Pharmacological Ascorbic Acid and Hyperbaric Oxygen Therapy Target Tumor Cell Metabolism via an Oxidative Stress Mechanism

High-dose ascorbic acid (AA) is an anti-carcinogenic, minimally toxic, metabolic therapy that targets tumor cell metabolism via an oxidative stress (OxS) mechanism. At pharmacological levels (achieved i.v.), AA delivers H2O2 to tumorous tissue upon oxidation, initiating cell death. High-dose AA has shown significant anticancer effects in vitro, in vivo, and in small-scale human reports at concentrations nontoxic to normal cells, thus having great potential as an adjuvant to the standard of care. Hyperbaric oxygen therapy (HBOT) is another non-toxic, pro-oxidative, metabolic therapy that delivers 100% oxygen at elevated barometric pressure, elevating tissue pO2 and oxygenating hypoxic tumor cells, which, when coupled with high levels of reactive oxygen and nitrogen species present in cancer cells, can further augment OxS and lead to cell death. We hypothesized that AA would induce ROS-dependent OxS and that this would be further augmented with HBOT. This study’s aims were as follows (1) to examine the anticancer effect of AA in vitro, (2) to evaluate the mechanism of AA-induced OxS, (3) to determine if HBOT and AA are synergistic.

To characterize the anticancer effects of AA in vitro, we measured cell viability and proliferation following treatment with graded concentrations of AA in mouse brain tumor-derived VM-M3 cells. We found that AA mediates cell death in a concentration-dependent manner, and that concentrations great than or equal to 0.5mM AA significantly induced cell death compared to control. We also found that concentrations > 0.05mM AA inhibit cell proliferation compared to control and 0.01mM AA at 72 and 96 hours of growth. To investigate the role of OxS in AA-induced cytotoxicity, we measured VM-M3 cell viability in the presence of AA and antioxidant N-Acetylcysteine (NAC), and found that treatment with 0.5 and 5mM NAC attenuates the OxS-induced cytotoxic effect of AA. To determine if HBOT can enhance the therapeutic effect of AA, we measured VM-M3 cell viability following treatment with HBOT and AA. We found that HBOT significantly enhanced the cytotoxic effect of 0.3mM AA.

This data indicates that AA exhibits anti-cancer effects in vitro through an OxS mechanism and that HBOT can enhance this therapeutic effect. Evidence supports the use of these minimally toxic, pro-oxidative, metabolic therapies as adjuvants to the current standard of care.