Arsenic Trioxide activated pathways in malignant cells

描述（由申请人提供）：这是一项竞争性更新申请，其总体目标是确定三氧化二砷（As2O3）抗白血病作用的产生机制，并开发增强其抗肿瘤特性的手段和方法。As2O3是一种重金属衍生物，在体外和体内均具有较强的抗白血病活性，对急性早幼粒细胞白血病（APL）患者的治疗非常有效。尽管在该领域取得了进展，并且对将砷应用于其他血液系统恶性肿瘤有很高的兴趣，但As2O3诱导抗白血病反应的确切机制尚不清楚。我们提供了第一个证据，证明As2O3诱导的自噬对髓系白血病患者原始白血病祖细胞的抑制作用至关重要。目前的建议是一种系统的方法来定义导致As2O3依赖性自噬的细胞事件，并确定自噬介导的原始白血病前体和白血病起始干细胞（lic）中致癌蛋白降解的机制。具体目的1将研究白血病祖细胞中As2O3 -自噬的机制。将进行研究以确定白血病细胞自噬级联中的上游激酶，并确定导致其在砷反应中激活的事件序列。其他研究将研究自噬与As2O3诱导的细胞负反馈调节通路（NFRPs）的关系。特异性目标2将确定自噬介导砷对AML和CML患者原始祖细胞和白血病起始干细胞反应的效应机制。将进行实验来确定自噬是否介导不同癌蛋白的砷依赖性降解，并确定这种降解发生的精确机制。其他研究将确定自噬机制元件的药理学或分子靶向是否可以增强砷诱导的原始白血病前体和lic的抑制。特异性目的3将研究自噬在体内不同白血病小鼠模型中砷依赖性抗白血病反应中的作用。它包括实验来确定As2O3的抗白血病特性是否需要自噬，并检查自噬的其他诱导剂是否与As2O3表现出协同抗白血病活性。总之，这项工作将促进我们对As2O3产生抗白血病反应的机制的理解。它应该具有重要的临床转化意义，并可能导致开发新的方法来靶向早期祖细胞和lccs，使用As2O3与其他自噬诱导剂的组合。

DESCRIPTION (provided by applicant): This is a competing renewal application whose overall objective is to define the mechanisms of generation of the antileukemic effects of arsenic trioxide (As2O3) and to develop means and ways to enhance its antitumor properties. As2O3 is a heavy metal derivative with potent antileukemic activities in vitro and in vivo and it is highly effective in the treatment of patients with acute promyelocytic leukemia (APL). Despite advances in the field and the high interest to expand the use of arsenic to other hematological malignancies, the precise mechanisms by which As2O3 induces antileukemic responses are not known. We have provided the first evidence that As2O3 -induced autophagy is essential for generation of its suppressive effects on primitive leukemic progenitors from patients with myeloid leukemias. The current proposal is a systematic approach to define the cellular events that lead to As2O3 -dependent autophagy and to identify the mechanisms of autophagy-mediated degradation of oncogenic proteins in primitive leukemic precursors and leukemia initiating stem cells (LICs). Specific aim 1 will examine the mechanisms of As2O3 -autophagy in leukemic progenitor cells. Studies will be performed to identify upstream kinases in the autophagic cascade in leukemia cells and to define the sequence of events leading to their activation in response to arsenic. Other studies will examine the relationship of autophagy with cellular negative feedback regulatory pathways (NFRPs) that are induced in response to As2O3. Specific aim 2 will identify effector mechanisms by which autophagy mediates arsenic- responses on primitive progenitors and leukemia initiating stem cells from patients with AML and CML. Experiments will be performed to define whether autophagy mediates arsenic-dependent degradation of different oncoproteins and to define the precise mechanisms by which this occurs. Other studies will determine whether pharmacological or molecular targeting of elements of the autophagic machinery can enhance arsenic-induced suppression of primitive leukemic precursors and LICs. Specific aim 3 will examine the role of autophagy in arsenic-dependent antileukemic responses in different leukemia mouse models in vivo. It involves experiments to determine whether autophagy is required for the antileukemic properties of As2O3 in vivo and to examine whether other inducers of autophagy exhibit synergistic antileukemic activities with As2O3. Altogether, this work will advance our understanding of the mechanisms by which As2O3 generates antileukemic responses. It should have important clinical-translational implications and possibly lead to the development of novel approaches to target early progenitors and LICs using combinations of As2O3 with other autophagy inducers. PUBLIC HEALTH RELEVANCE: Arsenic trioxide is a heavy metal derivative that exhibits important antileukemic effects in vitro and in vivo. This agent has major clinical activity in the treatment of acute promyelocytic leukemia (APL) and is approved by the FDA for the treatment of patients suffering from this subtype of AML. Despite the extensive clinical use of arsenic, the precise mechanisms by which it induces antileukemic responses are not known. Our studies have provided evidence that arsenic induces autophagic leukemic cell death and have suggested a potential mechanism by which it may target and eliminate leukemic stem cells (LIC), involving autophagic degradation of transforming oncoproteins. The work of this proposal will precisely determine the role of autophagy in arsenic- dependent LIC targeting using in vitro and in vivo models. It will also determine whether combinations of arsenic with other autophagy inducers provide an effective mode to eliminate primitive leukemia precursors and LICs.