Selenium Modulates Cancer Cell Response to Pharmacologic Ascorbate

Area of Science:

• Redox biology
• Cancer therapy
• Nutritional biochemistry

Background:

• High-dose ascorbate (vitamin C) exhibits anticancer properties.
• Proposed mechanisms include hydrogen peroxide generation or glutathione depletion.
• The precise redox mechanisms and modulators are not fully elucidated.

Purpose of the Study:

• To elucidate the specific redox mechanisms underlying high-dose ascorbate's anticancer effects.
• To investigate the role of selenium in mediating ascorbate's cytotoxicity and anticancer activity.
• To explore the potential of dietary selenium modulation for enhancing cancer therapy.

Main Methods:

• In vitro studies assessing ascorbate's metabolic effects and cytotoxicity.
• Investigation of selenium's modulatory role using selenoenzymes (GPX1, GPX4) and NADPH.
• In vivo experiments using dietary selenium deficiency in glioblastoma xenograft mouse models.

Main Results:

• Ascorbate's cytotoxic and metabolic effects are mediated by hydrogen peroxide, independent of dehydroascorbate.
• Antioxidant selenoenzymes, particularly GPX1, suppressed ascorbate's effects, powered by NADPH.
• Dietary selenium deficiency significantly enhanced ascorbate's efficacy against glioblastoma in vivo.

Conclusions:

• Selenoproteins are critical regulators of cancer redox homeostasis.
• Cancer sensitivity to ascorbate and other free radical-inducing therapies is influenced by selenium status.
• Dietary selenium manipulation offers a potential strategy to improve the efficacy of pro-oxidant cancer therapies.