Breast Feeding May Heal DNA Damaged from Environmental Pollutants

Amanda Mitchell for TEI - 5/18/07

In 2007, the American Cancer Society estimates that more than 180,000 new cases of breast cancer will be diagnosed this year. To date, it is the second most deadly cancer in women, next to lung cancer.

Fortunately, breast cancer research is nearly as prolific as the cancer itself.  Dr. Kathleen Arcaro, Assistant Professor of Environmental Toxicology at the University of Massachusetts Amherst has recently received $100,000 in funding from Avon to study the correlation between breast cancer risk and early pregnancy by examining the cells in breast milk.

The grant comes after preliminary studies completed by Arcaro and her team suggested that breast feeding reduces the amount of environmental toxicants in the breast. The study consisted of 21 women from the Springfield, Massachusetts and Albany, New York areas. Arcaro and her team studied the breast milk from each of these women in search of trace amounts of pesticides and compounds once used as plasticizers such as polychlorinated biphenyls (PCBs). They also examined the DNA damage in the naturally exfoliated cells present in the milk.  

At the time of the preliminary study, no other research had yet been completed to correlate the environmental pollutant levels in milk with the DNA damage in cells obtained from the milk. Arcaro believes that increased genetic instability, resulting from exposure to environmental toxicants may increase an individual’s risk of developing breast cancer. Her goal is to determine the extent to which environmental pollutants result in an increase in genetic instability.

The results of the preliminary study were promising for Arcaro. The women involved ranged from 21 and 40 years in age, and their children from 3.5 weeks to 67 weeks in age. Testing revealed that all 21 of the women’s milk samples were tainted with pesticides and PCBs . However, among the 15 women who had not previously nursed a child, the age of the individual and the level of toxicants in the milk showed a direct relationship. The samples of the 6 women who had previously nursed another child did not show such a relationship, suggesting that breastfeeding helped rid  the breasts of the environmental toxicant s present in the other women.  However, the study did not reveal a direct relationship between the level of pollutants in the milk and the level of DNA damage in the cells in the milk.

Arcaro reports that her first study did not attempt to differentiate cell type in the milk. Because DNA damage and repair is thought to differ among cell types, it is possible that different cell types within the milk samples examined may have obscured the correlation between DNA damage and environmental pollutants . As a result, she worked to isolate the viable mammary epithelial cells from the other cells present in breast milk and plans to examine the DNA damage in the pure epithelial cell population in her next study.  

The grant from Avon will allow Arcaro and her colleagues to examine the related question of why women who give birth before they are 25 years old have a reduced lifetime risk of developing breast cancer.  In this study they will examine epigenetic changes (which are small changes made to DNA) that occur with time and age in all humans.  Arcaro and colleagues, Professors Douglas Anderton and Sallie Smith-Schneider, propose that early pregnancy and lactation re-set the epigenetic clock of breast epithelial cells reducing a woman’s risk of developing breast cancer.  During the next two years they will collect milk from 50 local women of any age who are nursing their first child and 50 women of any age who are nursing a child from at least their second full-term pregnancy and who had their first child before they were 25.   She predicts that pregnancy before the age of 25 and lactation will inhibit epigenetic changes in tumor-related genes.

Arcaro’s studies are attempting to explain why women who have had and nursed a child before the age of 25 have a decreased lifetime risk of developing breast cance . It is hoped that this knowledge can be used to develop preventive treatments for all women.  Her local study began in January, and will continue until 2009. She is still looking for women to participate in the study. Please call 413 577-1823 or send an email to karcaro@nre.umass.edu if you are interested in participating in this study.