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Smoking Guns: DNA Repair and Lighting Up
By Kate Dalke

An x-ray of a chest showing cancer in the lungs. People who can't repair their DNA normally are at greater risk for the disease.

No one should smoke, but some people really shouldn’t smoke.

Scientists have found that smokers who do not repair mistakes in their DNA normally are 100 times more likely to develop lung cancer than non-smokers.

Doctors could one day use the research to identify smokers most at risk for developing lung cancer as they try to persuade them to quit.

For now, the study is another step toward understanding the complex pathways involved in DNA repair and cancer. For years, scientists have been developing ways to measure the effects of DNA repair on disease.

In the new study, scientists measured the activity of an enzyme involved in DNA repair among 68 smokers and 68 non-smokers. The enzyme, called OGG, is just one of many—perhaps hundreds—that play a role in DNA repair.

The researchers found that, in general, the activity of this particular enzyme is the same for everyone—smokers and non-smokers, young and old people, and men and women.

The danger comes when a person has two independent risk factors: smoking and reduced DNA repair activity.

Our bodies repair DNA constantly as cells reproduce. But carcinogens in tobacco increase the DNA damage to lung cells. Those smokers who repair their DNA less efficiently than others are more likely to develop lesions and cancer.

Of course, most tobacco users know about the health risks of smoking and chewing. Will testing and informing people that they are more at risk make a difference?

Yes, says Zvi Livneh of the Weizmann Institute of Science in Israel, where the study was done. “Screening for smokers with low OGG activity, followed by smoking cessation in these individuals, may lead to a decrease in the incidence of lung cancer,” the researchers write in the Journal of the National Cancer Institute.

Extending the study to include more factors such as the differences between heavy and light smokers, medication and environment will be important, according to Neil Caporaso of the National Cancer Institute in Bethesda, Maryland, who wrote an accompanying commentary.

—Related Article—

Melanoma linked to problems with repairing DNA

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Paz-Elizur, T. et al. DNA repair activity for oxidative damage and risk of lung cancer. Journal of the National Cancer Institute 95, 1312-1319 (September 3, 2003).
Caporaso, Neil. The molecular epidemiology of oxidative damage to DNA and cancer. Journal of the National Cancer Institute 95, 1263-1265 (September 3, 2003).

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