MicroRNAs have emerged as a new class of non-coding genes involved in regulating cell proliferation, differentiation and viability. Recent studies have identified miR-210 as one of a set of hypoxia-regulated microRNAs and demonstrated a direct regulatory role of HIF-1 alpha for its transcription. Here, we assessed miR-210 expression in Japanese triple-negative breast cancers and determined its clinical significance. TaqMan MicroRNA assays for miR-210 expression were performed on 161 samples of Japanese breast cancer tissue (58 triple-negative breast cancer and 103 estrogen receptor positive/HER2 negative). Correlations between miR-210 expression and clinicopathological factors were analyzed. The effects of several variables on survival were tested by a Cox proportional hazards regression analysis. miR-210 expression in triple-negative breast cancers was significantly higher than in estrogen receptor-positive/HER2-negative breast cancers (P < 0.001). Patients whose triple-negative breast cancers showed low miR-210 expression experienced significantly better disease-free and overall survival than those with high miR-210 expression (P = 0.02 and P = 0.05, respectively). Although the prognosis of patients with triple-negative breast cancers is poor, Cox univariate and multivariate analyses demonstrated that a higher expression of miR-210 was an independent factor indicating a worse prognosis than for patients with a low level of miR-210. The degree of miR-210 expression might be a clinically useful prognostic factor for decision-making regarding treatment in the adjuvant setting, especially in node-negative triple-negative breast cancer patients.
