Targeting hypoxic microenvironment in Acute Lymphocytic Leukemia

描述(申请人提供)：急性淋巴细胞白血病(ALL)治疗的主要挑战是克服对化疗的耐药性。我们发现，与正常造血相比，ALL中缺氧的骨髓生态位大大扩大。我们的初步数据有力地表明了低氧骨髓微环境在所有细胞的化疗耐药中所起的作用。低氧作用的进一步证据是我们发现低氧诱导因子-11(HIF-11)蛋白在68%的原发ALL样本中高表达，而在正常骨髓(BM)中仅少量表达。我们的初步数据表明，低氧通过诱导转录因子HIF-11，促进向糖酵解代谢的转换，并上调趋化因子，每一种都有助于白血病细胞在BM利基中的耐药性。中心假说是骨髓微环境中的低氧生态位促进白血病细胞存活并产生化疗耐药。在目标1中，我们将表征在骨髓微环境低氧条件下生长的白血病原始细胞化疗耐药性的分子决定因素。HIF-11及其下游靶标的功能作用将通过利用siRNA和/或基因工程小鼠的敲除方法来确定。在目标2中，我们将剖析缺氧和HIF-11在体外和体内ALL骨髓微环境生态位中的作用。在目标3中，我们建议开发新的非侵入性成像来研究基质-白血病相互作用的动力学以及HIF-11在体内低氧骨髓微环境中的功能作用。这里提出的研究将首次探讨低氧作为白血病微环境的重要组成部分，并确定化疗耐药的下游介质。我们的初步证据有力地表明，靶向低氧可能是可行的，并可能使白血病细胞对药物敏感。由于HIF-11抑制剂和缺氧激活的前体药物都处于临床开发的早期阶段，这些研究将为未来这些药物在白血病中的临床试验提供基础。此外，在体内白血病模型中验证的成像技术将适用于人体试验，并可能允许识别可能从这些方法中受益的患者。为此，我们已经成功地用光学报告符标记靶向特异性试剂，并证明了该试剂与低氧白血病细胞的结合。我们预计，了解所有细胞与其微环境之间的复杂相互作用将为消除所有耐药的祖细胞提供基于机制的理论基础。 公共卫生相关性：这里提出的叙述性研究将首次调查低氧作为白血病微环境的重要组成部分，并确定化疗耐药的下游介质。我们的初步证据有力地表明，靶向低氧可能是可行的，并可能使白血病细胞对药物敏感。我们预计，了解所有细胞与其微环境之间的复杂相互作用将为消除耐药的所有祖细胞提供基于机制的理论基础，并为未来HIF-11抑制剂和低氧激活的前体药物的临床试验奠定基础。

DESCRIPTION (provided by applicant): The main challenge in the therapy of Acute Lymphocytic Leukemia (ALL) is overcoming resistance to chemotherapy. We have found that the hypoxic bone marrow niche in ALL is greatly expanded compared to normal hematopoiesis. Our preliminary data strongly indicate role for the hypoxic bone marrow microenvironment in chemoresistance of ALL cells. Further evidence for the role of hypoxia is our finding that the Hypoxia-Inducible Factor-11 (HIF-11) protein is highly expressed in 68% of primary ALL samples, while it is only sparingly expressed in normal bone marrow (BM). Our preliminary data indicate that hypoxia, via induction of the transcription factor HIF-11, promotes the switch to glycolytic metabolism and upregulates chemokines, each contributing to the resistance of leukemic cells in BM niches. The central hypothesis is that hypoxic niches within the BM microenvironment promote leukemia cell survival and confer chemoresistance. In Aim 1, we will characterize molecular determinants of chemoresistance of leukemic blasts grown under hypoxic conditions of the BM microenvironment. The functional role of HIF-11 and its downstream targets will be determined through utilization of knock-down approaches with siRNA and/or genetically engineered mice. In Aim 2, we will dissect the role of hypoxia and HIF-11 in the BM microenvironment niches of ALL, both in vitro and in vivo. In Aim 3, we propose to develop novel noninvasive imaging to study the dynamics of stroma-leukemia interactions and the functional role of HIF-11 in the hypoxic BM niches in vivo. Studies proposed here will for the first time investigate hypoxia as an essential component of the leukemic microenvironment and determine downstream mediators of chemoresistance. Our preliminary evidence strongly suggests that targeting hypoxia may be feasible and may render leukemic cells drug sensitive. Since both, HIF-11 inhibitors and hypoxia-activated pro-drugs are in early stages of clinical development; these studies will provide the foundation for future clinical trials with these agents in leukemia. Further, imaging techniques validated in the in vivo leukemia models will be applicable in the human trials and may allow to identify patients that could benefit from these approaches. To this end, we have successfully labeled a target- specific agent with an optical reporter and demonstrated binding of this agent to the hypoxic leukemia cells. We anticipate that understanding of the complex interactions between ALL cells and their microenvironment will provide mechanism-based rationale for eliminating resistant ALL progenitor cells. PUBLIC HEALTH RELEVANCE: Narrative Studies proposed here will for the first time investigate hypoxia as an essential component of the leukemic microenvironment and determine downstream mediators of chemoresistance. Our preliminary evidence strongly suggests that targeting hypoxia may be feasible and may render leukemic cells drug sensitive. We anticipate that understanding of the complex interactions between ALL cells and their microenvironment will provide mechanism-based rationale for eliminating resistant ALL progenitor cells and provide the foundation for future clinical trials with HIF-11 inhibitors and hypoxia-activated pro-drugs.