MicroRNA expression analysis in triple-negative (ER, PR and Her2/neu) breast cancer

miRNAs are small, regulatory molecules approximately 21-24 nucleotides in length. They function at the post-transcriptional level by controlling the expression of more than 50% of human protein-coding genes and play an essential role in cell signaling pathways. The objective of the present study was to explore the expression profile of oncomiRs and tumor-suppressor miRs, and to define their possible correlations in triple-negative (ER, PR and Her2/neu) primary breast cancers. miR-21, miR-210 and miR-221 were significantly overexpressed, whereas miR-10b, miR-145, miR-205, miR-122a were significantly underexpressed in the triple-negative primary breast cancers. Significant correlations among all of the studied miRs were scored both in the breast cancer and control tissue. Expression of miR-222 and miR-296 did not exhibit any significant difference between the breast cancer and normal tissue. There was a non-significant trend for high expression levels of the microRNAs, miR-21, miR-210, miR-221 and miR-222, to be associated with worse patient disease-free and overall survival. Forty-nine primary triple-negative breast cancer cases, along with 34 matched tumor-associated normal samples were investigated for the expression of 9 miRNAs using qPCR. Relationships between the expression of miR-10b, miR-21, miR-122a, miR-145, miR-205, miR-210, miR-221, miR-222 and miR-296 and the pathologic features of the tumors were examined, as were the influences of miR expression on patient overall and cancer-specific survival. miR-21, miR-210 and miR-221 expression plays a significant role in triple-negative primary breast cancers.