Targeting Tumor Cell Iron Addiction to Achieve Tumor-Selective Cell Death

描述（由申请人提供）：肿瘤细胞对高水平的过渡元素铁“上瘾”，这是使肿瘤细胞快速分裂和生长的铁依赖性酶的功能所必需的。当螯合不当时，铁是高度氧化还原活性的，可以催化破坏细胞的有毒活性氧的形成。因此，通过释放这种元素的氧化还原活性，应该可以选择性地杀死肿瘤细胞。RAS-RAF-MEK通路激活是目前难以用现有药物治疗的许多癌症中的常见事件。我们先前鉴定了几种小分子化合物，它们选择性地杀死在该途径中具有激活突变的各种人类肿瘤细胞。这些RAS选择性致死（RSL）化合物似乎引发了一种新形式的细胞死亡，这种细胞死亡利用了这些肿瘤细胞中发现的高水平细胞内铁。在这里，我专注于一个RSL的致命机制，erastin。使用RNA干扰（RNAi）筛选，我确定了11个基因所需的erastin诱导的死亡，包括未表征的基因ACSF 2。我推测ACSF 2通过调节胞浆铁水平和血红素依赖性NADPH氧化酶1（NOX 1）复合物活性，调节铁结合分子（铁载体）的产生，这是快速肿瘤细胞增殖和erastin致死效应所必需的。我将在人类肿瘤细胞和Acsf 2基因敲除小鼠中使用细胞死亡、铁代谢、NOX活性、铁载体产生和异种移植肿瘤生长的遗传、生化和化学测定来检验这一假设。这项工作将定义由erastin和类似化合物触发的新型细胞死亡途径，深入了解铁载体介导的铁摄取在肿瘤细胞生长中的作用，并显着提高我们靶向细胞铁成瘾的能力，以实现RAS途径突变型癌症的肿瘤选择性细胞死亡。 公共卫生相关性：这项研究将确定一类新的候选抗肿瘤药物如何利用在许多肿瘤细胞中发现的高水平铁， 杀死这些细胞。这些知识将为新的治疗方法开辟道路，并提高我们对铁在肿瘤细胞生命和死亡中的作用的理解。

DESCRIPTION (provided by applicant): Tumor cells are 'addicted' to high levels of the transition element iron, which is necessary for the function of iron-dependent enzymes that enable rapid tumor cell division and growth. When improperly sequestered, iron is highly redox active and can catalyze the formation of toxic reactive oxygen species that destroy the cell. It should therefore be possible to kill tumor cells in a selective way by unleashing the redox activity of this element. RAS-RAF-MEK pathway activation is a common event in many cancers that is currently difficult to treat with existing drugs. We previously identified several small molecule compounds that selectively kill a variety of human tumor cells with activating mutations in this pathway. These RAS-selective lethal (RSL) compounds appear to trigger a new form of cell death that exploits the high levels of intracellular iron found in these tumor cells. Here I focus on the lethal mechanism of one RSL, erastin. Using RNA interference (RNAi) screening I identified 11 genes required for erastin-induced death, including the uncharacterized gene ACSF2. I hypothesize that ACSF2 regulates the production of an iron-binding molecule (siderophore) that is necessary for rapid tumor cell proliferation and for the lethal effects of erastin, via regulation of cytosolic iron levels and heme-dependent NADPH oxidase 1 (NOX1) complex activity. I will test this hypothesis in human tumor cells and in Acsf2 knockout mice using genetic, biochemical and chemical assays of cell death, iron metabolism, NOX activity, siderophore production and xenograft tumor growth. This work will define the novel cell death pathway triggered by erastin and similar compounds, provide insight into the role of siderophore-mediated iron uptake in tumor cell growth and significantly improve our ability to target cellular iron addiction to achieve tumor-selective cell death in RAS pathway mutant cancers. PUBLIC HEALTH RELEVANCE: The proposed studies will determine how a new class of candidate anti-tumor drugs exploit the high levels of iron found in many tumor cells to selectively kill these cells. This knowledge will open the way to new therapeutic approaches and improve our understanding of the role of iron in tumor cell life and death.