Exosomal microRNA: a novel biomarker for breast cancer

Breast cancer is the most common invasive malignancy among females worldwide. microRNAs (miRNAs) are small noncoding RNAs that regulate post-transcriptional gene expression by binding to the 3'-untranslated regions of targeted mRNAs. Recently, exosomes have been recognized to play critical roles in breast cancer. miRNAs, as the most important inclusions in exosomes, are stable in the blood and other body fluids, making them ideal candidate biomarkers. In this review, we provide a complex overview of exosomal miRNAs in breast cancer. Particularly, we summarized their critical roles in tumorigenesis and tumor progression, expecting to lay the foundation for future studies using these potential biomarkers.