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Enhanced Pharmacological Ascorbate Oxidation Radiosensitizes Pancreatic Cancer
Journal article   Peer reviewed

Enhanced Pharmacological Ascorbate Oxidation Radiosensitizes Pancreatic Cancer

Matthew S Alexander, Brianne R O'Leary, Justin G Wilkes, Adrienne R Gibson, Brett A Wagner, Juan Du, Ehab Sarsour, Rosa F Hwang, Garry R Buettner and Joseph J Cullen
Radiation research, Vol.191(1), pp.43-51
01/2019
DOI: 10.1667/RR15189.1
PMCID: PMC6441967
PMID: 30376411

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Abstract

Pharmacologic ascorbate (P-AscH ) is emerging as a promising adjuvant for advanced pancreatic cancer. P-AscH generates hydrogen peroxide (H O ), leading to selective cancer cell cytotoxicity. Catalytic manganoporphyrins, such as MnT4MPyP, can increase the rate of oxidation of P-AscH , thereby increasing the flux of H O , resulting in increased cytotoxicity. We hypothesized that a multimodal treatment approach, utilizing a combination of P-AscH , ionizing radiation and MnT4MPyP, would result in significant flux of H O and pancreatic cancer cytotoxicity. P-AscH with MnT4MPyP increased the rate of oxidation of P-AscH and produced radiosensitization in all pancreatic cancer cell lines tested. Three-dimensional (3D) cell cultures demonstrated resistance to P-AscH , radiation or MnT4MPyP treatments alone; however, combined treatment with P-AscH and MnT4MPyP resulted in the inhibition of tumor growth, particularly when also combined with radiation. In vivo experiments using a murine model demonstrated an increased rate of ascorbate oxidation when combinations of P-AscH with MnT4MPyP were given, thus acting as a radiosensitizer. The translational potential was demonstrated by measuring increased ascorbate oxidation ex vivo, whereby MnT4MPyP was added exogenously to plasma samples from patients treated with P-AscH and radiation. Combination treatment utilizing P-AscH , manganoporphyrin and radiation results in significant cytotoxicity secondary to enhanced ascorbate oxidation and an increased flux of H O . This multimodal approach has the potential to be an effective treatment for pancreatic ductal adenocarcinoma.
Pancreatic Neoplasms - metabolism Electron Spin Resonance Spectroscopy Oxidation-Reduction Humans Pancreatic Neoplasms - pathology Pancreatic Neoplasms - radiotherapy Ascorbic Acid - metabolism Drug Synergism Pancreatic Neoplasms - drug therapy Metalloporphyrins - therapeutic use Animals Radiation-Sensitizing Agents - metabolism Cell Line, Tumor Disease Models, Animal

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