NEW YORK (Reuters Health) – Parenteral treatment with vitamin C can reduce the growth of aggressive tumor xenografts in mice, according to a report in the August 4th Early Edition of the Proceedings of the National Academy of Sciences.

Although vitamin C is typically thought of as an antioxidant, Dr. Mark Levine and colleagues show in the new study that it can also act as a prooxidant. The results also indicate that at pharmacologic levels, the essential nutrient elicits hydrogen peroxide-dependent cytotoxicity only toward cancer cells, leaving normal cells unscathed.

Testing in mice with glioblastoma xenografts showed that a single parenteral dose of vitamin C leads to free radical formation in tumor interstitial fluids, but not in the blood, Dr. Levine, from National Institutes of Health in Bethesda, Maryland, and co-authors found.

Daily treatment with vitamin C significantly slowed the growth of glioblastoma, ovarian cancer, and pancreatic cancer in mice.

To gauge the therapeutic potential of vitamin C, the researchers administered the nutrient intravenously to humans and found that concentrations corresponding to the efficacious levels in mice were, in fact, achievable.

Despite these encouraging results, the authors note that “use of pharmacologic ascorbate as a single agent was not curative.” Still, they believe that it could be used in combination with other therapies to increase the efficacy against prognostically poor malignancies, such as those examined in the study.

Proc Natl Acad Sci USA 2008.