Research has been increasingly challenging the conventional health food-store wisdom about antioxidants — that they can prevent cancer, slow aging, and work all sorts of other miracles. Now, a study published on Wednesday supports the idea that antioxidants can fuel the spread of cancer cells. Scientists in China and the United States found that two popular drugs for type 2 diabetes, both of which happen to be antioxidants, goose cancer metastasis in lab mice.
You’ll want to know:
There is no question that antioxidants, such as those in fruits and vegetables and other foods, neutralize molecules called free radicals that can damage DNA. That has led to assertions that antioxidants can prevent cancer, since DNA damage can turn normal cells into malignant ones. But studies of whether antioxidant supplements (pills, not foods) can prevent cancer have largely disappointed.
Because free radicals might also attack cancer cells, scientists are studying whether antioxidants might allow tumors to flourish. The new research, in Science Translational Medicine, found that they can. When scientists exposed lab dishes of human cancer cells (liver, breast, colon, ovarian) to the diabetes drugs sitagliptin (sold by Merck as Januvia) and saxagliptin (AstraZeneca’s Onglyza), the cells migrated more. And when nine mice with human tumors were given either of the drugs, the cells metastasized more and invaded far-flung tissue, said senior author Hongting Zheng, an endocrinologist at Third Military Medical University in Chongqing, China. The drugs did not raise the risk of developing cancer.
Why it matters:
If the findings hold up, it will be more evidence that antioxidants have a dark side. That doesn’t mean people with diabetes should stop taking their medications. But even at this early stage, some experts say if such patients also have cancer it’s worth a conversation with their doctor about whether it makes sense to switch to different diabetes medications. A 2015 case report described how a patient with a rare cancer experienced more serious metastasis after receiving saxagliptin. (AstraZeneca did not reply to requests for comment on the new study.)
What they’re saying:
This is not the first animal research to link antioxidants to metastasis. A 2015 study in mice found that antioxidants seem to help melanoma cells spread. “This is in line with our work and others’,” said biologist Zachary Schafer of the University of Notre Dame, who led a 2013 study showing that antioxidants can fuel the spread of breast cancer cells in mice. “These are really profound data, and their results are scientifically compelling. The major advance here is showing that antidiabetes agents can drive a very specific anti-oxidant pathway that in turn drives metastasis.”
But keep in mind:
It’s a mouse study. But the usual caveat here — the finding needs to be confirmed in people — is not too helpful. Clinical trials leading to the approval of diabetes drugs do not include cancer patients, so any metastasis-promoting effect of the drugs wouldn’t have shown up in those trials. It’s hard to imagine a study intentionally exposing people with both diabetes and cancer to these drugs.
The bottom line:
Nature gave us and other animals free radicals for a reason. The headlong rush to mess with them is looking more and more like a bad idea.