Integration of BRCA1-mediated miRNA and mRNA profiles reveals microRNA regulation of TRAF2 and NFκB pathway.

Microarray-based techniques are being useful to obtain miRNA and gene expression signatures associated with different tumors. BRCA1 deregulation is a frequent event in the pathogenesis of breast as well as other cancers. In addition to DNA repair functions of BRCA1, it is involved in a wide range of cellular processes such as cell cycle, chromatin remodeling or transcription. However, the molecular events underlying BRCA1-associated tumorigenesis are still largely unknown. In order to deepen our understanding of BRCA1-associated tumorigenesis, we integrated data from mRNA and miRNA microarray experiments on HCC1937 breast cancer cell line, and the isogenic HCC1937 stably expressing BRCA1, to obtain significant miRNA-mRNA relationships associated with the presence of BRCA1 gene. By using bioinformatic integration of gene and miRNA expression data, we found significant miRNA-gene relationships underlying the array signatures. We additionally evaluated the role of these statistically significant pairs at the biological pathways level and identified MAPK and NF-κB pathways associated with these expression changes. Furthermore, we experimentally validated miRNAs induced by BRCA1 that commonly regulate TRAF2, a key regulator of NF-κB and MAPK pathways. We demonstrate that miR-146a, miR-99b and miR-205, induced in HCC1937 BRCA1-expressing cells, bind and regulate TRAF2 gene. In addition, re-expression of miR-146a, miR-99b or miR-205 in HCC1937 BRCA1-null cells was sufficient to modulate NF-κB activity. Our results demonstrate that integration of mRNA and miRNA associated with BRCA1 expression was useful to discover new miRNA-gene interactions as molecular events underlying BRCA1-mediated tumorigenesis.