Gene expression profiling of breast tumors by use of DNA microarrays has been employed to refine classification. Evidence suggests that distinct expression patterns reflect divergent pathways of tumor progression from origins in epithelial progenitor cells and corresponding biological and clinically relevant subtypes have been identified. Germline mutations in BRCA1 and BRCA2 predispose to breast and other cancers and associated tumors display characteristic features including gene expression patterns. Processes in which the BRCA proteins partake are disrupted by numerous mechanisms and consequential tumor traits are found in sporadic cancers. Here we have characterized variation in gene expression patterns in a set of surgical specimens of sporadic cases that represents the diverse group of disease entities collectively termed breast cancer and have analyzed expression profiles from BRCA1 and BRCA2 associated cases in this context. We show that tumors associated with germline BRCA mutations display expression patterns that are in common with discrete breast cancer subtypes including sporadic cases. These common traits might have important implications for our understanding of breast cancer biology and for targeting disease treatment.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]