Multiplex genotyping of 1107 SNPs from 232 candidate genes identified an association between IL1A polymorphism and breast cancer risk

We sought to identify genes and polymorphisms associated with breast cancer risk among Korean women using multiplex genotyping. The SNPs (n=1536) of 264 candidate genes were genotyped using the Illumina Golden Gate™assay. These genes are involved in the pathways controlling apoptosis/anti-apoptosis, the immune and inflammatory responses, cytokines, DNA repair, cell adhesion, and cell cycle/proliferation. Breast cancer cases (n=209) were recruited from Seoul National University Hospital. Agematched control subjects (n=209) were selected from a health examinees cohort. Gene-based and SNP-based tests were performed. The final analysis includes 117 cases and 164 controls with 1107 SNPs in 232 genes. Gene-based analyses showed that IL1A, TNFRSF10B, TNFRSF1B, ICAM, and TNFSF9 were significantly associated with breast cancer risk (p<0.01). IL1A was the most significant gene associated with breast cancer risk [p for likelihood ratio test, 1 degree of freedom (df)=6x10^-7; FDR-adjusted p-value, 1df=4x10^-4, 2df=0.0071, respectively]. Individual SNP-based analyses revealed that the rare allele of the IL1A SNP rs2856836, Ex7-592T→C, was strongly associated with breast cancer risk (FDR-adjusted p-value, 1df=0.0027, 2df=0.0162). This SNP was found to increase risk for breast cancer [odds ratio (OR)=2.88, 95% confidence interval (CI)=1.58-5.27 for heterozygote and OR=8.17, 95% CI=2.23-29.99 for rare homozygote]. In summary, we identified a common genetic variant in IL1A strongly associated with breast cancer risk.