Overcoming Leukemia Chemoresistance in the Central Nervous System

摘要 中枢神经系统(CNS)复发是急性髓细胞白血病患者治疗失败的主要原因 淋巴细胞白血病(ALL)。值得注意的是，孤立性中枢神经系统复发发生在约3-8%的ALL和ALL儿童中 在一些临床试验中，占最初复发的30%-40%。此外，目前针对中枢神经系统的治疗是 与显著的毒性有关。因此，迫切需要新的中枢神经系统定向白血病治疗方法。 改善长期结果，同时减少与治疗相关的发病率。尽管广泛的研究已经 展示了骨髓微环境在白血病生物学中的关键作用，对中枢神经系统的影响 微环境对白血病细胞存活和化疗耐药性的影响在很大程度上是未知的。我们写了一本小说 体外共培养系统和体内异种移植方法研究中枢神经系统的作用 白血病生物学和化疗耐药性的利基。然后，我们使用这些模型系统来确定1) 在体外和体内培养的白血病细胞在脑脊液(CSF)中的存活率与 血清或介质，2)白血病细胞主要定位于中枢神经系统内的脑膜，3)白血病 与脑膜细胞共培养的细胞，或与小鼠脑膜相关的细胞，显示出更高的存活率和 化疗耐药。我们随后发现，脑膜-白血病的直接相互作用促进了白血病细胞的存活。 通过调节细胞凋亡平衡、细胞周期进程和静止。重要的是，白血病 化疗耐药是可逆的，可以通过将白血病细胞从脑膜中分离出来来克服。然后我们 使用共培养黏附试验来确定干扰白血病和 脑膜细胞。除了确定几种抑制规范细胞黏附靶点的药物外， 途径，包括CXCR4拮抗剂AMD3100，我们发现了一种新的小分子Me6TREN 造血干细胞(HSC)动员化合物，也破坏白血病和 脑膜细胞。这项研究表明，脑膜对白血病有独特而关键的影响。 化疗耐药并定义了中枢神经系统复发的新机制，超出了血液的已知作用- 大脑屏障。基于这项工作，我们的中心假设是白血病-脑膜细胞的相互作用是一种 中枢神经系统白血病细胞存活和化疗耐药的关键调节因子。此外，从一个治疗性的 我们假设，在中枢神经系统中，生态位破坏可能比在骨髓中更有效 这是因为相对于血液或血清，脑脊液的支持环境较差。这个项目的目标是 建议使用我们的中枢神经系统白血病的体外和体内模型系统来解剖分子 在中枢神经系统中介导白血病黏附(Aim 1)和化疗耐药(Aim 2)的机制和测试新， 治疗中枢神经系统白血病的临床可转化疗法包括Me6TREN和AMD3100(目标3)。 好了！

ABSTRACT Central nervous system (CNS) relapse is a major cause of treatment failure among patients with acute lymphoblastic leukemia (ALL). Notably, isolated CNS relapse occurs in ~3-8% of children with ALL and accounts for 30–40% of initial relapses in some clinical trials. Furthermore, current CNS-directed therapies are associated with significant toxicities. As a result, novel CNS-directed leukemia therapies are urgently needed to improve long-term outcomes while decreasing treatment-related morbidity. Although extensive research has demonstrated a critical role of the bone marrow microenvironment in leukemia biology, the impact of the CNS microenvironment on leukemia cell survival and chemoresistance is largely unknown. We developed a novel ex vivo co-culture system and an in vivo xenotransplantation approach to investigate the effects of the CNS niche on leukemia biology and chemoresistance. We then used these model systems to identify that 1) leukemia cells cultured in cerebral spinal fluid (CSF) in vitro and in vivo have diminished survival relative to serum or media, 2) leukemia cells predominantly localize to the meninges within the CNS, and 3) leukemia cells co-cultured with meningeal cells, or associated with the meninges of mice, exhibit enhanced survival and chemoresistance. We then identified that direct meningeal-leukemia interactions promote leukemia cell survival by modulating apoptosis balance, cell cycle progression, and quiescence. Importantly, leukemia chemoresistance was reversible and overcome by detaching the leukemia cells from the meninges. We then used a co-culture adhesion assay to identify drugs that disrupt the interaction between leukemia and meningeal cells. In addition to identifying several drugs that inhibit canonical cell adhesion targets and pathways, including the CXCR4 antagonist AMD3100, we found that Me6TREN, a novel small-molecule hematopoietic stem cell (HSC) mobilizing compound, also disrupts the interaction between leukemia and meningeal cells. This work demonstrates that the meninges exert a unique and critical influence on leukemia chemoresistance and defines novel mechanisms of CNS relapse beyond the well-described role of the blood- brain barrier. Based on this work, our central hypothesis is that the leukemia-meningeal cell interaction is a critical regulator of leukemia cell survival and chemoresistance in the CNS. Moreover, from a therapeutic standpoint, we hypothesize that niche disruption may be more efficacious in the CNS than in the bone marrow because of the less supportive environment of the CSF relative to the blood or serum. The objectives in this proposal are to use our in vitro and in vivo model systems for CNS leukemia to dissect the molecular mechanisms that mediate leukemia adhesion (Aim 1) and chemoresistance (Aim 2) in the CNS and test novel, clinically translatable therapies for CNS leukemia including Me6TREN and AMD3100 (Aim 3). !