The high rates of type 2 diabetes in some minority communities as well as the rates for prostate cancer among African American men are a good illustration of how a person’s risk for a disease can depend on ancestry.
The problem is scientists haven’t done enough research in minority communities to be able to learn just how much of a role ancestry plays in the development of those and other diseases. While some of the differences in risk may be due to environment and lifestyle, it’s a good bet that genetics also plays a role.
A recent study highlights why it’s so important to conduct ancestry-specific research, and why research findings are difficult to apply across different ethnicities. In this case, scientists were investigating the genetic influences of breast cancer in African-American women.
Most of the genetic factors linked to breast cancer were discovered among women of European and Asian ancestry. But African American women not only have higher rates of breast cancer, but they are 40 percent more likely to die from the disease than women of European ancestry. African-American women also tend to be diagnosed at a younger age and are more likely to experience the more aggressive types of the disease. While there may be many factors involved in these differences, including access to early screening and quality care, understanding the role genetics may play in these differences is also important.
The study, titled “Evaluating Genome-Wide Association Study-Identified Breast Cancer Risk Variants in African-American Women” and published by the peer-reviewed journal PLOS One, claims to be the first to examine all the known breast cancer genetic markers in African-American women. The international team of scientists looked at 67 genetic variants associated with breast cancer in women of Asian and European ancestry. This is the first study to investigate how relevant these variants are in African-American women, say the researchers. To find out, they tested the DNA of about 1200 African-American women diagnosed with breast cancer and 2,000 African-American women who served as a control group.
What researchers found was that only about 10 percent of the genetic markers associated with breast cancer in women of Asian and European ancestry were found to have significant associations with breast cancer in African American women. In that group of genetic markers associated with breast cancer among African American women, researchers found one that is linked to one of the more aggressive types of breast cancer — known as estrogen receptor (ER)-negative breast cancer. This type of breast cancer is also much more prevalent among African American women.
The findings also mean, of course, that 90 percent of the markers associated with breast cancer in European-and Asian-American women aren’t necessarily linked to the disease in African-American women. This conclusion is consistent with results from previous studies.
But the new study underscores the complexity of applying previous research to a specific population, and the need for more large-scale studies on African-American women.