Enhancing Metabolic Oxidative Stress and Therapy Responses in Cancer Stem Cells

描述（由申请人提供）：现代癌症疗法的发展基于这样的想法，即抗癌剂应通过利用癌细胞特异性的生物化学和生理学差异来选择性地杀死癌症细胞而不是正常细胞。早期祖细胞“癌症干细胞”（CSC）可能代表导致治疗失败的癌细胞亚群的概念也获得了重要的实验支持。此外，癌症和正常细胞之间氧化代谢的根本差异似乎导致活性氧（ROS; O2. -）和H2O2），并且可以代表用于选择性增强治疗反应的"靶标"。如果CSC的存活可以通过选择性地增强ROS的产生同时抑制氢过氧化物代谢而受到损害，那么CSC代谢的差异可以被利用来选择性地改善对常规放射化学疗法的响应。初步数据显示，来自人乳腺癌人群的早期祖细胞CSC表现出稳态O2？相对于来源于正常乳腺上皮细胞群的干细胞。此外，ROS水平的药理学操作[用线粒体靶向的三苯基膦衍生物; TPP]和/或谷胱甘肽（GSH）-和硫氧还蛋白（Trx）-依赖性氢过氧化物代谢的抑制[使用丁硫酰亚胺亚砜（BSO）和金诺芬（AUR）]显示出通过诱导代谢氧化应激相对于正常干细胞选择性地消耗CSC。最后，TPP衍生物在动物中耐受性良好，同时抑制GSH和Trx依赖性氢过氧化物代谢（AUR + BSO）增强了CSC对辐射的反应。这些初步数据导致了一种假设，即旨在增加线粒体ROS产生的药理学操作（使用TPP衍生物）与GSH和Trx依赖性氢过氧化物代谢的抑制剂相结合，将在CSC（与正常干细胞相比）中引起选择性细胞毒性，并通过增加O2？和H2O2介导的氧化应激。这一假设将在两个目标中进行检验，以：1）确定TPP衍生物的药理学操作是否会通过增加线粒体O2？2）确定与TPP衍生物组合的GSH-和Trx-依赖性氢过氧化物代谢的同时抑制是否可以通过增加O2？和H2O2介导的氧化应激。完成这些研究将提供一个详细的机制的理解，使用线粒体ROS的操作与氢过氧化物代谢抑制剂的组合，以选择性地杀死癌症干细胞的潜力。这项工作解决了癌症生物学中的一个关键问题，这是利用干细胞氧化代谢改变来增强癌症治疗所必需的。

DESCRIPTION (provided by applicant): The development of modern cancer therapies is predicated on the idea that anticancer agents should selectively kill cancer vs. normal cells by exploiting biochemical and physiological differences specific to cancer cells. The notion that early progenitor "cancer stem cells" (CSCs) may represent a subpopulation of cancer cells contributing to treatment failure has also gained significant experimental support. Furthermore, fundamental differences in oxidative metabolism between cancer and normal cells appear to lead to increased steady-state levels of reactive oxygen species (ROS; O2.- and H2O2) and may represent a "target" for selectively enhancing therapeutic responses. If survival of CSCs could be compromised by selectively enhancing the production of ROS while inhibiting hydroperoxide metabolism, then differences in CSC metabolism could be exploited to selectively improve responses to conventional radio-chemo-therapies. Preliminary data shows that early progenitor CSCs from human breast carcinoma population exhibit increased steady-state levels of O2?- relative to stem cells derived from normal breast epithelial cell populations. In addition, pharmacological manipulations of ROS levels [with mitochondrial targeted triphenylphosphonium derivatives; TPP] and/or inhibition of glutathione (GSH)- and thioredoxin (Trx)- dependent hydroperoxide metabolism [using buthionine sulfoximine (BSO) and Auranofin (AUR)] is shown to selectively deplete CSCs, relative to normal stem cells by inducing metabolic oxidative stress. Finally, TPP derivatives are well tolerated in animals and simultaneous inhibition of GSH- and Trx-dependent hydroperoxide metabolism (AUR+BSO) enhances CSCs responses to radiation. These preliminary data led to the hypothesis that pharmacological manipulations designed to increase mitochondrial ROS production (with TPP derivatives) combined with inhibitors of GSH- and Trx- dependent hydroperoxide metabolism will cause selective cytotoxicity in CSCs (vs. normal stem cells) as well as enhance tumor responses to radio-chemo-therapies by increasing O2?- and H2O2-mediated oxidative stress. This hypothesis will be tested in two Aims to: 1) Determine if pharmacological manipulations with TPP derivatives will selectively enhance oxidative stress as well as chemo-radio-sensitivity by increasing mitochondrial O2?- and H2O2 in cancer vs. normal stem cells in vitro and in vivo and 2) Determine if simultaneous inhibition of GSH- and Trx-dependent hydroperoxide metabolism combined with TPP derivatives can selectively sensitize cancer vs. normal stem cells to chemo- or radio-sensitivity by increasing O2?- and H2O2-mediated oxidative stress. Completing these studies will provide a detailed mechanistic understanding of the potential for using manipulations of mitochondrial ROS in combination with inhibitors of hydroperoxide metabolism to selectively kill cancer stem cells. This work addresses a critical question in cancer biology necessary for exploiting altered stem cell oxidative metabolism to enhance cancer therapy.