Identification of microRNA biomarkers in the blood of breast cancer patients based on microRNA profiling.

Accumulating evidence indicates that human circulating microRNAs (miRNAs) could serve as diagnostic and prognostic biomarkers in various cancers. We aimed to explore novel miRNA biomarkers in the blood of breast cancer patients based on miRNA profiling. A miRCURY™ LNA Array was used to identify differentially altered miRNAs in the whole blood of breast cancer patients (n=6) and healthy controls (n=6). Levels of candidate miRNAs were quantified by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in whole blood specimens of 15 breast cancer patients and 13 age-matched healthy control individuals. The miRWalk database was used to predict miRNA targets and the DAVID tool was used to identify significant enrichment pathways. A total of 171 differentially expressed miRNAs were identified by microarray, including 169 upregulated and 2 downregulated miRNAs in breast cancer. Five upregulated miRNAs (miR-30b-5p, miR-96-5p, miR-182-5p, miR-374b-5p, and miR-942-5p) were confirmed by qRT-PCR. The areas under the receiver operating characteristic curve of miR-30b-5p, miR-96-5p, miR-182-5p, miR-374b-5p, and miR-942-5p were 0.9333, 0.7692, 0.7590, 0.8256, and 0.8128, respectively. Importantly, upregulation of these five miRNAs was observed even in patients with very early-stage breast cancer. A total of 855 genes were predicted to be targeted by the five miRNAs, and the one cut domain family member 2 gene (ONECUT2) was a shared target of the five miRNAs. Analysis of publicly available data revealed that these dysregulated miRNAs and the target genes were associated with the survival of breast cancer patients. Furthermore, the five miRNAs were significantly enriched in numerous cancer-related pathways, including "MicroRNAs in cancer", "Pathways in cancer", "FoxO signaling pathway", "Ras signaling pathway", "Rap1 signaling pathway", "MAPK signaling pathway", and "PI3K-Akt signaling pathway". Our data support the potential of the five identified miRNAs as novel biomarkers for the detection of breast cancer, and indicate that they may be involved in breast cancer development and progression.