Metformin may have the following brand names: Fortamet, Glucophage, Glucophage XR, Glumetza, or Riomet.
mTOR is a protein that helps tobacco-induced lung cancer tumors grow. Studies have shown that metformin switches on an enzyme that blocks mTOR.
Study 1 - carried out by scientists at the National Cancer Institute (NCI), and led by Dr. Philip Dennis, revealed a significantly lower lung cancer tumor burden in mice that were given metformin and were exposed to NKK, a nicotine-derived nitrosamine - the most prevalent tobacco carcinogen. The mice were treated with metformin either by injection or orally (by mouth). Those receiving the medication by mouth had 40% to 50% fewer tumors compared to mice that did not receive the drug. The mice injected with metformin had 72% fewer tumors, the investigators inform.
Dr. Dennis said:
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.
The authors write that clinical trials are being considered to find out whether metformin might be used as an effective chemoprevention agent for smokers. The majority of lung cancer patients became ill because of regular smoking. (Clinical trials involve human beings, rather than animals)
Study 2 - investigators in Japan demonstrated that individuals without diabetes who took metformin had a considerably reduced rate of rectal aberrant crypt foci, a surrogate marker of colorectal cancer. Trial participants who received metformin had a mean of 5.11 foci versus 7.56 among those who took a placebo (control group).
You can listen to a teleconference (link below) hosted by Scott Lippman M.D., editor-in-chief of Cancer Prevention Research. Lippman is professor and chair in the department of thoracic head and neck medical oncology at the University of Texas M. D. Anderson Cancer Center.
Download the mp3 of the teleconference (10.7 MB, 46 minutes and 51 seconds)
"Metformin Prevents Tobacco Carcinogen-Induced Lung Tumorigenesis"
Regan M. Memmott, Jose R. Mercado, Colleen R. Maier, Shigeru Kawabata, Stephen D. Fox, Phillip A. Dennis
Cancer Prevention Research September 2010 3; 1066
"Metformin Suppresses Colorectal Aberrant Crypt Foci in a Short-term Clinical Trial"
Kunihiro Hosono, Hiroki Endo, Hirokazu Takahashi, Michiko Sugiyama, Eiji Sakai, Takashi Uchiyama, Kaori Suzuki, Hiroshi Iida, Yasunari Sakamoto, Kyoko Yoneda, Tomoko Koide, Chikako Tokoro, Yasunobu Abe, Masahiko Inamori, Hitoshi Nakagama, Atsushi Nakajima
Cancer Prevention Research September 2010 3; 1077