A multinational genome-wide association study has identified novel loci for breast cancer susceptibility. Despite the identification of the major susceptibility genes BRCA1 and BRCA2 in the 1990s, the majority of multiple-case breast cancer families do not exhibit mutations in these genes. To identify further susceptibility alleles, researchers conducted a three-stage analysis. The first two stages included a susceptibility study of over 8000 breast cancer patients and controls. In the third part of the study, 30 single nucleotide polymorphisms were tested for confirmation in over 44 000 cases and controls. Five novel breast cancer susceptibility loci were identified, and patterns of risk established for the genes. Although most previously identified genes are associated with DNA repair, the susceptibility loci in this study contain genes related to the control of cell growth or signalling. The authors comment that the results demonstrate the critical importance of study size in such genetic association studies.
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