How Diabetes Drug May Prevent Cancer

Metformin for type 2 diabetes may reduce cancer risk by preventing DNA damage

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Back in 2005, Scottish researchers found surprisingly low rates of cancer among diabetes patients taking metformin, one of the most commonly used drugs for treating type 2 diabetes. Now, we may know why this happens.

People who take metformin may be partially protected against cancer. Exposure to this common diabetes drug reduces the mutation of cells and the buildup of DNA damage, both of which are involved in the development of cancer.

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After the Scottish researchers found that diabetes patients taking metformin had very low rates of cancer, a series of follow-up studies ensued. These other studies had similar results. Some of them even suggested that metformin may reduce the risk of cancer by as much as 50 percent.

Michael Pollak, M.D., a professor in the Departments of Medicine and Oncology at McGill University, and colleagues wanted to find out how this anti-diabetic drug reduced cancer risk. They wanted to pinpoint mechanisms that lead to this protective effect.

"It is remarkable that metformin, an inexpensive, off-patent, safe and widely used drug, has several biological actions that may result in reduced cancer risk," says Dr. Pollak. "These latest findings suggest that it reduces mutation rate in somatic cells, providing an additional mechanism by which it could prevent cancer."

Cell mutation and DNA damage are key parts in the development of cancer, but researchers have never been able to show that blocking these mutations could lower the risk of cancer.

The findings made by Dr. Pollack and his team show that metformin reduces levels of reactive oxygen species (ROS), substances that damage DNA. This process seems to happen in mitochondria, the parts of cells that make energy by burning nutrients.

In the past, studies have shown that metformin's anti-diabetic function also happens in the mitochondria. However, the researchers in these studies did not think the drug also minimized DNA damage in the same place.

"This study opens an exciting new direction in cancer-prevention research," says Dr. Pollack.

He is careful to point out that his team's findings do not suggest that metformin is ready to be used to prevent cancer. They still do not know if the usual doses used to treat diabetes are enough to reduce the risk of cancer. He also explains that they do not know "if the findings from the original studies showing reduced cancer risk, which were carried out in diabetics, also apply to people without diabetes." However, the researchers did not expect to find that such a safe and commonly used drug would protect DNA from getting damaged.

"This topic now needs further study at many levels," Dr. Pollack concludes.

The full results of this study are published in the journal Cancer Prevention Research

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Review Date: 
January 18, 2012
Last Updated:
January 18, 2012