(HealthDay News) — In mice prone to developing lung cancer, supplementation with antioxidants increases tumor growth, according to a study published in the Jan. 29 issue of Science Translational Medicine.

Volkan I. Sayin, from the University of Gothenburg in Sweden, and colleagues supplemented the diets of mice prone to developing lung cancer with the antioxidants N-acetylcysteine and vitamin E, which are structurally unrelated. The authors note that clinical trials in humans have suggested that antioxidants do not protect against lung cancer.

The researchers found that both antioxidants led to changes in gene expression, particularly a suppression of antioxidant genes. Both increased the growth of lung cancer cells by reducing reactive oxygen species, DNA damage, and p53 expression. The effect of antioxidants on tumor growth could be reproduced by inactivating p53. The authors note that, in high-risk populations such as smokers, who are more likely to have tumors or precancerous lesions, oxidants such as N-acetylcysteine given to reduce mucus production may increase tumor growth.

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“This study demonstrates that antioxidant supplementation of the diet reduces reactive oxygen species and DNA damage, prevents p53 activation, and markedly increases tumor cell proliferation and tumor growth in mice,” Sayin and colleagues conclude. “The data demonstrate that tumor cells proliferate faster when oxidative stress is suppressed.”

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