Clinical impact of circulating miR-221 in plasma of patients with pancreatic cancer

Background: Several recent studies have demonstrated that microRNAs (miRNAs) are stably detectable in plasma/serum. We tested miR-221 and miR-375, which are frequently reported to be highly and poorly expressed in pancreatic cancer (PCa), as candidates for plasma biomarkers in PCa. Methods: This study was divided into three parts: (1) Confirmation of higher miR-221 levels in primary PCa tissue and cell lines than normal pancreatic tissues. (2) Evaluation of plasma miR-221 and miR-375 concentrations by comparing results from 47 consecutive PCa patients and 30 healthy volunteers. (3) Evaluation of the assay for monitoring tumour dynamics in PCa patients. Results: (1) Expression of miR-221 was significantly higher in PCa tissues and cell lines than normal pancreatic tissues. (2) Plasma miR-221 concentrations were significantly higher in PCa patients than that in benign pancreatic tumours (P = 0.016) and controls (P<0.0005), while plasma miR-375 concentrations tended to be lower in PCa patients (P = 0.064), and the miR-221/miR-375 ratio was significantly higher (P<0.0001) in PCa patients than in controls. (3) Plasma miR-221 concentrations were significantly reduced in postoperative samples (P = 0.018). Furthermore, PCa patients with high plasma miR-221 concentrations had significant correlation with distant metastasis (P = 0.041), and non-resectable status (P = 0.021). Conclusion: Plasma miR-221 could be a useful biomarker for cancer detection, monitoring tumour dynamics and predicting malignant outcomes in PCa patients, and may contribute to clinical decision making in PCa treatments.