Comparison of genetic variation of breast cancer susceptibility genes in Chinese and German populations

Genome-wide association studies (GWAS) identified several genetic risk factors for breast cancer, however, most of them were validated among women of European ancestry. This study examined single-nucleotide polymorphisms (SNPs) contributing to breast cancer in Chinese (984 cases and 2206 controls) and German (311 cases and 960 controls) populations. Eighteen SNPs significantly associated with breast cancer, previously identified in GWAS were genotyped. Twelve SNPs passed quality control and were subjected to statistical analysis. Seven SNPs were confirmed to be significantly associated with breast cancer in the Chinese population, reflecting three independent loci (ESR1, FGFR2, TOX3) and five of these were also confirmed in the German population. The strongest association was identified for rs2046210 in the Chinese (odds ratio (OR) = 1.42, 95% confidence interval (CI) = 1.28-1.59, P = 1.9 x 10(-10)) and rs3803662 in the German population (OR = 1.43, 95% CI = 1.17-1.74, P = 4.01 x 10(-4)), located upstream of the ESR1 and TOX3 gene, respectively. For the first time, rs3757318 at 6q25.1, located next to the gene encoding estrogen receptor a (ESR1) was found to be strongly associated with breast cancer (OR = 1.33, 95% CI = 1.18-1.49, P = 1.94 x 10(-6)) in the Chinese population. The frequency of this variant was markedly lower in the German population and the association was not significant. Despite the genetic differences, essentially the same risk loci were identified in the Chinese and the German populations. Our study suggested the existence of common genetic factors as well as disease susceptibility differences for breast cancer in both populations and highlighted the importance of performing comparison analyses for disease susceptibility within ethnic populations.