Genetic variant protects some Latinas from breast cancer

Oct. 24, 2014

An international research collaboration led by UC San Francisco researchers has identified a genetic variant common in Latina women that protects against breast cancer. The variant, a difference in just one of the three billion “letters” in the human genome known as a single-nucleotide polymorphism (SNP), originates from indigenous Americans and confers significant protection from breast cancer, particularly the more aggressive estrogen receptor–negative forms of the disease, which generally have a worse prognosis.

The newly discovered SNP is on Chromosome 6, near a gene coding for an estrogen receptor called ESR1. Researcher say that the biological basis of the association between the variant and reduced breast cancer risk is still not known, but their preliminary experiments indicate that the variant interferes with the action of transcription factors, proteins that regulate the expression of the ESR1 estrogen receptor.

“The effect is quite significant,” says Elad Ziv, MD, senior author of the study. “If you have one copy of this variant, which is the case for approximately 20% (the range being 10 to 25 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% of the U.S. Latina population, the reduction in risk is on the order of 80 percent.”

Published recently in Nature Communications, the new study showed that women who carry the variant have breast tissue that appears less dense on mammograms. High “mammographic density” is a known risk factor for breast cancer. Read the study abstract.

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