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

项目概要/摘要-项目4：闪光效应的机理基础：O2的作用 最近，在几种动物模型中获得的令人兴奋和意想不到的新数据有力地支持了超 高剂量率照射称为FLASH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 用于改善放射治疗效果。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上，即碳氧（95%O2; 5%CO2）呼吸显著减少了 保护正常脑组织，同时增强肿瘤的反应。这一结果以及理论 考虑到癌症与正常组织中O2的不同氧化还原反应， 研究O2作为正常和癌组织对FLASH-RT的不同反应的驱动因素的反应。 这些考虑导致了项目4的中心假设，即有机物的差异代谢 在FLASH-RT后，癌症与正常组织中的氢过氧化物（ROOH）， 不稳定的铁池和脂质过氧化链反应，介导肿瘤与 正常组织进行FLASH-RT。该假设将在以下目的中得到支持： 具体目标1：确定动物呼吸的O2张力的变化如何改变动物呼吸器官的结构完整性。 血管，成熟神经元形态，炎症反应的激活，以及 FLASH-RT与常规剂量率暴露。 具体目标2：确定使用Oxylite进行FLASH-RT后肿瘤与正常组织中的O2变化 测量与ROOH和动物脂质过氧化下游产物的测量相关 在观察到正常组织保留的剂量下暴露于FLASH-RT的组织。 具体目标3：确定有机氢过氧化物和氧化还原活性金属离子在 使用药理学和遗传学方法， 操纵谷胱甘肽过氧化物酶（GPx）1和4以及抑制Fe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明确定义生物化学机制 包括有机氢过氧化物代谢和氧化还原活性铁代谢的选择性保留 在脑癌治疗的小鼠模型中， 使用FLASH-RT利用癌症与正常细胞代谢的根本差异， 治疗效果，同时保护正常组织。 整合到P01中：项目4将通过提供基因操纵的基因，与P01中的所有项目相互作用。 条件性过表达GPx 1和GPx 4以及铁蛋白的脑癌细胞，以及 氧化应激用于在FLASH-RT模型中测试氧化代谢机制。

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.