Two New Mutations Linked to Breast Cancer in Black South African Women

A study of nearly 2,500 Black South African women diagnosed with breast cancer has identified two new genetic mutations linked to the disease. The mutations could be targets for new medicines, as well as pave the way for the development of more accurate breast cancer risk calculators.

The research was a genome-wide association study, which analyzes all the DNA of many people to find genetic differences linked to a specific disease or trait.

About 10% of breast cancers are thought to be hereditary, meaning they’re linked to genetic mutations passed from parent to child. In women of European descent, mutations in the BRCA genes are the most common mutations linked to breast cancer. But until this study, little research had been done on genetic changes linked to breast cancer in African women.

The researchers analyzed the DNA of more than 3,500 Black South African women — including 1,000 who didn’t have breast cancer. The researchers found that people who had mutations in the USP22 and RAB27A genes were more likely to have breast cancer than those who didn’t have these mutations.

“These genes have not been associated with the disease before, which is an important advance in understanding breast cancer risk and biology in women of African ancestry,” lead author Mahtaab Hayat, PhD, said in a statement. Hayat is a lecturer at the University of the Witwatersrand.

According to the researchers, most genome-wide association studies of breast cancer have included only non-African populations, with almost 80% of all these types of studies done in people of European ancestry. Studies of breast cancer genetics in African people have mainly focused on African-American women, who are largely of West African ancestry.

This is likely why many current breast cancer risk calculators aren’t as accurate for women who aren’t of European ancestry. After a calculator is developed, scientists test its accuracy against information from hundreds of thousands of women who have and haven’t been diagnosed with breast cancer. Most calculators available today were created based on data from women with European heritage. The researchers hope these new findings will allow scientists to create risk calculators that are more accurate for African women.

The researchers plan to confirm the results of their research in future studies and hope that the mutations could be targets for new breast cancer medicines, much like PARP inhibitors target breast cancers with a BRCA mutation.