Exosomal miRNAs as Next-generation Therapy Vehicles in Breast Cancer.

The second most pervasive cancer affecting the survival of women across the world is breast cancer. One of the biggest challenges in breast cancer treatment is the chemoresistance of cancer cells to various medications after some time. Therefore, highly specific blood-based biomarkers are required for early breast cancer diagnosis to overcome chemoresistance and improve patient survival. These days, exosomal miRNAs have attracted much attention as early diagnostic blood-based biomarkers because of their high stability, secretion from malignant tumor cells, and excellent specificity for different breast cancer subtypes. In addition, exosomal miRNAs regulate cell proliferation, invasion, metastasis, and apoptosis by binding to the 3'UTR of their target genes and limiting their production. This review focuses on the functions of exosomal miRNAs in tumorigenesis via targeting multiple signaling pathways as well as chemosensitivity and resistance mechanisms. In addition, the growing pieces of evidence discussed in this review suggest that circulating exosomal miRNAs could be utilized as potential next-generation therapeutic target vehicles in the treatment of breast cancer.