“In this paper we demonstrate that cancer cells are much less efficient in removing hydrogen peroxide than normal cells. Thus, cancer cells are much more prone to damage and death from a high amount of hydrogen peroxide,” says Buettner, a professor of radiation oncology and a member of Holden Comprehensive Cancer Center at the University of Iowa. “This explains how the very, very high levels of vitamin C used in our clinical trials do not affect normal tissue, but can be damaging to tumor tissue.”
Normal cells have several ways to remove hydrogen peroxide, keeping it at very low levels so it does not cause damage. The new study shows that an enzyme called catalase is the central route for removing hydrogen peroxide generated by decomposing vitamin C. The researchers discovered that cells with lower amounts of catalase activity were more susceptible to damage and death when they were exposed to high amounts of vitamin C.
Buettner says this fundamental information might help determine which cancers and which therapies could be improved by including high-dose vitamin C in the treatment regimen.
“Our results suggest that cancers with low levels of catalase are likely to be the most responsive to high-dose vitamin C therapy, whereas cancers with relatively high levels of catalase may be the least responsive,” he explains.
A future goal of the research is to develop methods to measure catalase levels in tumors.
In addition to Buettner, the UI research team included Claire Doskey (now doing postdoctoral work at Michigan State University), Visarut Buranasudja, Brett Wagner, Justin Wilkes, Juan Du, and Joseph Cullen. The study was funded in part by grants from the National Institutes of Health and the Gateway for Cancer Research.