Smoking Increases Breast Cancer Risk Based On Genes, Study Shows

A research group led by Christine Ambrosone, PhD, Cancer Prevention and Population Sciences Program, Roswell Park Cancer Institute (RPCI) and Jenny Chang-Claude, PhD, Professor in Epidemiology at University of Heidelberg analyzed data from 10 of the 13 studies published in the last 10 years in which they evaluated genetic information, smoking habits and breast cancer risk in 4,889 premenopausal and 7,033 postmenopausal women.

Analysis demonstrated a significant interaction between breast cancer risk, smoking, and a specific gene called the NAT2 that produces the enzyme, N-acetyltransferase 2 (NAT2). This enzyme helps break down aromatic amines − a major class of tobacco smoke carcinogens – that are then excreted from the body. Individuals have either rapid or slow activity based upon their genotypes; people with the slower enzyme are unable to rid the body of aromatic amines as efficiently as those who have the faster enzyme.

As a result, the likelihood of DNA damage is greater as is the subsequent development of breast cancer. The results of this study demonstrated that women who smoked the most years, consumed the highest number of cigarettes per day and had NAT2 slow genotypes were at significantly increased risk of breast cancer. The group also performed a meta-analysis of all published studies and found similar associations.

“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 Dr. Ambrosone. “In fact, smoking is likely to play an important role in the development of breast cancer for about 50-60% 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.”