Antioxidants are supposed to keep your cells healthy. That is why millions of people gobble supplements like vitamin E and beta-carotene each year. Today, however, a new study adds to a growing body of research suggesting these supplement actually have a harmful effect in one serious disease cancer.
The work, conducted in mice, shows that antioxidants can change cells in way that fuel the spread of malignant melanoma-the most serious skin cancer- to different parts of the body. The progression makes the disease even more deadly.
But scientists now think that antioxidants, at high enough levels, also protect cancer cells from these same free radicals
For the new study, published in Science Translational Medicine, Martin Bergo, a cell biologist at the University of Gothenburg’s Sahlgrenska Cancer Center in Sweden, and his colleagues decided to look at melanoma because rates have been increasing and because the cancer is known to be sensitive to the effect of free radicals. They fed the antioxidant N-acetylcysteine(NAC) to mice that had been genetically engineered to be susceptible to melanoma. The per-weight dose they gave the mice was consistent with what people typically consume in supplements. Although the treated mice did not develop more skin tumor than similar mice that had not been fed the antioxidants, they developed twice as many tumors un their lymph nodes, a hallmark of the spread of cancer-a process called NAC or a form of vitamin E to cultured human melanoma cells, they confirmed that the antioxidants improved the cells’ability to move and invade a nearby membrane.
Antioxidants may bolster protection of these dangerous cells. Bergo and his colleagues found higher levels of glutathione, an antioxidant made by the body, inside metastatic tumor cells in treated mice compared with untreated mice. The treated mice also had a higher ratio of glutathione to glutathione disulfide, the molecule that glutathione become after it neutralizes free radicals. These findings suggest that when the body is given extra antioxidants, its tumor cells get to keep more of the antioxidants that they already make themselves.
The substances may help cancer cells in other ways, too. Previous research has suggested that glutathione affects the activity of a protein called RhoA, which help cells move to different parts of the body.
In their 2014 lung cancer study they also found that antioxidant supplements caused lung tumor cells to turn off the activity of a well-known cancer-suppressing gene called p53 ;its inactivation is believed to drive metastasis. And Schafer’s work has shown that antioxidants help migrating breast cancer cells survive when they detach from the extracellular matrix, the network of protein surrounding cells.
It is possible that the supplements did not triggercancer but rather accelerated the progression of existing undiagnosed cancers, making later discovery of the disease likely.
The medical advice for people at this point is tentative. More studies need to be done to bolter this hypothesis and understand exactly how antioxidants affect cancer cells in humans.
His results do have a silver lining. They suggest a potential new way to target the disease. If cancer is very sensitive to the damaging effect if free radicals, then it might be possible to develop drugs that target cancer cells specifically and prevent them from producing antioxidants or that ramp up free radical levels inside of the malignant cells, exploiting their newly discovered weakness.