Understanding the niche of minimal residual disease leukemia cells

项目摘要 当急性淋巴细胞白血病（ALL）细胞逃避细胞减灭化疗的毒性时， 残留病（MRD）和复发。监测和报告司仍然是一个主要障碍，目前的方案没有解决这一问题。 治疗最近，整合素α 6（Itga 6）被鉴定为新的流式细胞术MRD标记物。为什么选择Itga 6 标记MRD ALL细胞未知。我们开发了新的模型来研究MRD的出现。这本小说 MRD ALL模型使我们能够对MRD附近的骨髓（BM）细胞进行原位表征 ALL细胞和这种MRD ALL细胞与BM小生境的相互作用的实时体内可视化， 我们研究MRD ALL细胞与BM的实时相互作用。我们的初步数据确定Itga 6是一个细胞 层粘连蛋白在特定ALL细胞亚型上的表面粘附受体，其保护这些细胞免受药物 治疗然而，我们的数据也表明Itga 6具有独立于层粘连蛋白的促存活功能。 此外，Cre介导的Itga 6在体外小鼠前B ALL细胞中的缺失可重复地诱导细胞凋亡。在 原发性ALL异种移植物模型，用P5 G10（一种Itga 6特异性Ab）联合化疗治疗， 提高白血病小鼠的存活率。正如我们的数据显示，Itga 6和另一个 粘附分子，Itga 4，不同，这也是表达在所有细胞，不同，我们将测试一个新的概念， 双重整联蛋白抑制作为ALL的治疗策略。初步的质谱分析提供了 观察到的Itga 6相关凋亡的机制相关性，为研究 Itga 6如何促进ALL细胞存活的潜在机制。我们的总体假设和前提 这些研究表明，MRD前B ALL细胞位于BM中的特定小生境中，并且Itga 6表达 在ALL细胞中是赋予白血病起始细胞特征的关键组分，包括药物 对MRD细胞不敏感。以下目标将检验这一假设：目标1将描述BM利基 细胞与MRD ALL细胞原位接触，并在体内和体外实时接触。目标2确定了基础 Itga 6促进MRD ALL存活的机制。最后，目标3将临床前评估Itga 6的概念 单独抑制和与Itga 4抑制组合以根除MRD ALL。我们建议的研究可能 进一步建立了原理证明，其中Itga 6/BM相互作用的中断废除了对 针对ALL的MRD利基，改变当前治疗ALL的概念，包括针对MRD的策略 利基

PROJECT SUMMARY When acute lymphoblastic leukemia (ALL) cells evade the toxicity of cytoreductive chemotherapy, minimal residual disease (MRD) and relapse ensue. MRD remains a major obstacle, which is unaddressed by current therapies. Recently, integrin alpha6 (Itga6) was identified as a novel flow cytometric MRD marker. Why Itga6 marks MRD ALL cells is unknown. We developed novel models to study the emergence of MRD. This novel MRD ALL model enables us to perform in situ characterization of bone marrow (BM) cells neighboring MRD ALL cells and in vivo visualization of interactions of such MRD ALL cells with BM niches in real-time allowing us to study real-time interactions of MRD ALL cells with the BM. Our preliminary data identify Itga6 as a cell surface adhesion receptor for laminin on specific ALL cell subtypes which protects these cells against drug treatment. However, our data also show that Itga6 has a pro-survival function independent of laminin. Moreover, Cre-mediated deletion of Itga6 in murine pre-B ALL cells in vitro reproducibly induces apoptosis. In xenograft model of primary ALL, combination chemotherapy treatment with P5G10, an Itga6-specific Ab, enhanced survival of leukemia bearing mice. As our data show that the functions of Itga6 and another adhesion molecule, Itga4, differ which also is expressed on ALL cells, differ, we will test a novel concept of dual integrin inhibition as treatment strategy for ALL. Preliminary mass spectrometry analysis provides mechanistic correlates of observed Itga6-associated apoptosis which provide the basis for studying the underlying mechanism of how Itga6 promotes survival of ALL cells. Our overall hypothesis and premise for these studies is that MRD pre-B ALL cells are located in a specific niche in the BM, and that Itga6 expression in ALL cells is a critical component that imparts leukemia-initiating cell characteristics, including drug insensitivity, to MRD cells. The following aims will test this hypothesis: Aim 1 will characterize the BM niche cells in contact with MRD ALL cells in situ and in real-time in vivo and in vitro. Aim 2 determines the underlying mechanism of Itga6-promoted MRD ALL survival. Finally, Aim 3 will preclinically evaluate the concept of Itga6 inhibition alone and in combination with Itga4 inhibition to eradicate MRD ALL. Our proposed studies may further establish the proof-of-principle in which interruption of the Itga6/BM interaction abrogates protection of the MRD niche to ALL, changing current concepts of treating ALL to include strategies targeting the MRD niche.