By Admin at 12 Apr 2017, 16:41 PM

Researchers have now gained greater insights into how vitamin C may be harnessed to kill cancer cells, courtesy of a new study co-funded by Gateway for Cancer Research. High-dose vitamin C has been considered as a cancer treatment since the 1970s. [1] When consumed at healthy dietary concentrations, the vitamin has valuable antioxidant properties.

However, when administered at higher therapeutic doses, well above those obtained through dietary intake, and which can only be achieved through intravenous (not oral) administration, the breakdown of vitamin C generates hydrogen peroxide, which can damage tissue and DNA.

The study revealed that intravenous delivery of high-dose vitamin C can produce a high flux of hydrogen peroxide in tumors. Further, cancer cells are much more susceptible to damage from hydrogen peroxide than healthy cells, in part because the former tend to have lower levels of an enzyme called catalase, which cells use for detoxifying high concentrations of hydrogen peroxide.

Study author Garry Buettner, a University of Iowa redox biology expert, said in a news release:

“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 … 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.” [2]

Cells with lower catalase activity were more easily damaged and killed by high-dose vitamin C, and the study revealed that the rate of hydrogen peroxide removal in normal cells was, on average, 2-fold higher than in cancer cells.

The use of intravenous high-dose vitamin C in combination with standard chemotherapy or radiation is being tested in a Gateway-funded clinical trial for pancreatic cancer to determine if it improves patient survival. Other trials, not funded by Gateway, are also testing the protocol in lung cancers. Previous research already showed the combination to be safe and well tolerated and also suggested it may improve patient outcomes.

The featured study results suggest that cancers with low levels of catalase may be most responsive to high-dose vitamin C therapy, while cancers with high levels may be least responsive, according to Buettner.

The researchers hope to develop ways to measure catalase levels in tumors to determine which patients could benefit most from high-dose vitamin C. “This information can also be used in finding combination therapies that may increase the efficacy of treatment for those tumors with higher catalase activities,” the researchers concluded.

Sources
1. Cancer.gov
2. Iowa Now January 10, 2017
Redox Biology December 2016

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