Abstract
Dysregulation of microRNA expression in breast cancer (BC) has been associated with molecular disturbances involved in cancer initiation, progression and metastasis. Specific microRNAs also act as endocrine modulators in BC, thereby influencing the biological behavior of the tumor and drug responses. Our objective was to employ bioinformatics tools to identify and characterize microRNAs acting as candidate players involved in epithelial-mesenchymal transition, migration, invasion, and/or hormonal regulation in BC. We systematically integrated microRNA profiling data from three different studies on BC cell lines with different invasive capabilities and from another study on lymph node metastases and matching primary BC, resulting in five microRNA hits-DE-microRNAs miR-146a-5p, miR-222-3p, miR-205-5p, miR-141-3p and miR-200c-3p. This set of microRNAs was evaluated for clinical significance in BC and subjected to target prediction, microRNA-mRNA network construction, functional enrichment analysis and quantification in BC cell lines by qPCR. An upregulated DE-microRNA, miR-222-3p, displayed distinctive pro-metastatic features, supported by its clinical relevance, as well as by the results of the functional enrichment analysis of its target genes. Downregulation of the members of the miR-200 family and miR-205-5p were significantly associated with negative clinical features, while their targets were enriched with genes that were relevant to cancer aggressiveness. These results are in line with the presumed functional relevance of the selected DE-microRNAs in BC.