Abstract LB-299: Genome wide association study of breast cancer in Latinas identifies protective variants of Indigenous American origin on 6q25
Authors: Fejerman Laura , Ahmadiyeh Nasim , Hu Donglei , Huntsman Scott , Beckman Kenneth , Caswell Jennifer , John Esther M. , Torres-Mejia Gabriela , Carvajal-Carmona Luis , Echeverry Magdalena , Tuazon Anna Marie , Ramirez Carolina ,   COLUMBUS Consortium, Gignoux Christopher , Eng Celeste , Gonzalez-Burchard Esteban , Henderson Brian , Marchand Loic L. , Perez-Stable Eliseo J. , Haiman Christopher A. , Ziv Elad 
Published: May 2015

Background: Multiple breast cancer genome-wide association studies (GWAS) have been conducted, with most samples analyzed being of European or Asian origin. No GWAS has been published to date on US Latinas or Latin American women. Previous studies have demonstrated that among Latina women, those with the highest Indigenous American ancestry are protected from breast cancer. We performed the first genome-wide association study of breast cancer in Latinas in a total of 1523 cases and 3221 controls and validated the strongest associations in an additional 977 Latina cases and 1158 controls.

Methods: For the discovery phase, samples were genotyped with either the 6.0 Affymetrix array or Illumina Infinitum 660W/Omni 2.5 arrays. Additional genotypes were imputed from 1000 genomes and the final analysis included ∼7 million SNPs. SNPs for replication were genotyped using Sequenom. Logistic regression analyses included the first 10 principal components as covariates.

Results: We identified two new variants, located 5’ of the ESR1 gene (6q25 region), which are strongly associated with breast cancer in this population. The minor allele for these variants is strongly protective (rs140068132: OR 0.61, 95%CI 0.48-0.75, p=3x10-13 & rs147157845: OR 0.63 95% CI 0.49-0.76; p =2x10-12). These alleles are present only in Latinos, correlate with Indigenous American ancestry, and are uncorrelated with previously reported risk variants in the ESR1 region. We found a strong association for both ER-positive and ER-negative breast cancer, but significantly more protection for ER-negative disease (p=0.014). The rs140068132 variant is also associated with breast density. The average breast density among women who are homozygous for the protective allele is approximately half of that of women homozygous for the common allele [Mean (sd) density for Homozygous GG = 9 (8); Homozygous AA = 17 (14), p 0.0009]. rs140068132, is located within a putative binding region for multiple transcription factors. MAPPER predicts disruption of putative transcription factor binding sites for the rare allele at rs140068132 but not rs147157845. Electromotility shift assays showed differential binding of the two alleles at the rs140068132 locus, with the protective allele (G) showing substantially reduced binding affinity compared to the common A allele.

Conclusions: The variants at this locus represent, to our knowledge, the strongest genome wide effect size on breast cancer for a common variant (frequency &gt;0.05 in any major population). These results may help in understanding the previous observations of lower breast cancer risk among Latina women with more Indigenous American ancestry and highlight the importance of conducting GWAS in diverse populations.

Citation Format: Laura Fejerman, Nasim Ahmadiyeh, Donglei Hu, Scott Huntsman, Kenneth Beckman, Jennifer Caswell, Esther M. John, Gabriela Torres-Mejia, Luis Carvajal-Carmona, Magdalena Echeverry, Anna Marie Tuazon, Carolina Ramirez, COLUMBUS Consortium, Christopher Gignoux, Celeste Eng, Esteban Gonzalez-Burchard, Brian Henderson, Loic Le Marchand, Eliseo J. Perez-Stable, Christopher A. Haiman, Elad Ziv. Genome wide association study of breast cancer in Latinas identifies protective variants of Indigenous American origin on 6q25. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-299. doi:10.1158/1538-7445.AM2014-LB-299