Diabetes drug fights lung cancer in mice: Study

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WASHINGTON: A popular drug that is used by millions of diabetics around the world significantly decreases tobacco-induced lung tumors in mice, a study published Wednesday found.

Researchers led by Philip Dennis, a senior investigator at the National Cancer Institute (NCI), gave the diabetes drug metformin to mice which had been exposed to a carcinogen derived from nicotine.

Mice treated orally with the diabetes drug had 40-50 percent fewer lung tumors than untreated mice, while those treated by injection had nearly three-quarters fewer tumors, the study published in Cancer Prevention Research said.

Based on the findings in mice, the researchers are considering holding clinical trials of metformin to determine if it could be used to prevent lung cancer in smokers.

"Although smoking cessation is the most important step for current smokers, over half of lung cancer cases are diagnosed in former smokers, raising the importance of identifying those at highest risk and identifying effective preventive treatments," Dennis said.

Earlier studies have shown that diabetics who take metformin have a lower risk of developing cancer.

In the study published Wednesday, the researchers "controlled for glucose levels, which suggest that the effect may be seen beyond the diabetic population," said Jeffrey Engleman, director of the centers for thoracic cancers at Massachusetts General Hospital.

The study showed that metformin activates an enzyme that neutralizes a protein which plays a key role in the growth and survival of cancerous cells in the lung, said Dennis.

Dr Michael Pollak, professor of medicine and oncology at McGill University said the "important laboratory study, together with prior laboratory and epidemiology research, suggest that metformin may be useful in cancer prevention and treatment.

"There is new information available about the mechanisms by which this drug, which is based on compounds present in lilac, may be useful for cancer control," Pollak said.

Studies conducted in Britain in 2005 showed that diabetics who took metformin had a 40-percent lower risk of cancer compared with diabetics who did not take the drug, Pollak told a news conference.

Other laboratory studies have found that metformin can block the growth of many, but not all, cancer cells by targeting their energy intake, Pollak said.

Metformin was approved by the US drug safety regulator, the FDA, for the treatment of type two diabetes in 1995. As of 2008, 40 million people in the United States took metformin.

The deadliest of all cancers, lung cancer claims nearly eight million lives a year.

It is also the fastest-growing form of cancer with more than 12 million new cases diagnosed annually.