Exposure to Antioxidants Accelerates Malignant Melanoma Metastasis

Antioxidants, which had been shown previously to stimulate lung cancer growth, have now been found to accelerate metastasis of malignant melanoma.

Investigators at the University of Gothenburg (Sweden), who had reported in 2014 that antioxidants hastened and aggravated the progression of lung cancer in mice, worked with both a mouse model and with human malignant melanoma cell cultures in a follow-up study.

The investigators showed in this study, which was published in the October 7, 2015, issue of the journal Science Translational Medicine, that administration of the antioxidant N-acetylcysteine (NAC) increased lymph node metastases in an endogenous mouse model of malignant melanoma but had no impact on the number and size of primary tumors. Similarly, NAC and the soluble vitamin E analog Trolox markedly increased the migration and invasive properties of human malignant melanoma cells but did not affect their proliferation. Both antioxidants increased the ratio between reduced and oxidized glutathione in melanoma cells and in lymph node metastases. The increased migration depended on new glutathione synthesis.

"As opposed to the lung cancer studies, the primary melanoma tumor was not affected," said senior author Dr. Martin Bergö, a professor in the department of internal molecular and clinical medicine at the University of Gothenburg. "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. Granted that lung cancer is the most common form of the disease 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."

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