Female smokers who have a slower-acting version of a gene involved in breaking down tobacco-related carcinogens are at increased risk of developing breast cancer, according to researchers.

Science Daily reported Feb. 9 that a study of pre- and post-menopausal found that smokers with a version of the NAT2 gene that produces a slower-acting version of the enzyme N-acetyltransferase 2 -- which helps break down carcinogenic aromatic amines -- were more likely to develop breast cancer. Those who smoked the most and had the slowest-acting version of the enzyme were at the highest risk.

"These results, analyzing all studies to date, indicate that subgroups of women defined by genetic predisposition are at higher risk of breast cancer if they are exposed to tobacco smoke," said lead researcher Christine Ambrosone, Ph.D., of the Cancer Prevention and Population Sciences Program at Roswell Park Cancer Institute. "In fact, smoking is likely to play an important role in the development of breast cancer for about 50-60 percent of the populations from European descent who have a form of the NAT2 gene that gets rid of aromatic amines more slowly than the rest of the population."

The study was published in the Jan. 1, 2008 issue of the journal Cancer Epidemiology, Biomarkers and Prevention.