The incidence of breast cancer is lower among African-American women than women of other ethnicities. However, the breast cancers these women develop are often more invasive and aggressive. Assistant Professor Theresa Swift-Scanlan is investigating the reasons behind this disparity and believes the answer partly lies in understanding epigenetic modifications to women’s DNA and how they are
affected by lifestyle behaviors and environmental exposures. Epigenetic modifications are molecular level changes that alter gene expression without altering the primary sequence of DNA.
According to Swift-Scanlan, African-American, pre-menopausal women are more likely than women of other ethnicities to develop basal-like breast cancer, a tumor subtype that does not have receptors for estrogen or the growth factor HER2. Basal-like tumors are resistant to effective therapies that target these receptors, such as tamoxifen and herceptin. The end result is that the tumors are very difficult to treat and are associated with increased morbidity and mortality.
According to previous research, Swift-Scanlan said, while basal-like tumors occur in white women and other ethnic groups at all ages, it is at a lower frequency than in African-American, pre-menopausal women. Differences in the frequency of this tumor subtype appear to be influenced by varying distributions of risk factors across ethnic groups. The number of children breastfed and the increased duration of breastfeeding decreases the risk of basal-like breast cancer. Unlike other breast cancer subtypes, having more children at a younger age appears to increase rather than decrease risk for basal-like breast cancer.
The Susan G. Komen Foundation awarded Swift-Scanlan a three-year, $450,000 Career Catalyst in Cancer Disparities Award to study gene methylation in basal-like breast cancer and four other tumor subtypes. The grant funds her efforts to determine whether DNA methylation — which can silence genes by changing the way the DNA is packaged within the cell — in concert with known breast cancer subtype risk factors, could unearth ways to reduce mortality from the disease among African-American women. She also has funding through a National Institutes of Health Career Development Award.
Swift-Scanlan hopes to identify genes that, when methylated, could contribute to early disease detection and risk assessment for all women.
“I hope that this research will help women in the decision making process,” she said. “Deciding what to do after a breast cancer diagnosis is a very personal and profound choice. Having this knowledge could help providers assist women in making the best decision for them while avoiding the problem of over- or under-treating the disease.”
Swift-Scanlan will analyze breast tissue samples and clinical data from at least 160 African-American women enrolled in the Carolina Breast Cancer Study, 80 of whom are pre-menopausal and 80 who are post-menopausal. Her main collaborators are genetics Associate Professor Charles Perou at the Lineberger Comprehensive Cancer Center and epidemiology Professor Robert Millikan at the School of Public Health.