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”，铁依赖酶的功能是必需的，铁依赖酶能够使肿瘤细胞快速分裂和生长。如果隔离不当，铁具有高度的氧化还原活性，可以催化形成破坏细胞的有毒活性氧。因此，通过释放这种元素的氧化还原活性，有可能以一种选择性的方式杀死肿瘤细胞。RAS-RAF-MEK通路激活是目前难以用现有药物治疗的许多癌症的常见事件。我们之前发现了几种小分子化合物，它们通过激活这一途径中的突变，选择性地杀死多种人类肿瘤细胞。这些ras选择性致死（RSL）化合物似乎触发了一种新的细胞死亡形式，利用这些肿瘤细胞中发现的高水平的细胞内铁。在这里，我主要关注一种RSL的致死机制，即擦除素。通过RNA干扰（RNAi）筛选，我确定了11个基因，包括未表征的基因ACSF2。我假设ACSF2通过调节胞质铁水平和血红素依赖性NADPH氧化酶1 （NOX1）复合物活性来调节铁结合分子（铁载体）的产生，铁载体是肿瘤细胞快速增殖和erastin致死效应所必需的。我将在人类肿瘤细胞和Acsf2敲除小鼠中测试这一假设，使用细胞死亡、铁代谢、氮氧化物活性、铁载体产生和异种移植肿瘤生长的遗传、生化和化学分析。这项工作将定义由erastin和类似化合物触发的新的细胞死亡途径，为铁载体介导的铁摄取在肿瘤细胞生长中的作用提供见解，并显著提高我们靶向细胞铁成瘾以实现RAS途径突变癌症中肿瘤选择性细胞死亡的能力。

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.