Journal of the National Cancer Institute paper states that variant conferred more risk in those with low smoke exposure.
A team of scientists have discovered a gene variant that increases the risk for both nicotine dependence and lung carcinogenesis. It does not, however, affect risk for developing other smoking-related cancers or for lung cancer in people who never smoked, they add.
Three recent studies associated a region of chromosome 15 with lung cancer risk. Though two resident genes encode subunits of the nicotine receptor, it has not been clear if the source increases the risk of lung cancer by increasing the risk of smoking, if it has a direct impact on the development of lung carcinogenesis, or if it affects both causal pathways.
To distinguish between those mechanisms, the researchers reanalyzed their genome association data in 3,621 patients and control subjects, looking for association between the previously-identified variant on chromosome 15 and smoking behavior. They also looked for an association between the variant and bladder cancer in 1,092 bladder cancer patients and control subjects and between the variant and kidney cancer in 285 kidney cancer patients and control subjects.
The investigators found a statistically significant association between the variant and some smoking behaviors that are an indication of physiological nicotine dependence, such as the time an individual waits before having their first cigarette in the morning.
The group also found that the variant had a larger impact on lung cancer risk in individuals who had low smoke exposure compared with those who had a high lifetime exposure, suggesting that the variant has a direct impact on lung cancer development.
The variant was not associated with an increased risk of lung cancer in people who had never smoked. They also did not find an association between the variant and bladder or kidney cancer risk.
Researchers at the University of Texas M.D. Anderson Cancer Center and two other groups worked on the study, which appears in the Journal of the National Cancer Institute.
