Pancreatic Juice-Derived microRNA-4516 and microRNA-4674 as Novel Biomarkers for Pancreatic Ductal Adenocarcinoma.

Background And Aims: Precise diagnostic biomarkers are urgently required for pancreatic ductal adenocarcinoma (PDAC). Therefore, the aim of this study was to identify PDAC-specific exosomal microRNAs (Ex-miRs) from pancreatic juice (PJ) and evaluate their diagnostic potential.

Methods: Exosomes in PJ and serum were extracted using ultracentrifugation and confirmed morphologically and biochemically. PDAC-specific Ex-miRs were identified using our original miR arrays, in which "Ex-miRs derived from the PJ of patients with chronic pancreatitis (CP)" were subtracted from Ex-miRs commonly expressed in both "human PDAC cell lines" and "the PJ of patients with PDAC." We verified the expression of these miRs using quantitative real-time reverse transcription polymerase chain reaction. Changes in serum Ex-miR levels were assessed in 2 patients with PDAC who underwent curative resection. In situ hybridization was performed to directly visualize PDAC-specific miR expression in cancer cells.

Results: We identified novel Ex-miR-4516 and Ex-miR-4674 from the PJ of patients with PDAC, and they showed 80.0% and 81.8% sensitivity, 80.8% and 73.3% specificity, and 90.9% and 80.8% accuracy, respectively. The sensitivity, specificity, and accuracy of a triple assay of Ex-miR-4516/4674/PJ cytology increased to 93.3%, 81.8%, and 88.5%, respectively. In serum samples (n = 88), the sensitivity, specificity, and accuracy of Ex-miR-4516 were 97.5%, 34.3%, and 68%, respectively. Presurgical levels of serum-derived Ex-miR-4516 in 2 patients with relatively early disease stages declined after curative resection. In situ hybridization demonstrated that Ex-miR-4516 expression exclusively occurred in cancer cells.

Conclusion: Liquid assays using the in situ-proven Ex-miR-4516 may have a high potential for detecting relatively early-stage PDAC and monitoring its clinical course.