High-dose vitamin C causes cancer cells to die in a cell culture model. These experiments revealed the mechanism of action by which vitamin C achieves this.1
As vitamin C breaks down, it generates hydrogen peroxide. Hydrogen peroxide is a reactive oxygen species that can cause cellular and DNA damage. Tumor cells are less able to remove hydrogen peroxide due to low levels of catalase, an enzyme that removes hydrogen peroxide.
“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,” said senior author Garry Buettner, PhD, a professor of radiation oncology and a member of Holden Comprehensive Cancer Center at the University of Iowa in Iowa City, 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.”
Intravenous delivery of vitamin C can bypass the gut metabolism and excretion pathway, resulting in serum levels that are 100 to 500 times higher than serum levels after oral ingestion. At this higher serum level, vitamin C could cause the selective death of cancer cells over healthy cells.
Clinical trials are underway at the University of Iowa Hospitals and Clinics, testing high doses of vitamin C delivered intravenously with standard chemotherapy in patients with pancreatic cancer and with lung cancer.
This research used 15 different tumor cell lines and 10 different normal cell lines. Results indicated tumor lines with lower levels of catalase died more upon vitamin C administration than tumor lines with higher levels of catalase.
“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,” explained Dr Buettner.
These researchers want to develop methods for measuring catalase levels in tumors to determine which are most likely to respond to intravenous administration of high-dose vitamin C.
1. Doskey CM, Buranasudja V, Wagner BA, et al. Tumor cells have decreased ability to metabolize H2O2: implications for pharmacological ascorbate in cancer therapy. Redox Biol. 2016 Dec. doi: 10.1016/j.redox.2016.10.010