Project 4: Mechanistic Basics of FLASH Effect: Role of O2

项目摘要/摘要-项目4：闪光效果的机理基础：O2的作用 最近，几个动物模型中令人兴奋和意想不到的新数据有力地支持了这样一个前提，即超 高剂量率照射被称为闪光放射治疗(Flash-RT)，可导致正常 组织，同时保留肿瘤反应，有效地导致治疗窗口的显著增加 以改善放射治疗结果。然而，这种效应的机制目前尚不清楚。项目4 将建立在令人兴奋的初步数据基础上，即Carbogen(95%O2；5%CO2)呼吸显著减少 在保护正常脑组织的同时增强对肿瘤的反应。这一结果以及理论上的 考虑到癌症组织和正常组织中O2的不同氧化还原反应提供了动力 研究氧作为正常组织和肿瘤组织对闪光放射治疗差异反应的驱动因素的反应。 这些考虑导致了项目4中的中心假设，即有机物质的差异代谢 闪光放射治疗后癌组织和正常组织中的过氧化氢(Rooh)，由不同的 不稳定的铁库和脂质过氧化链式反应，介导了肿瘤和癌症的不同反应。 对正常组织进行闪光放射治疗。这一假设将在以下目标中得到追求： 具体目标1：确定动物呼吸的氧气张力的变化如何改变大脑结构的完整性 血管系统，成熟神经元形态，炎症反应的激活，以及神经认知的影响 闪光照射与传统剂量率照射的比较。 特定目标2：确定使用Oxylite的闪光放射治疗后肿瘤组织与正常组织相比是否存在O2变化 测量结果与动物体内氧自由基及其下游脂质过氧化产物的测量结果相关 组织暴露在闪光-RT的剂量，观察到正常的组织保留。 具体目标3：确定有机过氧化氢和氧化还原活性金属离子在 用药理学和遗传学方法研究肿瘤与正常组织的区别敏感性 操纵谷胱甘肽过氧化物酶(GPX)1和4，以及抑制铁氧化还原循环的金属螯合剂。 科学影响：该项目的成功完成将清楚地定义生化机制 涉及有机过氧化氢代谢和氧化还原活性铁代谢，是选择性节育的基础 闪光放射治疗小鼠脑癌模型中正常组织的研究以及提供一个新的范例 使用Flash-RT利用癌症和正常细胞代谢的根本差异来增加 在保护正常组织的同时达到治疗效果。 融入P01：项目4将通过提供基因操纵的 有条件地过表达GPX1和4以及铁蛋白和验证的生物标志物的脑癌细胞 氧化应激用于检测Flash-RT模型中氧化代谢的机制。

Project Summary/Abstract - Project 4: Mechanistic Basics of FLASH Effect: Role of O2 Recently, exciting and unexpected new data in several animal models strongly supports the premise that ultra- high dose rate irradiation termed FLASH radiotherapy (FLASH-RT) can result in significant sparing of normal tissue while preserving tumor responses, effectively leading to significant increases in the therapeutic window for improving radiotherapy outcomes. However, the mechanisms for this effect are currently unknown. Project 4 will build on the exciting preliminary data that carbogen (95% O2; 5% CO2) breathing significantly diminished the protection of normal brain tissue while enhancing the responses of tumors. This result as well as theoretical considerations of the differential redox reactions of O2 in cancer versus normal tissues provides the impetus to study the reactions of O2 as drivers of the differential responses of normal and cancer tissue to FLASH-RT. These considerations have led to the central hypothesis in Project 4 that differential metabolism of organic hydroperoxides (ROOH) in cancer versus normal tissues following FLASH-RT, caused by differences in labile Fe pools and lipid peroxidation chain reactions, mediates the differential responses of tumor vs. normal tissues to FLASH-RT. This hypothesis will be pursed in the following Aims: Specific Aim 1: Determine how varying the O2 tension that animals breathe alters the structural integrity of the vasculature, mature neuronal morphology, activation of inflammatory responses, and neurocognitive effects of FLASH-RT versus conventional dose rate exposure. Specific Aim 2: Determine if changes in O2 in tumor versus normal tissues following FLASH-RT using Oxylite measurements correlate with measurements of ROOH and downstream products of lipid peroxidation in animal tissues exposed to FLASH-RT at doses where normal tissue sparing is observed. Specific Aim 3: Determine the causal involvement of organic hydroperoxides and redox active metal ions in the differential sensitivity of tumor versus normal tissues using pharmacological and genetic approaches to manipulate glutathione peroxidases (GPx) 1 and 4 as well as metal chelators that inhibit Fe redox cycling. Scientific Impact: The successful completion of this project will clearly define biochemical mechanisms involving organic hydroperoxide metabolism and redox active iron metabolism underlying the selective sparing of normal tissues from FLASH-RT in mouse models of brain cancer therapy as well as providing a new paradigm for using FLASH-RT to exploit fundamental differences in cancer vs. normal cell metabolism for increasing treatment efficacy while protecting normal tissues. Integration into the P01: Project 4 will interact with all projects in the P01 by providing genetically manipulated brain cancer cells that conditionally overexpress GPx 1 and 4 as well as ferritin and validated biomarkers of oxidative stress for testing mechanisms of oxidative metabolism in models of FLASH-RT.