A miRNA microarray covering 2019 mature miRNAs was used to identify differentially-expressed miRNAs in nine patients with LNM and three patients without LNM. Thirty-five differentially expressed miRNAs were identified, of which 10 significantly were up-regulated while the other 25 were down-regulated in tissues with LNM compared to those without LNM. Seven miRNAs were subjected to quantitative real-time polymerase chain reaction PCR (qRT-PCR) and four miRNAs (miR-191-5p, miR-214–3p, miR-451a and miR-489) were validated in a total of 159 patients including a training set (n = 64) and a validation set (n = 95). The four miRNAs were used to construct a miRNA signature by Logistic regression. Risk scores derived from the four-miRNA signature were calculated to stratify the patients into high- or low-risk groups. Patients with high-risk scores had poorer overall survival (OS) and disease-free survival (DFS) than those with low-risk scores. The miRNA signature was an independent prognostic factor. MiR-191 increased whereas miR-214–3p, miR-451a and miR-489 inhibited cell proliferation, migration, and invasion abilities.
This four-miRNA signature may be a reliable prognostic and predictive tool for metastasis and survival in breast cancer patients.