Source: Seattle Times (WA) Copyright: 1999 The Seattle Times Company Website: http://www.seattletimes.com/ Contact: 25 Jan 1999 Author: Malcolm Ritter, The Associated Press STUDY: GENE MAY AFFECT VULNERABILITY TO SMOKING Scientists have identified another gene that might affect how vulnerable a person is to cigarette addiction. The finding may help researchers develop new ways to stop smoking. Having a certain form of the gene makes it easier to kick the habit, or perhaps to avoid getting hooked in the first place, two studies suggest. But that apparent influence is modest. "This is just one small piece of the puzzle" of what influences smoking behavior, said psychologist Caryn Lerman, an author of one of the studies. Lerman is director of cancer genetics at the Lombardi Cancer Center of Georgetown University Medical Center in Washington. Her work and a follow-up study by Dr. Dean Hamer of the National Cancer Institute and colleagues appear in this month's issue of the journal Health Psychology. It's at least the third gene to show evidence of an effect on smoking. Scientists hope that by understanding such influences, they can tailor treatments to particular smokers and get hints for finding better therapies. Ken Kidd, a Yale University geneticist who has studied the genetic marker used by the researchers, criticized the design of the studies and analysis of the results. "I do not accept their conclusions," he said. Nicotine causes a surge of a substance called dopamine between certain brain cells. That feels good to the brain, so it encourages addiction. Brain cells use squirts of dopamine to communicate, and the gene in the new research tells brain cells how to make a structure called a transporter that mops the chemical up. Why would one version of this gene discourage nicotine addiction? Lerman and colleagues theorize that it leads to a less efficient dopamine transporter, which leaves more dopamine between the brain cells. That might reduce a person's desire to pump up dopamine levels by using nicotine, they suggest. Hamer's team found that people with the apparently protective version of the gene scored lower than other people on novelty-seeking, a personality trait that includes impulsiveness and an interest in experiencing new sensations. Novelty-seeking might promote cigarette addiction, so scoring lower on this trait might also be protective, they said. Lerman and colleagues studied 289 smokers and 233 people considered nonsmokers because they had smoked fewer than 100 cigarettes in their lifetimes. The apparently protective version of the transporter gene appeared in 56 percent of nonsmokers vs. just 47 percent of smokers. That suggests it helped people avoid getting hooked. - --- MAP posted-by: Mike Gogulski