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.