Plasma microRNA profiles: identification of miR-25 as a novel diagnostic and monitoring biomarker in oesophageal squamous cell carcinoma

Background: Recent studies have demonstrated that microRNAs are stably detectable in plasma/serum because of their binding to specific proteins or being packaged in secretory particles. This study was designed to detect novel microRNAs in plasma for cancer detection and monitoring using microRNA array-based approaches in oesophageal squamous cell carcinoma (ESCC) patients. Methods: Through the integration of two Toray 3D-Gene microRNA array-based approaches to compare plasma microRNA levels between ESCC patients and healthy volunteers and between preoperative and postoperative ESCC patients, we identified a novel plasma biomarker in ESCC. Results: (1) Eight upregulated and common microRNAs (miR-15b, 16, 17, 25, 19b, 20a, 20b, and 106a) were selected using two high-resolution microRNA array approaches. (2) Test-scale analyses by quantitative RT-PCR validated a significant higher levels of plasma miR-19b (P=0.0020) and miR-25 (P=0.0030) in ESCC patients than controls. However, a significant correlation was observed between plasma miR-19b levels and concentrations of red blood cells (P=0.0073) and haemoglobin (P=0.0072). (3) miR-25 expression was found to be significantly higher in ESCC tissues (P=0.0157) and ESCC cell lines (P=0.0093) than in normal tissues and fibroblasts. (4) In a large-scale validation analysis, plasma miR-25 levels were significantly higher in 105 preoperative (P<0.0001) ESCC patients who underwent curative oesophagectomy and 20 superficial ESCC patients who underwent endoscopic resection (P<0.0001) than in 50 healthy volunteers. (5) Plasma miR-25 levels were significantly reduced in postoperative samples than in preoperative samples (P<0.0005) and were significantly increased during ESCC recurrences (P=0.0145). Conclusions: Plasma miR-25 might be a clinically useful biomarker for cancer detection and the monitoring of tumour dynamics in ESCC patients.