Project 3: MRI Imaging of Redox Active Fe Predicts GBM Responses to Pharmacological Ascorbate

项目概要/摘要-项目3： 多形性胶质母细胞瘤（GBM）是美国最常见的恶性脑肿瘤，但尽管 侵袭性治疗GBM预后差，中位总生存期约为15个月。调查人员 在项目3中已经发现药理学抗坏血酸盐（P-AscH-）是一种有前途化疗-放疗辅助剂 利用氧化代谢的根本差异进行GBM治疗。初步数据显示， 相对于正常人星形胶质细胞（NHA），P-AscH-对GBM细胞的选择性毒性通过H2 O2诱导的 由氧化还原活性铁离子介导的氧化应激。此外，在临床前GBM模型中以及在 1期临床试验（NCT 01752491），他们发现P-AscH-（达到~20 mM [血浆]）+辐射和 替莫唑胺治疗耐受性良好，不良事件最少，同时显示出令人鼓舞的治疗效果。 应答最后，初步数据也支持磁共振（MR）成像可能是 能够检测Fe的氧化还原状态（即，Fe+2/Fe+3）用于预测对P-AscH-组合的响应 通过评估T2* 弛豫测定法的变化与化学-放射治疗相结合。 目前，对引起GBM与GBM的不同敏感性的机制还没有清楚的了解。 正常脑细胞转化为P-AscH项目3将检验P-AscH选择性增加的假设， 相对于正常星形胶质细胞，人GBM细胞中不稳定的氧化还原活性Fe相关的H2 O2形成， 导致氧化性DNA损伤增加和GBM细胞对辐射的敏感性增加， 替莫唑胺，可以在体内使用MR成像与T2* 弛豫和定量 磁化率作图目的1将确定P-AscH诱导的细胞内[H2 O2]介导的 患者来源的前神经、神经、经典和间充质GBM细胞的化学-放射增敏作用 通过增强的DNA双链断裂和差异， 在GBM细胞中H2 O2代谢。目的2将确定增加的不稳定铁池（LIP）是否介导了 GBM相对于NHA对P-AscH诱导的化学-放射增敏的敏感性。Aim 3将在原位确定 GBM异种移植模型，如果P-AscH诱导的氧化还原活性LIP的调节和选择性敏化， 使用T2* MRI成像和定量敏感性绘图可以预测放疗和化疗 以及标准的生化分析。目标的完成将定义生物化学机制 潜在的P-AscH-介导的体外和体内原位GBM细胞的选择性化学-放射增敏 模型以及研究高度创新的MR成像方法来预测反应。项目3是 也很好地融入了PO 1的总体主题，为利用基本的 氧化还原代谢的差异，以改善癌症患者使用P-AscH-的治疗效果。

Project Summary/Abstract - Project 3: Glioblastoma multiforme (GBM) is the most common malignant brain tumor in the United States but despite the aggressive treatment GBM has a dismal prognosis with a median overall survival of ~15 months. Investigators in Project 3 have found that pharmacological ascorbate (P-AscH-), is a promising adjuvant to chemo-radiation therapy in GBM exploiting fundamental differences in oxidative metabolism. Preliminary data demonstrate the selective toxicity of P-AscH- to GBM cells, relative to normal human astrocytes (NHA), occurs via H2O2-induced oxidative stress mediated by redox active Fe ions. Furthermore, in a pre-clinical GBM model as well as in a phase 1 clinical trial (NCT01752491), they found that P-AscH- (achieving ~20 mM [plasma]) + radiation and temozolomide therapy was well-tolerated with minimal adverse events while showing encouraging therapeutic responses. Finally, preliminary data also support the idea that magnetic resonance (MR) imaging may be capable of detecting the redox state of Fe (i.e., Fe+2/Fe+3) for predicting responses to P-AscH- in combination with chemo-radiation therapy via assessing changes of T2* relaxometry. Currently, there is no clear understanding of mechanisms causing the differential susceptibility of GBM vs. normal brain cells to P-AscH- in vivo. Project 3 will test the hypothesis that P-AscH- selectively increases labile redox active Fe associated H2O2 formation in human GBM cells, relative to normal astrocytes, leading to increased oxidative DNA damage and increased sensitivity of GBM cells to radiation and temozolomide that can be assessed in vivo using MR imaging with T2* relaxometry and quantitative susceptibility mapping. Aim 1 will determine if P-AscH--induced increases in intracellular [H2O2] mediate chemo-radiosensitization in patient derived GBM cells of Proneural, Neural, Classical and Meschymal subtypes relative to normal human astrocytes (NHA) via enhanced DNA double strand breaks and differences in H2O2 metabolism in GBM cells. Aim 2 will determine if increased labile iron pools (LIP) mediate the sensitivity of GBM vs. NHA to P-AscH--induced chemo-radiosensitization. Aim 3 will determine in orthotopic GBM xenograft models if P-AscH- induced regulation of the redox-active LIP and selective sensitization to radiation and chemotherapy can be predicted using T2* MRI imaging and quantitative susceptibility mapping as well as standard biochemical assays. Completion of the aims will define biochemical mechanisms underlying P-AscH--mediated selective chemo-radiosensitization of GBM cells in vitro and in vivo orthotopic models as well as investigating highly innovative MR imaging approaches to predict responses. Project 3 is also well-integrated into the overall theme of the PO1 to provide a new paradigm for exploiting fundamental differences in redox metabolism to improve treatment efficacy in cancer patients using P-AscH-.