Wednesday, June 27, 2012
In the largest study of genes and smoking performed in a minority population to date, researchers have discovered a gene variant that increases a person’s risk of smoking.
A study led by Memorial Sloan Kettering epidemiologist Helena Furberg has identified a genetic link to smoking addiction among people of African American descent. Published in the journal Translational Psychiatry in May, the findings could promote the development of more-effective therapies to help people quit smoking.
“Our research shows that willpower is not the only factor that influences how much a person smokes,” Dr. Furberg says. “Genes play a role as well.”
The researchers discovered a gene variant that is linked to how much an individual smokes. It occurs in a gene called CHRNA5, which is found on chromosome 15.
“What’s striking is that our earlier studies have identified the same gene to be associated with how much individuals of European descent smoke,” says Dr. Furberg. “But until now, it was unclear whether the genetic associations regarding smoking addiction would be the same for people of African descent.”
“Our new findings suggest that this gene is important for smoking addiction in all people, regardless of their ancestry,” she adds.
However, carrying this genetic variant imparts only a small risk of smoking more cigarettes. Additional factors influence smoking addiction as well. Dr. Furberg explains that getting tested for the variant, which only accounts for a difference of one cigarette a day, will not provide valuable information at this time.
“All smokers, whether they carry this variant or not, should be encouraged to quit,” she says.
Matching Smoking Habits with Genetic Variations
The study, which involved researchers at several institutions, is the largest of its kind carried out in a minority population, though similar investigations had previously been conducted in individuals of European descent. “Because smoking behavior is known to vary among racial or ethnic groups, it is important to perform these types of analyses in people of different backgrounds,” explains Dr. Furberg.
The researchers examined the genetic makeup and smoking behavior of 35,000 individuals of African descent. For all participants, they collected information on one million commonly occurring variations in the DNA sequence, as well as on four aspects of smoking behavior: whether the individuals have ever smoked, the age at which they started smoking, how many cigarettes they smoke, or smoked, per day, and whether they were able to quit.
Matching the data, they found that on average, people who have a single-letter variation in their DNA located within the CHRNA5 gene tend to smoke more than those individuals who do not carry the variant. This gene produces a protein called nicotine acetylcholine receptor, which is known to play a role in nicotine addiction. Dr. Furberg notes that it is not yet known why people who carry the genetic variant tend to be more addicted to smoking, though it is likely that the variant makes the brain more responsive to nicotine. She and her colleagues are hopeful that their findings will inspire more research to shed light on the biology of smoking addiction.
In the future, such research could result in better therapeutic approaches to help individuals quit smoking. For example, genetic information could be used to determine a person’s addiction level and what types of nicotine replacement therapy he or she might benefit from.
“Because smoking is a leading cause of cancer, heart disease, and other illnesses, more-effective ways to help people quit could potentially be of huge benefit for human health,” Dr. Furberg adds.
This research was supported by the National Cancer Institute of the National Institutes of Health under award number CA118412.