Mechanisms of ascorbate-induced cytotoxicity in pancreatic cancer

描述（由申请人提供）：静脉注射抗坏血酸（抗坏血酸，维生素C），而不是口服抗坏血酸，可产生高血浆浓度，对胰腺癌细胞具有细胞毒性。虽然抗坏血酸已被用于癌症治疗，但其作用机制尚不清楚。我们小组最近的研究表明，抗坏血酸在胰腺癌细胞中诱导细胞毒性和氧化应激，并且这种细胞毒性在肿瘤细胞中比在正常细胞中更为突出。药理学上，抗坏血酸已被假设为过氧化氢（H2O2）形成的前药。H2O2可直接损伤线粒体，使ATP产生减少。抗坏血酸诱导的氧化应激可能代表了肿瘤细胞和正常细胞代谢之间的差异，这种差异可以通过操纵来改善癌症治疗。为了了解抗坏血酸诱导胰腺癌细胞氧化应激的机制，我们将验证H2O2的产生介导胰腺癌细胞相对于正常人类细胞对抗坏血酸诱导的代谢氧化应激的易感性增加的假设。我们将用以下三个具体目标来检验我们的假设：1。确定药物抗坏血酸诱导的细胞毒性是否由于胰腺癌细胞线粒体对H2O2的敏感性导致ATP产生减少。2. 确定体外和体内人类胰腺癌细胞中增加氢过氧化物和/或氢过氧化物解毒化学抑制剂产生的化合物是否可以增强药理学抗坏血酸诱导的细胞毒性。3. 确定抗坏血酸诱导的细胞毒性是否可以通过化疗药物（吉西他滨，5-FU）在体外和体内对人胰腺癌细胞增强。如果我们能够严格证明抗坏血酸在人类胰腺癌细胞中诱导比正常人类细胞类型更优先的细胞毒性和氧化应激，并且这依赖于H2O2产量的增加，然后，本研究计划的结果将为合理设计基于正常细胞和胰腺癌细胞氧化代谢生物化学基本差异的联合癌症治疗模式提供基础。公共卫生相关性：静脉注射抗坏血酸产生对胰腺肿瘤细胞具有细胞毒性的高血浆浓度。药理学上，抗坏血酸已被假设为过氧化氢（H2O2）形成的前药。H2O2可直接损伤线粒体，使ATP产生减少。我们的建议是研究抗坏血酸诱导胰腺癌细胞毒性的机制。

DESCRIPTION (provided by applicant): Intravenous ascorbate (ascorbic acid, vitamin C), but not oral ascorbate, produces high plasma concentrations in the range that is cytotoxic to pancreatic cancer cells. Though ascorbate has been utilized in cancer therapy, little is known about the mechanism of action. Recent studies from our group have demonstrated that ascorbate induces cytotoxicity and oxidative stress in pancreatic cancer cells and this cytotoxicity appears to be more prominent in tumor vs. normal cells. Pharmacological ascorbate has been hypothesized to be a pro-drug for formation of hydrogen peroxide (H2O2). H2O2 may directly damage mitochondria so that ATP production decreases. Ascorbate-induced oxidative stress could represent a difference between tumor cell and normal cell metabolism amenable to manipulations designed to improve cancer therapy. To gain a mechanistic understanding of ascorbate-induced oxidative stress in pancreatic cancer cells, we will test the hypothesis that production of H2O2 mediates the increased susceptibility of pancreatic cancer cells to ascorbate-induced metabolic oxidative stress, relative to normal human cells. We will test our hypothesis with the following three Specific Aims: 1. Determine if pharmacological ascorbate-induced cytotoxicity is due to pancreatic cancer cell mitochondria sensitivity to H2O2 resulting in decreased ATP production. 2. Determine if pharmacological ascorbate-induced cytotoxicity can be enhanced by compounds that increase the production of hydroperoxides and/or chemical inhibitors of hydroperoxide detoxification in human pancreatic cancer cells in vitro and in vivo. 3. Determine if pharmacological ascorbate-induced cytotoxicity can be enhanced by chemo- therapeutic agents (gemcitabine, 5-FU) in human pancreatic cancer cells in vitro and in vivo. If we can rigorously demonstrate that pharmacological ascorbate induces preferential cytotoxicity and oxidative stress in human pancreatic cancer cells vs. normal human cell types and that this is dependent on the increased production of H2O2, then the results of this proposed research program will provide a foundation for the rational design of a combined modality cancer therapy based on a fundamental difference between the biochemistry of oxidative metabolism in normal vs. pancreatic cancer cells. PUBLIC HEALTH RELEVANCE: Intravenous ascorbate produces high plasma concentrations in the range that is cytotoxic to pancreatic tumor cells. Pharmacological ascorbate has been hypothesized to be a pro-drug for formation of hydrogen peroxide (H2O2). H2O2 may directly damage mitochondria so that ATP production decreases. Our proposal investigates the mechanism by which ascorbate-induces cytotoxicity in pancreatic cancer cells.