Abstract. MicroRNAs are important in cancer development and progression. In the present study, the clinical significance and function of microRNA-711 (miR-711) expression in breast cancer were investigated. The expression level of miR-711 was analyzed in breast cancer tissue samples using reverse transcription-quantitative polymerase chain reaction. Cell proliferation, colony formation, apoptosis and Transwell assays were performed in breast cancer cell lines transfected with miR-711 mimics or inhibitors, or control sequence. miR-711 was found to be upregulated in 30 formalin-fixed paraffin-embedded breast cancer tissue samples compared with paired non-cancerous breast tissues (P<0.05). Furthermore, a higher miR-711 expression was demonstrated to be associated with poor overall and disease-free survival times in 161 breast cancer patients, and miR-711 was identified as an independent prognostic factor using multivariate Cox regression analysis. In vitro, overexpression of miR-711 resulted in a significant increase in proliferation, colony formation, migration and invasion of breast cancer cells. By contrast, downregulating miR-711 inhibited cell proliferation, colony formation, migration and invasion and enhanced the rate of apoptosis of breast cancer cells. To the best of our knowledge, the present study is the first to demonstrate that miR-711 is an independent prognostic factor and serves an important oncogenic function in breast cancer, suggesting that miR-711 is a potential biomarker of prognosis and a molecular therapeutic target in breast cancer.
IntroductionBreast cancer is the most common cancer and the leading cause of cancer-associated mortality in women worldwide (1). Breast cancer mortality rates have decreased in North America and several European countries over the past 25 years, principally due to earlier detection and improved treatments (2,3). However, in numerous African and Asian countries, the incidence and mortality rates have increased (4). Therefore, mortality from breast cancer remains a significant health issue globally. In general, the primary risk factors for breast cancer in women are old age (>50 years) and circulating estrogen (5). There are two strategies for enhancing the survival of breast cancer patients: Early detection and appropriate treatment. Primary treatments include surgery, radiotherapy, chemotherapy, endocrine therapy and targeted therapy. Studies have shown that the integrated use of a variety of treatments is advantageous to the prognosis of breast cancer patients (6). At present, formulation of a treatment plan, including surgery and adjuvant therapy, is primarily based on clinical stage and the presence of several limited biomarkers, including estrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 (6). However, the tumor-node-metastasis staging system and these biomarkers do not meet the requirements for personalized therapy and/or precise therapy. Identifying biomarkers for precisely predicting prognosis or for future targeted thera...