Study shows antioxidants speed-up the metastasis of malignant melanoma.


There is well-established evidence that free radicals can cause cancer so researchers had 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.  Now, a study from researchers at the University of Gothenburg has shown that antioxidants can double the rate of melanoma metastasis in mice. The team state that their results show that people with cancer, or an elevated risk of developing the disease, should avoid nutritional supplements that contain antioxidants.

Previous studies show that antioxidants protect healthy cells from free radicals that can turn them into malignancies, however, they may also protect a tumour 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.

Earlier studies from the team demonstrated that antioxidants hastened and aggravated the progression of lung cancer. Mice that were given antioxidants developed additional and more aggressive tumors with experiments on human lung cancer cells confirming the results.  The lab state that their lung cancer studies attracted a great deal of attention as it indicated that cancer patients are particularly prone to take supplements containing antioxidants. The current study suggests that people who have been recently diagnosed with cancer should avoid such supplements.

The current study shows that antioxidants double the rate of metastasis in malignant melanoma, the most perilous type of skin cancer.  The group observed that, as opposed to their previous lung cancer studies, the primary melanoma tumour was not affected.  However, results show that the antioxidant boosted the ability of the tumour cells to metastasize, an even more serious problem because metastasis is the cause of death in the case of melanoma.  Data findings from cell cultures from patients with malignant melanoma confirmed the new results, showing that antioxidants promote the progression of cancer in at least two different ways.

The lab explain that the role of antioxidants is particularly relevant in the case of melanoma due to the fact melanoma cells are known to be sensitive to free radicals and the cells can be exposed to antioxidants by non-dietary means as well.  They go on to add that 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.  The group stress that additional research is badly needed.

The team surmise that other forms of cancer and types of antioxidants need to be considered if the global medical community want to make a fully informed assessment of the role that free radicals and antioxidants play in the process of cancer progression.  For the future, how antioxidants in lotions affect the course of malignant melanoma is currently being explored with the researchers testing whether antioxidants applied directly to malignant melanoma cells in mice hasten the progression of cancer in the same way as their dietary counterparts.

Source:  Sahlgrenska Academy, University of Gothenburg

Human malignant melanoma cell viewed through a fluorescent, laser-scanning confocal microscope. Invasive structures involved in metastasis appear as greenish-yellow dots, while actin (green) and vinculin (red) are components of the cell’s cytoskeleton.  Credit: Vira V. Artym, National Institute of Dental and Craniofacial Research, NIH.

Human malignant melanoma cell viewed through a fluorescent, laser-scanning confocal microscope. Invasive structures involved in metastasis appear as greenish-yellow dots, while actin (green) and vinculin (red) are components of the cell’s cytoskeleton. Credit: Vira V. Artym, National Institute of Dental and Craniofacial Research, NIH.

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