Metformin, a drug commonly used to treat type 2 diabetes, shows potential in the prevention of tobacco-induced lung tumours and possibly colorectal tumours, according to two studies published in Cancer Prevention Research.

The first study, conducted by researchers at the NCI, showed that metformin significantly decreased lung tumour burden in mice exposed to a nicotine-derived nitrosamine called NNK, which is the most prevalent carcinogen in tobacco. Researchers treated the mice with metformin either orally or by injection. Those treated orally had between 40 and 50 percent fewer tumours, while those mice treated with injection had 72 percent fewer tumours. Based on these findings, clinical trials of metformin are being considered to determine if this compound could be used as an effective chemoprevention agent for smokers at high risk of developing lung cancer.

A second study, conducted by researchers in Japan, showed, non-diabetics taking metformin had a significantly lower rate of rectal aberrant crypt foci, a surrogate marker of colorectal cancer. Patients in the treatment group had a mean of 5.11 foci compared with 7.56 in the control group.

Results of these studies were discussed at a teleconference hosted by Dr Scott Lippman, professor and chair in the department of thoracic head and neck medical oncology at the University of Texas M. D. Anderson Cancer Center on Wednesday.

Metformin significantly decreased lung tumour burden in mice exposed to a nicotine-derived nitrosamine called NNK, which is the most prevalent carcinogen in tobacco. Metformin has been previously shown to activate an enzyme called AMP-activated protein kinase that is known to inhibit mTOR, a protein that regulates cell growth and survival in tobacco carcinogen-induced lung tumours.

Source: Association for Cancer Research