An international study led by UC San Francisco researchers has identified a gene variant in Latinas that places them at less of a risk for breast cancer. Shutterstock/Kentoh

According to the American Cancer Society, breast cancer will claim 40,000 lives this year. In the Hispanic/Latino community, breast cancer rates are relatively lower than those found in the Caucasian community, as data from the Fred Hutchinson Cancer Research Center cites that Latinas are one-third less likely to have breast cancer than non-Hispanic white women.

A new international study, led by UC San Francisco researchers, has found a reason for the low rates of breast cancer in Latinas: most Hispanic women have a genetic variant, which is believed to have originated from indigenous Americans, that protects them.

"After our earliest studies we thought there might be a genetic variant that led to increased risk in European populations," said Elad Ziv, MD, professor of medicine and senior author of the study. "But what this latest work shows is that instead there is a protective variant in Native American and Latina populations."

The variant is one difference in the three billion "letters" in the human genome, also called a single-nucleotide polymorphism (SNP). According to the study — published in the October 20, 2014 issue of Nature Communicationsthis one variation (located on Chromosome 6, near a gene coding for an estrogen receptor known as ESR1) drastically reduces the risk of breast cancer.

"The effect is quite significant," said Ziv. "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 US Latina population, the reduction in risk is on the order of 80 percent."

More specifically, the study found that women with the genetic variant have breast tissue that is less dense on mammograms. This is significant because "mammographic density" is correlated with breast cancer — high dense breast tissue on mammograms is a risk factor.

"We have detected something that is definitely relevant to the health of Latinas, who represent a large percentage of the population in California, and of other states such as Texas," said first author Laura Fejerman, PhD, assistant professor of medicine and a member of UCSF's Institute of Human Genetics. "This work was done as a collaboration of multiple investigators, many of us originally from Latin America. As a Latina myself, I am gratified that there are representatives of that population directly involved in research that concerns them."

The researchers performed a successive genome-wide association analysis of datasets using DNA data from 3,140 women with breast cancer and 8,184 healthy controls.

"Our breast cancer registry has recruited and followed more than 4,000 breast cancer families. For this study, we provided cases and controls who self-identified as Latina or Hispanic," said CPIC Senior Scientist Esther M. John, PhD, MSPH. "The DNA samples and data shared from these cases, combined with other samples from the San Francisco Bay Area, contributed to a total of 977 breast cancer cases and 722 controls that led to this important genetic discovery."

Currently, the scientists are trying to identify risk variants in Latinas so they can create a predictive risk models for US Latinas.

"If we can use these results to better understand how this protects estrogen receptor-negative breast cancer, that would be interesting and important," Ziv said, "because because right now we have no good way to prevent that type of breast cancer."

While the findings of this study are promising and is great news for women of Hispanic origin, it is important not to forget that breast cancer is still the most commonly diagnosed cancer in Latinas. One of the biggest hurdles for Latinas with breast cancer is early detection, as they are more likely than non-Hispanic white women to be diagnosed at a later stage. Additionally, studies have found that Latinas are more likely to have breast cancer at younger ages, and they also have larger tumors that are harder to treat. As such, it is crucial for Latinas to screen for breast cancer with mammograms and CBE's (Clinical breast exams), while taking into consideration the environmental factors into consideration.

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