Smoking and genetics
Posted: Wednesday, April 02, 2008 5:21 PM by Sam Singal
By Robert Bazell, NBC News chief science correspondent
My mother and her identical twin smoked enormous numbers of cigarettes from their teenage years until their deaths – my mother at age 90 and my aunt at 91. Neither developed lung cancer. But lest anyone think this is a recommendation for smoking, they both endured years of misery from emphysema and my mother (and probably my aunt) died from kidney cancer which is linked to smoking.
The point here is something that has long been known. While 80 to 90 percent of people who develop lung cancer are smokers or former smokers, only 15 percent of people who smoke significant amounts get the disease. The assumption has always been that genetics provided the explanation –and the case of the twins so important to my life provide a tiny piece of evidence.
But now the knowledge from the human genome project is starting to provide specific information that fills in the blanks. Three large groups of researchers found an area of genetic variability on chromosome 15 that increases the risk of lung cancer in smokers. While the three groups worked independently they came to remarkably similar conclusions. You can read the original research here AND here AND here.
The gene alterations described by these scientists are responsible for proteins in the lungs that act as receptors or binding sites for nicotine. That means they probably enhance the effects of nicotine on those with this genetic makeup—making it harder to stop smoking. They also seem to facilitate the passage of poisonous substances from nicotine into the lungs, accelerating the chain of events in the lung cells that leads to cancer.
Like most exciting, but basic research this has no immediate application. But it there is a good chance that this could lead to a blood test to determine who which smokers or former smokers are most at risk for lung cancer. Those would the ones who should get a screening test such as a spiral CT scan to find early stage lung cancer. (GE, parent company of NBC, makes many of the machines used for spiral CT scans).
The new genetic knowledge could also lead to better drugs to block the effects of nicotine and better help smokers to quit.
It is important to note that two of the three research groups looked at non-smokers who had the genetic variation. Those people were not at risk for lung cancer. It is the tobacco with its nicotine which is villain here – not anyone’s genetics.
