Genetic Variant Lowers Breast Cancer Risk for Some Latina Women

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Research suggests that a genetic variant in some Latina women may reduce breast cancer risk by 40% to 80%.

The study was published online on Oct. 20, 2014 by Nature Communications. Read “Genome-wide association study of breast cancer in Latinas identifies novel protective variants on 6q25.”

Other studies have shown that Latina women are less likely than white or black women to be diagnosed with breast cancer. According to information from the National Cancer Institute:

  • White women have about a 13% lifetime risk of breast cancer.
  • Black women have about an 11% lifetime risk of breast cancer.
  • Hispanic women have a less than 10% lifetime risk of breast cancer.
  • Hispanic women with indigenous American ancestry have a lower lifetime risk than Hispanic women in general.

So the researchers who did this study wanted to know if there were genetic reasons why Hispanic women have lower breast cancer risk.

They analyzed genetic information from women of different ethnicities from a number of countries, including Mexico, Colombia, and Puerto Rico, both with and without breast cancer.

They found a genetic variant called a single-nucleotide polymorphism (SNP). SNPs are the most common type of genetic variant. Each SNP is a difference in a single building block of DNA (called a nucleotide). SNPs happen normally in our DNA -- scientists estimate that a SNP happens once in every 300 nucleotides, which means there are about 10 million SNPs in the human genome. Most SNPs have no effect on health or development, but some, like the one the researchers found in Latinas, may have important health implications.

According to Elad Ziv, M.D., professor of medicine at the University of California-San Francisco and lead author of the study, women who have one copy of the SNP -- about 10% to 25% of the U.S. Latina population -- are about 40% less likely to be diagnosed with breast cancer. Women who have two copies of the SNP -- about 1% of the U.S. Latina population -- are about 80% less likely to be diagnosed with breast cancer.

The researchers found that the likelihood that a woman would have the SNP was linked to indigenous ancestry:

  • About 15% of Mexican women in the study had the SNP.
  • About 10% of Colombian women in the study had the SNP.
  • About 5% of Puerto Rican women in the study had the SNP.
  • Fewer than 1% of black and white women in the study had the SNP.
  • Other studies have shown that about 2% of Chinese women have the SNP.

The new SNP is on chromosome 6, near a gene that controls an estrogen receptor called ESR1. It’s not completely clear what the SNP does, but it may affect the production of estrogen receptors. Also, women who have the SNP have breast tissue that looks less dense on mammograms.

Dense breasts have less fatty tissue and more non-fatty tissue compared to breasts that aren't dense. Women with dense breasts can be 6 times more likely to develop cancer.

The results of this study are very interesting and may help explain why Latina women have a lower risk of breast cancer than other ethnicities. Still, this genetic variant doesn’t offer complete protection from breast cancer. Some women who have the SNP are still diagnosed with breast cancer.

So no matter your ethnicity, it makes sense to do everything you can to keep your risk of breast cancer as low as it can be. Some lifestyle choices you can make are:

  • getting to and maintaining a healthy weight
  • exercising regularly (about 4 to 7 hours per week at a moderate or intense level)
  • limiting or avoiding alcohol
  • eating nutritious, non-processed food
  • never smoking (or quitting if you do smoke)

For more information on risk-reduction steps you can take, visit the Breastcancer.org Lower Your Risk section.


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