Why high-dose vitamin C kills cancer cells

January 9, 2017, University of Iowa
Model of a vitamin C molecule. Black is carbon, red is oxygen, and white is hydrogen. Credit: Public Domain

Vitamin C has a patchy history as a cancer therapy, but researchers at the University of Iowa believe that is because it has often been used in a way that guarantees failure.

Most C therapies involve taking the substance orally. However, the UI scientists have shown that giving vitamin C intravenously—and bypassing normal gut metabolism and excretion pathways—creates blood levels that are 100 - 500 times higher than levels seen with oral ingestion. It is this super-high concentration in the blood that is crucial to vitamin C's ability to attack .

Earlier work by UI redox biology expert Garry Buettner found that at these extremely high levels (in the millimolar range), vitamin C selectively kills cancer cells but not in the test tube and in mice. Physicians at UI Hospitals and Clinics are now testing the approach in clinical trials for pancreatic cancer and lung cancer that combine high-dose, intravenous vitamin C with standard chemotherapy or radiation. Earlier phase 1 trials indicated this treatment is safe and well-tolerated and hinted that the therapy improves patient outcomes. The current, larger trials aim to determine if the treatment improves survival.

In a new study, published recently in the December issue of the journal Redox Biology, Buettner and his colleagues have homed in on the biological details of how high-dose vitamin C (also known as ascorbate) kills cancer cells.

The study shows that vitamin C breaks down easily, generating , a so-called reactive oxygen species that can damage tissue and DNA. The study also shows that tumor cells are much less capable of removing the damaging hydrogen peroxide than normal cells.

"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 inclusion of high-dose ascorbate in the treatment.

"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.

Explore further: Vitamin C may enhance radiation therapy for aggressive brain tumors

More information: Claire M. Doskey et al, Tumor cells have decreased ability to metabolize H2O2: Implications for pharmacological ascorbate in cancer therapy, Redox Biology (2016). DOI: 10.1016/j.redox.2016.10.010

Related Stories

Vitamin C may enhance radiation therapy for aggressive brain tumors

February 17, 2012
Recent research by the University of Otago, Wellington has shown that giving brain cancer cells high dose vitamin C makes them much more susceptible to radiation therapy.

Sunlight offers surprise benefit—it energizes infection fighting T cells

December 20, 2016
Sunlight allows us to make vitamin D, credited with healthier living, but a surprise research finding could reveal another powerful benefit of getting some sun.

Low vitamin D levels linked to increased risk of bladder cancer

November 8, 2016
Vitamin D deficiency is associated with an increased risk of developing bladder cancer, according to a systematic review of seven studies presented today at the Society for Endocrinology annual conference in Brighton. Though ...

Intravenous vitamin C may boost chemo's cancer-fighting power

February 5, 2014
(HealthDay)—Large doses of intravenous vitamin C have the potential to boost chemotherapy's ability to kill cancer cells, according to new laboratory research involving human cells and mice.

Recommended for you

Single-cell study in a childhood brain tumor affirms the importance of context

April 20, 2018
In defining the cellular context of diffuse midline gliomas, researchers find the cells fueling their growth and suggest a potential approach to treating them: forcing their cells to be more mature.

Aggressive breast cancer already has resistant tumour cells prior to chemotherapy

April 20, 2018
Difficult to treat and aggressive "triple-negative" breast cancer is chemoresistant even before chemotherapy begins, a new study by researchers from Karolinska Institutet and the University of Texas MD Anderson Cancer Center ...

Mechanism that drives development of liver cancer brought on by non-alcoholic fatty liver disease discovered

April 19, 2018
A team of researchers from several institutions in China has found a mechanism that appears to drive the development of a type of liver cancer not caused by alcohol consumption. In their paper published in the journal Science ...

Discovery adds to evidence that some children are predisposed to develop leukemia

April 19, 2018
St. Jude Children's Research Hospital researchers have made a discovery that expands the list of genes to include when screening individuals for possible increased susceptibility to childhood leukemia. The finding is reported ...

Scientists identify 170 potential lung cancer drug targets using unique cellular library

April 19, 2018
After testing more than 200,000 chemical compounds, UT Southwestern's Simmons Cancer Center researchers have identified 170 chemicals that are potential candidates for development into drug therapies for lung cancer.

Chip-based blood test for multiple myeloma could make bone biopsies a relic of the past

April 19, 2018
The diagnosis and treatment of multiple myeloma, a cancer affecting plasma cells, traditionally forces patients to suffer through a painful bone biopsy. During that procedure, doctors insert a bone-biopsy needle through an ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.