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Antioxidants May Increase the Rate of Metastasis, Protect Existing Tumors in Malignant Melanoma

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Key Points

  • As opposed to the previous lung cancer studies, the primary melanoma tumor was not affected, but the antioxidant boosted the ability of the tumor cells to metastasize.
  • Antioxidants protect healthy cells from free radicals that can turn them into malignancies but may also protect a tumor once it has developed. Taking nutritional supplements containing antioxidants may unintentionally hasten the progression of a small tumor or premalignant lesion.
  • Antioxidants that pertain to melanoma may be not only digested but also absorbed cutaneously in the cases of sunscreen or lotion.

Fresh research at Sahlgrenska Academy has found that antioxidants can double the rate of melanoma metastasis in mice. The results reinforce previous findings that antioxidants hasten the progression of lung cancer. According to Martin Bergö, PhD, people with cancer or an elevated risk of developing the disease should avoid nutritional supplements that contain antioxidants. These findings were published by Le Gal et al in Science Translational Medicine.

Lung Cancer Findings

Researchers at Sahlgrenska demonstrated in January 2014 that antioxidants hastened and aggravated the progression of lung cancer. Mice that were given antioxidants developed additional and more aggressive tumors. Experiments on human lung cancer cells confirmed the results.

Given well-established evidence that free radicals can cause cancer, the research community had simply assumed that antioxidants, which destroy them, provide protection against the disease. Found in many nutritional supplements, antioxidants are widely marketed as a means of preventing cancer. Because the lung cancer studies called the collective wisdom into question, they attracted a great deal of attention.

“As opposed to the lung cancer studies, the primary melanoma tumor was not affected,” said Dr. Bergö. “But the antioxidant boosted the ability of the tumor cells to metastasize—an even more serious problem because metastasis is the cause of death in the case of melanoma. The primary tumor is not dangerous per se and is usually removed.”

Experiments on cell cultures from patients with malignant melanoma confirmed the new results.

“We have demonstrated that antioxidants promote the progression of cancer in at least two different ways,” said Dr. Bergö.

Melanoma Study Findings

The overall conclusion from the various studies is that antioxidants protect healthy cells from free radicals that can turn them into malignancies but may also protect a tumor once it has developed. Taking nutritional supplements containing antioxidants may unintentionally hasten the progression of a small tumor or premalignant lesion, neither of which is possible to detect.

“Previous research at Sahlgrenska Academy has indicated that cancer patients are particularly prone to take supplements containing antioxidants,” said Dr. Bergö. “Our current research combined with information from large clinical trials with antioxidants suggests that people who have been recently diagnosed with cancer should avoid such supplements.”

The role of antioxidants is particularly relevant in the case of melanoma, not only because melanoma cells are known to be sensitive to free radicals, but because the cells can be exposed to antioxidants by nondietary means as well.

“Skin and suntan lotions sometimes contain beta carotene or vitamin E, both of which could potentially affect malignant melanoma cells in the same way as antioxidants in nutritional supplements,” said Dr. Bergö. How antioxidants in lotions affect the course of malignant melanoma is currently being explored.

“We are testing whether antioxidants applied directly to malignant melanoma cells in mice hasten the progression of cancer in the same way as their dietary counterparts,” Dr. Bergö said.

He stresses that additional research is badly needed. “Granted that lung cancer is the most common form of [cancer] and melanoma is expanding fastest, other forms of cancer and types of antioxidants need to be considered if we want to make a fully informed assessment of the role that free radicals and antioxidants play in the process of cancer progression.”

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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