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Gene may determine success of smoking cessation

DANA POINT, California (CNN) -- Genes rather than willpower may predetermine if a person can successfully quit smoking.

Scientists have shown for the first time that a gene known to be associated with drug and alcohol addiction also plays a role in the outcome of smoking cessation attempts.

Scientists at the M.D. Anderson Cancer Center in Houston, Texas, wanted to know if there was a genetic difference between people who successfully quit smoking and those who failed.

In the past, researchers have compared smokers to non-smokers to identify genetic differences. Knowing how genetics influence smokers could lead to better treatment programs.

In the new study, 134 people were chosen participate in a smoking cessation program. All carried a specific gene called DRD2, which is a dopamine receptor. Dopamine is a neurotransmitter that influences how brain cells communicate with each other.

All were given counseling and a nicotine patch, and were randomly selected to receive an antidepressant drug or a placebo.

Researchers found that among those smokers taking the placebo, 25 percent abstained from cigarettes for 18 weeks, compared with 37 percent for those taking the antidepressant.

They also found that those participants with a certain type of the DRD2 gene were more likely to start smoking again after the 18 weeks -- they surmised that it might also determine the effectiveness of the antidepressant in smoking cessation.

The DRD2 gene is made up of a pair of alleles. These alleles "come in two forms -- either A1 or A2 -- you get one from your father and one from your mother," said Paul Cinciripini, director of the Tobacco Research and Treatment Center at M.D. Anderson and one of the study's authors. "If you have the A1 allele, you quit (smoking) less often."

The participants who had the A2 allele had a good response to the antidepressant.

DRD2 is the most widely studied dopamine gene, according to Cinciripini. It has been found in people with obesity, alcoholism, cocaine addiction and pathological gambling.

This is the first study to look at how genes can contribute to or hamper smoking cessation efforts. The research was presented at a conference in Dana Point, California, sponsored by the American Cancer Society.

"If we genetically characterize the dependent smoker we can potentially tailor-make drugs for each genetic profile or to simplify, if you have genetic profile x, y and z, you can find different drugs that work for x, y and z," said Dr. Dileep Bal, president of the American Cancer Society.

The importance of this work is "not to preordain or predetermine what's going to happen to people, but it's to identify the areas to provide a little extra assistance to people trying to quit," added Dr. David Burns, professor of Medicine at the University of California at San Diego.

Cinciripini said he could envision that in the future, smokers may be screened for this particular gene, so that they may receive specific drugs that may help them successfully stop smoking.

Smoking rates are slowly declining in the United States according to the American Cancer Society, but they continue to rise in developing countries. The World Health Organization estimates that, based on current smoking patterns, smoking will eventually kill 500 million people worldwide.



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RELATED SITES:
American Cancer Society
M. D. Anderson Cancer Center
World Health Organization

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