Anahad O'Connor in The New York Times:
A genetic variant that is particularly common in some Hispanic women with indigenous American ancestry appears to drastically lower the risk of breast cancer, a new study found. About one in five Latinas in the United States carry one copy of the variant, and roughly 1 percent carry two.
…Many genome-wide association studies have looked for associations with breast cancer in women of European descent. But this was the first such study to include large numbers of Latinas, who in this case hailed mostly from California, Colombia and Mexico, said the lead author of the study, Laura Fejerman of the Institute for Human Genetics in San Francisco. The researchers zeroed in on chromosome 6 and discovered the protective variant, which is known as a single nucleotide polymorphism, or SNP (pronounced (“snip”). They also discovered that its frequency tracked with indigenous ancestry. It occurred with about 15 percent frequency in Mexico, 10 percent in Colombia and 5 percent in Puerto Rico. But its frequency was below 1 percent in whites and blacks, and other studies have shown that it occurs in about 2 percent of Chinese people. “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,” Dr. Fejerman said. “But in places with very low indigenous concentration — places with high European ancestry — you might not even see it.”