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.