Hispanic women who descend from indigenous Americans may have less probability of developing breast cancer than women from other ethnicities, according to a study conducted at the University of California, San Francisco (UCSF). The study found a genetic variant particularly common in these women lowers the risk dramatically.
In addition, the researchers were able to determine that about one in each five Latina women living in the United Stated carry at least one cope of that variant, and one percent carry two.
Even though the researchers haven’t been able to fully understand the function of the genetic variant, the study demonstrated that women who carry the gene have less dense breast tissue, according to the mammograms conducted, which is a crucial factor in the development of the disease. The research team believes that the genetic variant may influence the production of estrogen receptors.
Focusing on the chromosome 6, the scientists found the protective variant, a single nucleotide polymorphism (SNP), was present in about 15 percent of women with Mexican descendant, 10 percent in Colombian and 5 percent in Puerto Rican. However, the frequency of SNP in either white and black women was only one percent and two percent in Chinese women.
“My expectation would be that if you go to a highly indigenous region in Latin America, the frequency of the variant would be between 15 and 20 percent,” the lead author of the study, Laura Fejerman of the Institute for Human Genetics in San Francisco, said in a news release. “But in places with very low indigenous concentration, places with high European ancestry, you might not even see it.”
Moreover, the study, titled “Genome-wide association study of breast cancer in Latinas identifies novel protective variants on 6q25“, published in Nature Communications, was able to determine that carrying one copy of the variant gene represents having about 40 percent less risk of developing breast cancer, while carrying two copies doubles the protection. The influence of the gene in lowering the risk was particularly significant in estrogen-receptor negative breast cancer, which is an aggressive form of the disease.
The study looked into the hypothesis that the reduced risk could be related to behavioural factors, as Hispanic women are also less likely to resource to postmenopausal hormones, and more likely to give birth to more children and at younger ages.
The team scanned the DNA of 3,000 breast cancer female patients and compared it with 8,200 women control patients from different ethnicities, in order to conduct a genome-wide association study meant to assess the correlation between genetic variations and breast cancer. Even though other studies had already analyzed the genetics of women with European descendant, this was the first time that the Hispanic ethnicity was studied at such a large scale.
“I’m confident that this finding is going to hold, that most women who have this genetic variant are at lower risk of breast cancer,” the chief medical officer at the American Cancer Society, Dr. Otis W. Brawley added in the news release. “But keep in mind that some women with this variant still get breast cancer. It might be because they have this variant and something else that cancels it out.”
The findings may help not only better understand genetics, ethnicity and breast cancer, but also develop treatments for the disease. In addition, it can also explain the disease rates demonstrating that less Hispanic women suffer from breast cancer than other Americans. Hispanic have a 10 percent risk of developing breast cancer, while white women have a 13 percent risk and black women 11 percent, according to federal data.
The Center for Breast Surgery at the University of Texas Southwestern Medical Center has recently announced it was looking for Hispanic women who survived breast cancer, for patient enrollment on a large study, which is expected to be able to determine risk factors associated with triple negative breast cancer, one of the most difficult types of cancer to treat, as well as compare genetic resemblances of ethnic groups.