a unique population of Bcr;Abl+ (Ph+) ALL SUP-B15 cells that co-express a panel of stem cell markers, VE-cadherin, and proteins associated with commitment to the B-lineage. Following long-term co- culture (LTCC) with BMSC, SUP-B15 tumor cells demonstrate tri-lineage hematopoiesis, formed anatomically distinct three dimensional chemo-resistant hemospheres, had increased expression of the stem cell marker Oct-4, and had sustained, high levels of hypoxia inducible factor-2a (HIF-2a). SUP-B15 cells also reconstituted leukemia in NOD/SCID mice, as well as demonstrating differentiation in vivo. Destabilization of VE-cadherin increased chemotherapy-induced apoptosis of LSCs suggesting an important role for it in this novel setting. These studies are supplemented by inclusion of primary, human derived, de-identified pro/pre-B ALL cells that, consistent with the Ph+ SUP-B15 cell line utilized in our studies, express high levels of VE- cadherin, Oct-4 and HIF-2a. Using a model of LTCC of bone marrow stroma with SUP-B15 tumor cells and patient-derived samples we will test the working hypothesis that a LSC phenotype in ALL is supported by bone marrow microenvironment regulation of VE-cadherin and Oct-4 expression and stability. Our hypothesis will be tested by completion of the following specific aims: (1) To determine the contribution of VE-cadherin to LSC phenotype and the mechanism by which VE-cadherin is modulated in LSC, (2) To determine the mechanisms by which stromal cells regulate expression and activity of tumor cell Oct-4, and (3) To develop a murine model to identify the critical factors involved in initiating leukemia from sub-populations of Ph+ cells with a LSC phenotype. Our long-term goal is to identify pathways that are essential to bone marrow niche support of leukemic stem cells that are amenable to disruption, either through targeting the tumor itself, or the niche. Consequently, existing therapies may have enhanced efficacy in targeting the stem cell component of aggressive Ph+ leukemia.