Good news for Latinas: Researchers have found a gene variant common in women with Latin American ancestry that safeguards them against breast cancer. It doesn’t mean that Latinas can’t get the disease, but it does explain why far fewer of them develop breast cancer compared to women of other ethnicities.
The tiny gene variant, which is called a single-nucleotide polymorphism (SNP), gives Latinas protection from more aggressive estrogen receptor–negative types of breast cancer — the kinds that are linked to poor long-term survival. The new study was published in Nature Communications.
"The effect is quite significant," Dr. Elad Ziv, a professor of medicine at the University of California, San Francisco (UCSF), and senior author of the study, said in a press statement. "If you have one copy of this variant, which is the case for approximately 20 percent of U.S. Latinas, you are about 40 percent less likely to have breast cancer. If you have two copies, which occurs in approximately 1 percent of the U.S. Latina population, the reduction in risk is on the order of 80 percent."
Women with the gene variant have breast tissue that appears less dense on mammograms. High "mammographic density," or dense breast tissue, is commonly associated with high breast cancer risk.
"We have detected something that is definitely relevant to the health of Latinas, who represent a large percentage of the population in California, and of other states such as Texas," said Laura Fejerman, Ph.D., an assistant professor of medicine and a member of UCSF's Institute of Human Genetics, in a statement to the press. "As a Latina myself, I am gratified that there are representatives of that population directly involved in research that concerns them."
For a long time, data has shown that Latinas are less prone to breast cancer than women of other ethnicities. White women have a 13 percent lifetime risk of breast cancer, black women have about an 11 percent risk, and Hispanic women have a less than 10 percent risk, according to data from the National Cancer Institute recorded from 2007 to 2009.
The lifetime risk among Latinas with indigenous ancestry is even lower, leading researchers to believe that the protective gene mutation may have been passed down from indigenous populations in the Americas.
Fejerman and Ziv looked at data from the Cancer Prevention Institute of California and a study known as the Multiethnic Cohort. They were able to duplicate their initial findings using data from three other studies, which incorporated DNA from 3,140 women who had breast cancer and 8,184 healthy people.
The gene variant is located on Chromosome 6. It is near a gene coding for the estrogen receptor ESR1. Though Fejerman and Ziv do not fully understand the link between lower breast cancer risk and the variant, experiments show that the variant interferes with proteins that regulate ESR1’s expression.
“It is potentially very important as we figure out the specific mechanism by which this polymorphism seems to lower the risk of getting breast cancer,” said Dr. Charles Shapiro, co-director of the Dubin Breast Center at The Mount Sinai Hospital and director of translational breast cancer research for The Mount Sinai Health System. “This study might give us insight on how to further reduce the risk in other populations.”
The researchers are working to pinpoint more risk variants in Latinas and to integrate them into predictive risk models for Latinas in the United States. They are also looking to add tests for the variants during routine breast cancer screenings.
In the meantime, this news doesn’t mean Latinas should forego breast cancer checks.
“Latinas should continue to follow the standard recommendations for breast cancer screening,” Shapiro advised.