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

描述(申请人提供)：肿瘤细胞对高水平的过渡元素铁上瘾，这是铁依赖酶功能所必需的，使肿瘤细胞快速分裂和生长。当不适当地隔离时，铁具有高度的氧化还原活性，并可以催化形成有毒的活性氧物种，从而破坏细胞。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通路激活在许多癌症中是一种常见的事件，目前用现有的药物难以治疗。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的突变选择性地杀死各种人类肿瘤细胞。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，利用了在这些肿瘤细胞中发现的高水平的细胞内铁。在这里，我将重点放在一种RSL的致死机制上，Erastin。使用RNA干扰(RNAi)筛选，我确定了11个与Erastin诱导的死亡有关的基因，其中包括未鉴定的基因ACSF2。我假设ACSF2通过调节胞质铁水平和依赖于血红素的NADPH氧化酶1(NOX1)复合体活性来调节铁结合分子(铁载体)的产生，而铁结合分子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基因敲除小鼠身上通过细胞死亡、铁代谢、NOX活性、铁载体产生和异种移植瘤生长的遗传、生化和化学分析来验证这一假设。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，深入了解铁载体介导的铁摄取在肿瘤细胞生长中的作用，并显著提高我们靶向细胞铁成瘾的能力，从而在RAS途径突变的癌症中实现肿瘤选择性细胞死亡。 公共卫生相关性：拟议的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来选择性地 杀死这些细胞。这一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存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.