Pathophysiology rolesr and translational opportunities of miRNAs in breast cancer

Last decades have witnessed a constant interest of the scientific community in the biology of microRNAs and their involvement in both physiological and pathological processes. Small noncoding RNAs able to finely tune gene expression at posttranscriptional level, microRNAs play indeed crucial roles in essential phenomena such as proliferation, apoptosis, differentiation, migration, metabolism, immune system activity. Their altered expression in pathological conditions, as cancer for instance, has raised the intriguing idea to exploit them as clinically relevant tools: as diagnostic, prognostic, or predictive biomarkers, as well as targets for an innovative therapy. Herein, we review and discuss the involvement of microRNAs in both mammary gland physiology and pathology. Several microRNAs have been indeed functionally linked to different steps of mammary gland morphogenesis and functionality. An increasing body of evidence also correlates microRNAs to breast cancer occurrence, progression, resistance to therapies, and analyzes their functional role in acting as oncogenes or oncosuppressor microRNAs in neoplastic cells and/or in the microenvironment.