While antioxidants can neutralize the cancer-catalyzing effects of free radicals, some recent studies have suggested that if cancer is already present, antioxidants may spur its proliferation.
For the study, researchers focused on two diabetic medications — saxagliptin and sitagliptin — and an antioxidant supplement called alpha-lipoic acid, which is commonly prescribed to diabetics to treat nephropathy.
The team began by analyzing past clinical trials involving the medications, searching for any indication that they increased cancer risk. Nothing caught their attention. They then exposed human liver, breast, colon, ovarian and other cancer cells to the drugs, which seemed to make it easier for the cells to migrate. In a follow-up study, nine mice with human tumors were treated with either one of the medications or a benign saline solution daily for six weeks. Those given medications had expanded metastasis when compared to the saline control group.
The study’s results suggest future medical dilemmas. Diabetics — who are already at higher risk for cancer — are often prescribed medications with antioxidant properties because free radicals are thought to be particularly harmful for them because they lead to cell dysfunction and vascular problems.
David Nathan, MD, director of the diabetes center at Massachusetts General Hospital in Boston, told Science by email that he would be wary of frightening patients with these findings, saying “the message may mutate into a general fear of diabetes drugs.”
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