MicroRNA-21 as an indicator of aggressive phenotype in breast cancer.

Abstract

e11010 Background: MicroRNAs (miRNAs) are a new class of non-protein-coding, endogenous, small RNAs. They have clinical significance because of their relationship to cancer pathogenesis. miRNAs act as an oncogene or a tumour supressor gene in cancer pathogenesis. MicroRNA-21 (miR-21) shows the highest expression level and acts as an oncogene in breast cancer. The purposes of this study are to measure miR-21 expression in early-stage breast cancer and to analyze its association with clinicopathologic features. Methods: Formalin-Fixed, Paraffin-Embedded (FFPE) tissue samples were collected from 15 patients who underwent surgery for primary breast cancer. The expression level of miR-21 was measured by the real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis in the tumor tissue and normal breast tissue. Levels of miR-21 expression in terms of disease stage, tumor size, nodal involvement, hormone receptor status and HER2 status were compared. Results: miR-21 expression was detected in all tumor samples and the level of miR-21 expression was higher than the normal breast tissue samples (p=0,001). There were no significant differences among miR-21 expression levels in terms of tumor size and hormone receptor status, but significant differences were observed in terms of nodal involvement (p=0.037), disease stage (p=0.005) and HER2 status (p=0.014). The expression level of miR-21 was higher in patients with four or more nodal involvement, patients with Stage III and HER2-positive patients than in patients with three or less nodal involvement, patients with Stage I or II and HER2-negative patients, respectively. Conclusions: These findings suggest that microRNA-21 is expressed in breast cancer and the high expression level of miR-21 is associated with more nodal involvement, more advanced disease stage and HER2-positive status. These results demonstrate that high expression level of miR-21 indicates a more aggressive phenotype of breast cancer. miR-21 may play an important role in breast cancer progression and therefore it may be a novel therapeutic target for the treatment of breast cancer.