In 2005, Andrew Morris and his colleagues at the University of Dundee in the United Kingdom were following up on therapy for type 2 diabetes patients when they reported results that have since set the world of cancer research abuzz. They found that use of an insulin-lowering drug known as metformin was associated with a significant decrease in cancer incidence. Since then, half a dozen studies have confirmed it: Diabetics treated with metformin have from 25% to 40% less cancer than those who receive insulin as therapy or take sul-fonylurea drugs that increase insulin secretion from the pancreas. The idea that reducing insulin and insulin-like hormones in circulation may prevent tumors has become a bright hope for drug research. A host of insulin-suppressing drugs are in the pharmaceutical industry pipeline, says Lewis Cantley, director of the Cancer Center at Beth Israel Deaconess Medical Center, which is part of Harvard Medical School in Boston. But the companies may have been beaten to the punch: "Metformin may have already saved more people from cancer deaths than any drug in history," he says. It is one of the oldest and most commonly prescribed antidiabetic therapies in the world; some 120 million prescriptions are written for it yearly.
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