Refinement of the 22q12-q13 breast cancer--associated region: evidence of TMPRSS6 as a candidate gene in an eastern Finnish population.

Although many risk factors for breast cancer are known, most of the genetic background and molecular mechanisms still remain to be elucidated. We have previously published an autosome-wide microsatellite scan for breast cancer association and here we report a follow-up study for one of the detected regions. Ten single nucleotide polymorphisms (SNP) were genotyped in an Eastern Finnish population sample of 497 breast cancer cases and 458 controls to refine the 550-kb region on 22q12-q13 and identify the breast cancer-associated gene(s) in this region. We also studied 22q12-q13 for allelic imbalance for the detection of a possible tumor suppressor gene and to see whether the breast cancer association and allelic imbalance in this region could be connected. A SNP (rs733655) in matriptase-2 gene (TMPRSS6) was detected to associate with breast cancer risk. The genotype frequencies of rs733655 differed significantly between cases and controls in the entire sample and in the geographically and genetically more homogeneous subsample with P = 0.044 and P = 0.0003, respectively. The heterozygous genotype TC was observed to be the risk genotype in both samples (odds ratios, 1.39; 95% confidence intervals, 1.06-1.83 and odds ratios, 2.11; 95% confidence intervals, 1.46-3.05). An associated two-marker haplotype involving SNP rs733655 (empirical P = 0.041) provides further evidence for breast cancer risk factor locating on 22q12-q13, possibly being TMPRSS6. Our results suggest that matriptase-2 gene is associated with breast cancer risk in the Eastern Finnish population.