Use of gene expression profiles of peripheral blood lymphocytes to distinguish BRCA1 mutation carriers in high risk breast cancer families.

Mutations in two major genes, BRCA1 and BRCA2, account for up to 30% of families with hereditary breast cancer. Unfortunately, in most families there is little to indicate which gene should be targeted first for mutation screening, which is labor intensive, time consuming and often prohibitively expensive. As BRCA1 is a tumor suppressor gene involved in various cellular processes, heterozygous mutations could deregulate dependent pathways, such as DNA damage response, and disturb transcriptional activity of genes involved in the downstream signaling cascade. We investigated gene expression profiling in peripheral blood lymphocytes to evaluate this strategy for distinguishing BRCA1 mutation carriers from non-carriers. RNA from whole blood samples of 15 BRCA1 mutation carriers and 15 non-carriers from BRCA1 or BRCA2 families were hybridized to Agilent Technologies Whole Human Genome OligoMicroarrays (4 x 44 K multiplex format) containing 41,000 unique human genes and transcripts. Gene expression data were analyzed with Welch's t-tests and submitted to hierarchical clustering (GeneSpring GX software, Agilent Technologies). Statistical analysis revealed a slight tendency for 133 genes to be differentially expressed between BRCA1 mutation carriers and non-carriers. However, hierarchical clustering of these genes did not accurately discriminate BRCA1 mutation carriers from non-carriers. Expression variation for these genes according to BRCA1 mutation status was weak. In summary, microarray profiling of untreated whole blood does not appear to be informative in identifying breast cancer risk due to BRCA1 mutation.