October 22, 2014 — A genetic variant that is common among some Latinas with indigenous American ancestry could significantly lower their risk of developing breast cancer, according to a study published Monday in Nature Communications, the New York Times' "Well" reports.
According to "Well," the research is the first genome-wide study to include a significant number of Latinas, whereas previous research focused on women of European dissent. Laura Fejerman, the study's lead author and an assistant professor at the University of California-San Francisco's Institute for Human Genetics, said the Latinas in the study mostly lived in California, Colombia and Mexico.
The National Cancer Institute funded the study, which was led by researchers from UCSF. The researchers conducted a genome-wide association study, scanning and comparing DNA from more than 3,000 women with breast cancer and about 8,200 women without breast cancer from various populations.
The researchers found that a genetic variant associated with breast tissue that appears less dense in mammograms was located on chromosome 6. According to "Well," breast density is a risk factor for breast cancer. The researchers theorize that the variant might affect women's production of estrogen receptors.
According to the study, around one in five U.S. Latinas have one copy of the variant, while about 1% carry two copies. "Well" notes that the findings could shed light on why Latina women have lower breast cancer rates than other U.S. women.
The researchers also found that the frequency of the variant was linked to indigenous ancestry. Specifically, the study found that the variant occurred in Mexican women about 15% of the time, in Colombian women about 10% of the time and in Puerto Rican women about 5% of the time. Meanwhile, the variant occurs in white and African American women at a frequency of less than 1% and in Chinese women at a frequency of about 2%.
According to the study, women who have one copy of the variant are about 40% less likely to develop breast cancer than women who do not have it, while women who have two copies of the variant are about 80% less likely to develop the disease. Women with the variant were particularly less likely to develop an aggressive form of cancer called estrogen-receptor negative.
Study Could Impact Future Treatments, Prevention
Avon Foundation Breast Cancer Crusade Executive Director Marc Hurlbert, who was not involved with the research, said the study is "really important" because "it might help us to develop better treatments for those who do get breast cancer."
Meanwhile, American Cancer Society Chief Medical Officer Otis Brawley said that while the study is based on "very good science," people must "keep in mind that some women with this variant still get breast cancer" (O'Connor, "Well," New York Times, 10/20).
According to the San Francisco Chronicle, research is not yet advanced enough to develop a test for the variant (Colliver, San Francisco Chronicle, 10/21). Elad Ziv, a researcher on the study and a specialist at the UCSF Helen Diller Family Comprehensive Cancer Center, said researchers "really need to do more experiments to" pinpoint the variant and "understand what it is doing" (Lee Hotz, Wall Street Journal, 10/20).