Dual Oxidase-Induced Sustained Generation of Hydrogen Peroxide Contributes to Pharmacological Ascorbate-Induced Cytotoxicity

Pharmacological ascorbate treatment (P-AscH-, high-dose, intravenous vitamin C) results in a transient short-term increase in the flux of hydrogen peroxide that is preferentially cytotoxic to cancer cells vs. normal cells. This study examines whether an increase in hydrogen peroxide is sustained post-treatment and potential mechanisms involved in this process. Cellular bioenergetic profiling following treatment with P-AscH- was examined in tumorigenic and non-tumorigenic cells. P-AscH- resulted in sustained increases in the rate of cellular oxygen consumption (OCR) and reactive oxygen species (ROS) in tumor cells with no changes in non-tumorigenic cells. Sources for this increase in ROS and OCR were DUOX 1 and 2, which are silenced in PDAC, but upregulated with P-AscH- treatment. An inducible catalase system, to test causality for the role of hydrogen peroxide, reversed the P-AscH--induced increases in DUOX, while DUOX inhibition partially rescued P-AscH--induced toxicity. In addition, DUOX was significantly downregulated in pancreatic cancer specimens compared to normal pancreas tissues. Together these results suggest that P-AscH--induced toxicity may be enhanced by late metabolic shifts in tumor cells resulting in a feed-forward mechanism for generation of hydrogen peroxide and induction of metabolic stress through enhanced DUOX expression and rate of oxygen consumption.