Role of miRNAs in Triple-Negative Breast Cancer: Diagnosis, Prognosis, and Treatment

MicroRNAs (miRNAs) are small noncoding RNAs that regulate cellular normal function and physiology. There is increasing evidence indicating that miRNAs regulate pathways involved in cancer initiation and progression. Recently, the expression patterns of miRNAs have been used as biomarkers in diagnosing various cancers including breast cancer. MiRNAs are highly stable and can be found in various human samples including blood, serum, urine, and tissues. Also, the correlation between clinicopathological features and the level of expression makes them more suitable biomarkers. Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer. The lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) receptors has made TNBC treatment more challenging. Increasing the expression of miRNAs with oncogenic activities (OncomiRs) and decreasing the expression of miRNAs with tumor-suppressing features are related to TNBC pathophysiology. Investigating miRNAs relating to TNBC development could lead to finding novel ways in diagnosis, prognosis, and treatment of TNBC; thus, this study aims to review the mechanisms and roles of miRNAs in TNBC.