–Clinical trials suggest that 800 — 1000 times the daily recommended amount of vitamin C is safe for brain and lung cancer patients.
– Vitamin C, even at high levels, isn’t toxic to normal cells.
In a work presented March 30, 2017 in Cancer Cell, University of Iowa researchers also show pathways by which altered iron metabolism in cancer cells, and not normal cells, lead to increased sensitivity to cancer cell death caused by high dose vitamin C.Co-author, who was one of the first to propose that cancer cells might have a vulnerability to redox active compounds over 40 years ago, Garry Buettner, said: “This paper reveals a metabolic frailty in cancer cells that is based on their own production of oxidizing agents that allows us to utilize existing redox active compounds, like vitamin C, to sensitize cancer cells to radiation and chemotherapy.” Buettner, along with study senior authors Bryan Allen and Douglas Spitz, are faculty members at the University of Iowa’s Department of Radiation Oncology, Free Radical and Radiation Biology Programme, in the Holden Comprehensive Cancer Center.
The research group at Iowa found, however, that tumor tissue’s abnormally high levels of redox active iron molecules (a by-product of abnormal mitochondrial metabolism) react with vitamin C to form hydrogen peroxide and free radicals derived from hydrogen peroxide. These free radicals are believed to cause DNA damage selectively in cancer cells (versus normal cells) leading to enhanced cancer cell death as well as sensitization to radiation and chemotherapy in cancer cells.
Co-senior and author, who focused on the biochemical studies, Douglas Spitz, said: “This is a significant example of how knowing details of potential mechanisms and the basic science of redox active compounds in cancer versus normal cells can be leveraged clinically in cancer therapy. Here, we verified convincingly that increased redox active metal ions in cancer cells were responsible for this differential sensitivity of cancer versus normal cells to very high doses of vitamin C.”
Co-senior author, who led the clinical side of the study, Bryan Allen, said: “The majority of cancer patients we work with are excited to participate in clinical trials that could benefit future patient outcomes down the line. Results look promising but we’re not going to know if this approach really improves therapy response until we complete these phase II trials.”