As a new year begins, cigarettes are no doubt the focus of countless resolutions. But the highly addictive nature of nicotine makes butting out hard to do. Now research published in the current issue of the Journal of Clinical Investigation provides further impetus for smokers to kick the habit. Although tar has long been considered the carcinogenic agent in cigarettes, the new findings further suggest that nicotine and compounds derived from it may also help promote the development and progression of cancer.

Phillip Dennis of the National Cancer Institute and his colleagues exposed normal human lung cells to concentrations of nicotine and its derivative NKK comparable to those supplied by cigarettes. Within minutes, the team found, the so-called Akt molecular pathway became active. This pathway fosters cell growth and survival and is thus antithetical to the body's major defense against cancerous tumors: apoptosis, or programmed cell death. The researchers also identified active Akt pathways in the lungs of mice treated with NKK and in the lung tissue of smokers. The authors conclude that although nicotine is not yet considered a carcinogen, their findings might have implications for smoking cessation methods because "the risks of long-term nicotine supplementation are unknown."