Ex-smokers at 'lung cancer risk'
Updated on 29 August 2007
Smoking can permanently alter the activity of genes and have irreversible effects on DNA that may be linked to cancer, new research has shown.
The findings may help to explain why some former smokers contract lung cancer long after they have quit.
Scientists carried out a detailed study of cell samples from the lungs of eight current smokers, 12 former smokers and four people who had never smoked.
Libraries of DNA sequences were constructed containing data on the activity of more than 1,700 genes.
The Canadian team found some changes in gene activity, or expression, that affected current smokers but reversed after they had quit the habit for a year or longer.
But others appeared to be permanent, including a number that were likely to increase cancer susceptibility. A third group were only partly reversible.
In particular three genes associated with DNA repair had reduced activity levels in smokers which did not return to normal after they gave up the habit.
One, APEX1, had been shown to harbour DNA variants linked to lung cancer susceptibility. The others were REV1L and the tumour-suppresser TUSC4.
Irreversibly reduced expression of another gene, GSK3B, in smokers could account for an exaggerated inflammatory response and contribute to the development of lung cancer, said the scientists.
Two more genes both associated with mucus secretion in the lungs showed smoking-related over-activity that might also play a direct or indirect role in cancer.
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