Association between Ancestry-Specific 6q25 Variants and Breast Cancer Subtypes in Peruvian Women

Abstract

Background:

Breast cancer incidence in the United States is lower in Hispanic/Latina (H/L) compared with African American/Black or Non-Hispanic White women. An Indigenous American breast cancer–protective germline variant (rs140068132) has been reported near the estrogen receptor 1 gene. This study tests the association of rs140068132 and other polymorphisms in the 6q25 region with subtype-specific breast cancer risk in H/Ls of high Indigenous American ancestry.

Methods:

Genotypes were obtained for 5,094 Peruvian women with (1,755) and without (3,337) breast cancer. Associations between genotype and overall and subtype-specific risk for the protective variant were tested using logistic regression models and conditional analyses, including other risk-associated polymorphisms in the region.

Results:

We replicated the reported association between rs140068132 and breast cancer risk overall [odds ratio (OR), 0.53; 95% confidence interval (CI), 0.47–0.59], as well as the lower odds of developing hormone receptor negative (HR ⁻) versus HR ⁺ disease (OR, 0.77; 95% CI, 0.61–0.97). Models, including HER2, showed further heterogeneity with reduced odds for HR ⁺HER2 ⁺ (OR, 0.68; 95% CI, 0.51–0.92), HR ⁻HER2 ⁺ (OR, 0.63; 95% CI, 0.44–0.90) and HR ⁻HER2 ⁻ (OR, 0.77; 95% CI, 0.56–1.05) compared with HR ⁺HER2 ⁻. Inclusion of other risk-associated variants did not change these observations.

Conclusions:

The rs140068132 polymorphism is associated with decreased risk of breast cancer in Peruvians and is more protective against HR ⁻ and HER2 ⁺ diseases independently of other breast cancer-associated variants in the 6q25 region.

Impact:

These results could inform functional analyses to understand the mechanism by which rs140068132-G reduces risk of breast cancer development in a subtype-specific manner. They also illustrate the importance of including diverse individuals in genetic studies.