Antioxidants Speed Up Lung Cancer Progression

A new study from Sweden concluded that antioxidants, which are often thought to have cancer-fighting abilities, significantly accelerate lung cancer progression. “It is fairly well established that free radicals can induce DNA damage and that DNA damage can induce cancer,” said senior author Martin O. Bergo, Sahlgrenska Cancer Center, University of Gothenburg, Gothenburg, Sweden. “This dogma has led to the notion that antioxidants must protect against cancer.” He explained that when this notion was analyzed in large clinical trials, however, researchers found that antioxidants either had no impact or worsened cancer risk. The current study “provides experimental support for a decades-long puzzle from clinical trials with antioxidants and proposes a surprisingly simple mechanism for the effect,” said Bergo. “It is also important because despite the lack of clinical evidence that antioxidants protect against cancer, people across the globe pin their hopes of staying cancer-free to antioxidant supplements.” He noted that this is the first study to specifically examine the impact of antioxidants on existing tumors in state-of-the-art mouse models of lung cancer. “Most studies have been designed to look at the ability of antioxidants to affect a future risk of developing cancer,” he pointed out. Tumor progression was tracked in two groups of mice with lung cancer: one group received supplemental antioxidants in the form of vitamin E and N-acetylcysteine and the other group received no additional antioxidants in their diets. The antioxidants were administered in doses that were equivalent to a dose that a person would get from an ordinary multivitamin. “The effect of the antioxidants was dose-dependent and observed with two unrelated antioxidants in two different mouse models of lung cancer,” noted Bergo. “Tumor burden increased between 2- and 3-fold, and the mice died in half the time if they received antioxidants in their drinking water or in their food.” In addition, the mice that received additional antioxidants had bigger tumors than the control mice. Bergo explained that antioxidants accelerate tumor growth by reducing reactive oxygen species and DNA damage within the tumor cells. “Thus, just as antioxidants are thought to protect healthy cells from becoming cancer cells in the future, antioxidants protect the tumor cell by removing potentially harmful free radicals,” he said. Researchers confirmed their results using human lung cancer cells. “Although the study was performed in mice, we saw similar effects in lung cancer cells from human patients,” said Bergo. “If you combine this information with the results of the previous clinical trials showing that antioxidants increases lung cancer risk in humans, one could make some suggestions.” The results suggest, for example, that individuals with lung cancer or those who are at increased risk of developing lung cancer (eg, smokers, ex-smokers, patients with chronic obstructive pulmonary disease [COPD]) may want to use antioxidant supplements with caution, Bergo told Consultant360. “People at risk of lung cancer could potentially have a small undiagnosed tumor that is triggered into growing faster by the extra antioxidants,” he added. “But perhaps the most urgent clinical implication comes from the fact that patients with COPD take acetylcysteine to relieve mucus production and improve their breathing. Acetylcysteine is a potent antioxidant, and patients with COPD are often smokers with an increased risk of developing lung cancer. Therefore, acetylcysteine use in this patient group needs to be discussed and studied further,” Bergo stated. This study was published in Science Translational Medicine. -Meredith Edwards White Reference Sayin VI, Ibrahim MX, Larsson E, Nilsson JA, Lindahl P, Bergo MO. Antioxidants accelerate lung cancer progression in mice. Sci Transl Med. 2014 Jan 29;6(221):221ra15. doi: 10.1126/scitranslmed.3007653.