August 5, 2008
Vitamin C Injections Slow Tumor Growth in Mice
Vitamin C injections slow tumor growth in mice WASHINGTON, Aug. 4 (Xinhua) -- High-dose injections of vitamin C, also known as ascorbate or ascorbic acid, reduced tumor weight and growth rate by about 50 percent in mouse models of brain, ovarian, and pancreatic cancers, researchers from the U.S. National Institutes of Health (NIH) report on Monday.
The researchers traced ascorbate's anti-cancer effect to the formation of hydrogen peroxide in the extracellular fluid surrounding the tumors. Normal cells were unaffected. These results will appear in the Aug. 5 issue of the Proceedings of the National Academy of Sciences.
Natural physiologic controls precisely regulate the amount of ascorbate absorbed by the body when it is taken orally. To bypass these normal controls, NIH scientists injected ascorbate into the veins or abdominal cavities of rodents with aggressive brain, ovarian, and pancreatic tumors.
By doing so, they were able to deliver high doses of ascorbate, up to 4 grams per kilogram of body weight daily. "At these high injected doses, we hoped to see drug-like activity that might be useful in cancer treatment," said Mark Levine, the study's lead author.
Vitamin C plays a critical role in health, and a prolonged deficiency leads to scurvy and eventually to death. Vitamin C may also act as an antioxidant, protecting cells from the damaging effects of free radicals.
The NIH researchers, however, tested the idea that ascorbate, when injected at high doses, may have prooxidant instead of antioxidant activity. Prooxidants would generate free radicals and the formation of hydrogen peroxide, which, the scientists hypothesized, might kill tumor cells.
In their laboratory experiments on 43 cancer and 5 normal cell lines, the researchers discovered that high concentrations of ascorbate had anticancer effects in 75 percent of cancer cell lines tested, while sparing normal cells. In their paper, the researchers also showed that these high ascorbate concentrations could be achieved in people.
The team then tested ascorbate injections in immune-deficient mice with rapidly spreading ovarian, pancreatic, and brain tumors. The ascorbate injections reduced tumor growth and weight by 41 to 53 percent. "These pre-clinical data provide the first firm basis for advancing pharmacologic ascorbate in cancer treatment in humans," the researchers conclude.
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