After disturbing warnings about negative side effects of common diabetes drugs, it was refreshing to read about a positive side effect of one of the most-prescribed diabetes drugs. Researchers at the University of Pennsylvania School of Medicine have found that metformin (sold as a generic and under the brand name Glucophage) has the unique benefit of killing certain cancer tumor cells.

While there are certainly no guarantees that taking metformin means you’ll never suffer from cancer, the results of this research were truly remarkable.

The most common mutation in cancer cells is a missing gene named p53, which controls cell division and metabolism. In fact, half of all cancer tumors are missing the p53 gene. Researchers have struggled for years to address this mutation because today’s most advanced medications are designed to interact with a specific gene or gene function. But when the problem is a missing gene, the challenge becomes much more difficult.

That’s where metformin comes in. One of the functions of metformin is to force cells to switch their metabolic pathway. Because a cell’s metabolic pathways are controlled by p53, the cancer cells are unable to switch. The result is that the cancer cells shrink and die.

Two previous observational studies found that diabetics who take metformin are less likely to be diagnosed with cancer and less likely to die from cancer. This latest research demonstrated why by showing the cancer-fighting effects in laboratory mice. Further clinical trials are needed before metformin will actually be used as an anti-cancer medication. However, for many diabetics, this is a welcome bit of good news about a medication.