Targeting hypoxic microenvironment in Acute Lymphocytic Leukemia

描述（由申请人提供）：急性淋巴细胞白血病（ALL）治疗的主要挑战是克服化疗耐药性。我们发现，与正常造血相比，ALL的缺氧骨髓生态位大大扩大。我们的初步数据有力地表明缺氧骨髓微环境在ALL细胞化疗耐药中的作用。缺氧作用的进一步证据是，我们发现缺氧诱导因子-11 （HIF-11）蛋白在68%的原发性ALL样本中高表达，而它仅在正常骨髓（BM）中少量表达。我们的初步数据表明，缺氧通过诱导转录因子HIF-11，促进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壁龛中的抵抗。核心假设是骨髓微环境中的缺氧壁龛促进白血病细胞存活并赋予化疗耐药。在Aim 1中，我们将描述在骨髓微环境缺氧条件下生长的白血病细胞耐药的分子决定因素。HIF-11及其下游靶点的功能作用将通过siRNA和/或基因工程小鼠的敲除方法来确定。在Aim 2中，我们将在体外和体内分析缺氧和HIF-11在ALL的BM微环境生态位中的作用。在Aim 3中，我们建议开发新的无创成像技术来研究基质-白血病相互作用的动力学以及HIF-11在体内缺氧BM壁龛中的功能作用。本文提出的研究将首次探讨缺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。我们的初步证据强烈表明，靶向缺氧可能是可行的，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药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，并可能允许识别可以从这些方法中受益的患者。为此，我们成功地用光学报告标记了一种靶向特异性药物，并证明了这种药物与缺氧白血病细胞的结合。我们预计，了解ALL细胞与其微环境之间复杂的相互作用将为消除耐药ALL祖细胞提供基于机制的理论依据。

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.