PUBLICDOMAINIMAGES, DEBORA CARTAGENA UCSDCPFor the second time this month, scientists have reported that antioxidant supplementation sped up cancer growth in mice with melanoma. In the latest study, published this week (October 14) in Nature, researchers fed mice a common dietary supplement and the animals ended up with more tumors and more widespread cancers.
“We discovered that metastasizing melanoma cells experience very high levels of oxidative stress, which leads to the death of most metastasizing cells,” Sean Morrison, director of the Children’s Medical Center Research Institute at University of Texas Southwestern Medical Center, said in a press release. “Administration of antioxidants to the mice allowed more of the metastasizing melanoma cells to survive, increasing metastatic disease burden.”
Morrison’s group gave mice N-acetylcysteine (NAC), an antioxidant used in some body-building supplements. In a study published last week (October 7) in Science Translational Medicine, Martin Bergo’s team at the University of Gothenburg in Sweden also gave mice with melanoma NAC and discovered twice as many lymph node metastases as mice on a normal diet.
“The challenges will be to understand how generally applicable are these observations to other tumor types and to translate these findings into clinically useful dietary guidelines,” Dimitrios Anastasiou, who studies cancer metabolism at the U.K.’s Francis Crick Institute and who was not involved in either study, told The Scientist earlier this month.
In 2014, Bergo’s group gave NAC to mice with lung cancer. Compared to control mice, the dosed mice developed larger tumors and they died sooner. The team showed that antioxidants reduced potentially damaging reactive oxygen species in tumor cells and reduced the activity of a tumor suppressor called p53.
“This is an extremely striking observation, but not surprising given the rather disappointing outcomes of patients at risk for developing lung cancer who had been treated with various antioxidants,” David Tuveson of Cold Spring Harbor Laboratory who was not involved in the work, told The Scientist at the time. “We should now consider whether people consuming high doses of antioxidants are ironically promoting cancers that they seek to prevent.”
Morrison told The Washington Post: “Personally, from the results we’ve seen, I would avoid supplementing my diet with large amounts of antioxidants if I had cancer.” He said cancer patients should continue eating antioxidants as part of a healthy diet.