"Variations in the region of chromosome 15 were more common in cases of lung cancer than controls, far above what we would have expected by chance," Brennan said during the teleconference. "There was about a 30 percent increased risk for those who have one variant and about an 80 percent increased risk for lung cancer for those with two variants."
These variants are in genes that affect nicotine addiction, but they are also involved in making cells increase in number, which may increase the chances of development of a tumor, Brennan said.
While the association between nicotine addiction and increased smoking and lung cancer seemed a likely explanation, Brennan's team rejected this hypothesis. "We tended to conclude that the association was primarily not due to tobacco addiction," he said.
Brennan's team found that how much one smoked or for how long had no effect on the risk for lung cancer. In addition, the gene variants were found among people who never smoked.
The researchers also looked at people who had other diseases associated with smoking but could not find an association between a gene variant and these diseases, Brennan said. "These gene variants appear to be specific for lung cancer and not other diseases strongly associated with tobacco," he said.
In the third study, from Nature Genetics, Dr. Christopher Amos of the M.D. Anderson Cancer Center in Houston and his colleagues analyzed about 3,000 patients with lung cancer who had been smokers.
As in the other studies, Amos said his group also found a 30 percent increased risk among individuals with one variant and about 80 percent increased risk for lung cancer among the 10 percent of the population that had two copies of the variant.
"What is remarkable about our studies is how similar the results are with respect to lung cancer risk," Amos said during the teleconference.
Amos's team did find an
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