Women are at much greater risk of smoking-related lung cancer than men because of their genetic make-up, according to new US research.
Scientists at the University of Pittsburgh have discovered that a gene that promotes lung-cancer growth is more active in women than in men. They also found that nicotine in cigarettes promotes this gene's activity.
The research is published today in the Journal of the National Cancer Institute, and provides the first biological explanation for the greatly increased lung-cancer risk women smokers face compared with men.
"Our research strongly suggests that women are likely to develop lung cancer after much less smoking exposure than men and much earlier in life, regardless of their smoking history," said Dr Sharon Shriver, principal investigator on the study. The research was "the first study to provide a mechanism for cancer promotion in this population", she added.
The team found a gene on the surface of cells lining the lung which when stimulated could trigger the out-of-control cell growth typical of lung cancer. They looked at lung tissue samples from 38 women and 40 men, including 58 patients with lung cancer, and found that 55 per cent of the women non-smokers and 75 per cent of the women smokers showed activity in the critical gene. By contrast, none of the male non-smokers and only 20 per cent of the male smokers showed this gene activity.
The gene is positioned on the X chromosome, the researchers said. Women have two X chromosomes, while men have only one. Normally in a woman duplicate genes are inactivated on one of the X chromosomes, but both copies of this lung tissue gene are active.
This might be a reason women smokers were at greater risk of lung cancer, Dr Shriver said. The gene might also be naturally more active in women than in men. "The take-home message, especially for teenage girls, is that they should stop smoking or, better yet, never start," she added.
"Prior reports have suggested various molecular markers associated with an increased risk in women smokers. However, ours is the first study to provide a mechanism for cancer promotion in this population," said Prof Jill Siegfried, senior author of the report and co-director of the University of Pittsburgh Cancer Institute's Lung Cancer Centre.
"This study also validates previous population studies suggesting that women are at substantially increased risk of smoking-related lung cancer."
