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

Abstract

Background and AimsPrecise 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. MethodsExosomes 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 (qRT-PCR). Changes in serum Ex-miR levels were assessed in two patients with PDAC who underwent curative resection. In situ hybridization (ISH) was performed to directly visualize PDAC-specific miR expression in cancer cells. ResultsWe 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 two patients with relatively early disease stages declined after curative resection. ISH demonstrated that Ex-miR-4516 expression exclusively occurred in cancer cells. ConclusionsLiquid 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.