V Scholar Discovers Link Between Hispanic Women and Lower Breast Cancer Risk
Article by Carole C. Wegner, PhD
Doctors have long known Hispanic women have a lower risk of breast cancer compared to women of African American or European ancestry. An average of 90.8 women in every 100,000 Hispanic women develop breast cancer, while 121 women in every 100,000 African American women and 133 women in every 100,000 Caucasian women develop breast cancer. But, the basis of this ethnic and racial difference was not known. Dr. Luis Carvajal-Carmona, a 2013 V Scholar grant recipient from the University of California, Davis, and his colleagues have found a BRCA1 mutation or variant in the genetic sequence upstream of the estrogen receptor gene on Chromosome 6 that may partly explain this phenomenon.
Dr. Luis Carvajal-Carmona (right)
Photo courtesy of UC-Davis
The genetic variation is a single nucleotide polymorphism, or SNP (pronounced ‘snip’), which means a single letter of the DNA alphabet is changed in a sequence of letters to produce the variant. This variant is relatively common in Latin American populations (5% in Puerto Ricans, 10% in Columbians and 14% in Mexicans) but is almost absent from people of European, African American and Chinese heritage. According to studies performed by the team, women who carry just one copy, or allele, of the variant were 40% less likely to develop breast cancer. If both alleles of the genetic sequence are of the variant sequence, the protective effect doubles. Interestingly, women who have this protective genetic variant also have less dense-appearing breast tissue on mammograms. Women with less dense breast tissue have a lower risk of developing breast cancer.
Behavioral factors more common in Hispanic women, such as having more children at younger ages and using fewer post-menopausal hormones, are other factors that contribute to a reduced breast cancer risk in this ethic group.
Identification of this protective variant and mapping of other BRCA1 and BRCA2 mutations in Hispanic women could translate into genetic-based cancer prevention efforts in these women.
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