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October 14, 2015

Antioxidant Use May Promote Melanoma Metastasis

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    Results from a new study suggest that cancer patients should not supplement their diet with large doses of antioxidants. [grThirteen/iStock]

    Decades ago Nobel laureate and American chemist Linus Pauling espoused the benefits of taking megadoses of vitamin C to prevent and treat various diseases. This controversial practice has led many to promote the taking of antioxidant supplements to prevent everything from the common cold to cancer and has become an almost engrained practice for individual healthcare—unfortunately, with little scientific evidence to support the ritual.  

    Now, researchers at the Children’s Research Institute at UT Southwestern (CRI) has uncovered evidence that suggests cancer cells benefit more from antioxidants than normal cells, raising concerns about the use of dietary antioxidant supplements by patients with cancer.  

    The investigators utilized a specialized mice model that had been transplanted with melanoma cells from patients, which previous work showed recapitulated metastasis of human melanoma cells and was predictive of their metastasis in patients. The CRI team found that when antioxidants were administered to the mice, the cancer spread more quickly than in mice that did not get antioxidants.  

    “We discovered that metastasizing melanoma cells experience very high levels of oxidative stress, which leads to the death of most metastasizing cells,” explained senior author Sean Morrison, Ph.D., CRI director and chair in pediatric genetics at UT Southwestern Medical Center. “Administration of antioxidants to the mice allowed more of the metastasizing melanoma cells to survive, increasing metastatic disease burden.”

    The findings from this study were published online today in Nature through an article entitled “Oxidative stress inhibits distant metastasis by human melanoma cells.”

    It has long been known that the spread of cancer cells from one part of the body to another is an inefficient process in which the vast majority of cancer cells that enter the blood fail to survive, due to the highly oxidative environment and exposure to immune cells.

    “The idea that antioxidants are good for you has been so strong that there have been clinical trials done in which cancer patients were administered antioxidants,” noted Dr. Morrison. “Some of those trials had to be stopped because the patients getting the antioxidants were dying faster. Our data suggest the reason for this: cancer cells benefit more from antioxidants than normal cells do.”

    The CRI researchers were intrigued by their findings and acknowledged that although the study's results have not yet been tested in people, they surmise that cancer should be treated with pro-oxidants and that cancer patients should not supplement their diet with large doses of antioxidants.  

    “This finding also opens up the possibility that when treating cancer, we should test whether increasing oxidative stress through the use of pro-oxidants would prevent metastasis,” Dr. Morrison stated. “One potential approach is to target the folate pathway that melanoma cells use to survive oxidative stress, which would increase the level of oxidative stress in the cancer cells.”

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