Genetic ancestry modifies the association between genetic risk variants and breast cancer risk among Hispanic and non-Hispanic white women

Department of Medicine, Division of General Internal Medicine, Institute for Human Genetics and Helen Diller Family Comprehensive Cancer Center, UCSF, San Francisco, CA 94158, US.
Carcinogenesis (Impact Factor: 5.33). 04/2013; 34(8). DOI: 10.1093/carcin/bgt110
Source: PubMed


US Hispanic women have lower breast cancer incidence than non-Hispanic white (NHW) women. Genetic factors may contribute to this difference. Breast cancer genome-wide association studies (GWAS) conducted in women of European or Asian descent have identified multiple risk variants. We tested the association between 10 previously reported single nucleotide polymorphisms (SNPs) and risk of breast cancer in a sample of 4697 Hispanic and 3077 NHW women recruited as part of three population-based case-control studies of breast cancer. We used stratified logistic regression analyses to compare the associations with different genetic variants in NHWs and Hispanics classified by their proportion of Indigenous American (IA) ancestry. Five of 10 SNPs were statistically significantly associated with breast cancer risk. Three of the five significant variants (rs17157903-RELN, rs7696175-TLR1, rs13387042-2q35) were associated with risk among Hispanics but not in NHWs. The odds ratio (OR) for the heterozygous at 2q35 was 0.75 (95% CI = 0.50-1.15) for low IA ancestry and 1.38 (1.04-1.82) for high IA ancestry (p interaction 0.02). The ORs for association at RELN were 0.87 (0.59-1.29) and 1.69 (1.04-2.73), respectively (p interaction 0.03). At the TLR1 locus the ORs for women homozygous for the rare allele were 0.74 (0.42-1.31) and 1.73 (1.19-2.52) (p interaction 0.03). Our results suggest that the proportion of IA ancestry modifies the magnitude and direction of the association of three of the ten previously reported variants. Genetic ancestry should be considered when assessing risk in women of mixed descent and in studies designed to discover causal mutations.

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Available from: Mariana C. Stern, Nov 28, 2015
    • "In the genetic hypothesis self-identified races are considered as proxies for a specific genetic ancestry associated with specific genetic variants contributing to the risk of complex diseases (e.g. Bustamante, Burchard, & De La Vega, 2011; Fejerman et al., 2013; Kumar et al., 2010). Generally genetic ancestry itself is considered unlikely to be the cause of the population-specific genetic susceptibility , but is taken as a proxy for genetic variants contributing to the risk, which are supposed to be either population-specific or differentially distributed among populations (Aldrich et al., 2012). "
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