Association of high miR-27a, miR-206, and miR-214 expression with poor patient prognosis and increased chemoresistance in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) represents the most aggressive breast cancer subtype, associated with early metastasis and recurrence as well as poor patient outcome. TNBC does not or weakly respond to hormonal or HER2-targeted therapies. Therefore, there is a strong need to identify other potential molecular targets for TNBC therapy. Micro-RNAs play important roles in the post-transcriptional regulation of gene expression. Thus, micro-RNAs, displaying an association between elevated expression and poor patient prognosis, may represent candidates for such novel tumor targets. In the present study, we evaluated the prognostic impact of miR-27a, miR-206, and miR-214 in TNBC via qPCR in tumor tissue (n=146). In univariate Cox regression analysis, elevated expression of all three analyzed micro-RNAs was significantly associated with shortened disease-free survival (hazard ratio [HR] for miR-27a: 1.85, P=0.038; miR-206: 1.83, P=0.041; miR-214: 2.06, P=0.012). In multivariable analysis, the micro-RNAs remained independent biomarkers for disease-free survival (HR for miR-27a: 1.99, P=0.033; miR-206: 2.14, P=0.018; miR-214: 2.01, P=0.026). Furthermore, our results suggest that elevated levels of these micro-RNAs are linked to enhanced resistance to chemotherapy. Based on the association of high expression levels with shortened patient survival and increased chemoresistance, miR-27a, miR-206, and miR-214 may represent novel molecular targets for TNBC.