A common treatment for patients with type 2 diabetes could one day help smokers avoid lung cancer, say scientists at the National Cancer Institute.
Metformin decreases levels of insulin-like growth factor-1 (IGF-1) and circulating insulin, which is important in patients with type 2 diabetes. Early laboratory research presented at the American Association For Cancer Research's annual meeting shows that the drug may also inhibit tumor growth as well.
"This well tolerated, FDA-approved diabetes drug was able to prevent tobacco-carcinogen induced lung tumors," said Phillip A. Dennis, M.D., Ph.D., senior investigator in the medical oncology branch of the National Cancer Institute.
Researchers treated mice with metformin for 13 weeks following exposure to a nicotine-derived nitrosamine (NNK), which is the most prevalent carcinogen in tobacco and a known promoter of lung tumorigenesis.
When given orally, metformin was well tolerated and reduced tumor burden by 40 percent to 50 percent. The levels of metformin reached in mice are readily achievable in humans.
Scientists further evaluated the effects of metformin on a series of biomarkers for lung tumorigenesis and found that it inhibited mammalian target of rapamycin (mTOR), which promotes lung tumor growth, by decreasing levels of circulating insulin and IGF-1. This effect was even more profound when metformin was administered to mice by injection, which reduced lung tumor burden by 72 percent.
Citation: Memmott et al., 'Metformin, an antidiabetic drug that modulates the AMPK/mTOR pathway, prevents tobacco carcinogen-induced lung tumorigenesis', AACR Annual Meeting, April 2010; abstract # 2928
