Exosomal miRNA signature of pancreatic cyst: Liquid biopsies as indicators of pancreatic cancer.

Abstract

225 Background: Pancreatic cysts are a group of lesions with malignant potential. Currently, there are no consistently reliable biomarkers or imaging modalities to accurately predict biologic behavior of these cysts. We tested the hypothesis that tumor-derived exosomes (better conserved than free miRNA) can be acquired endoscopically from pancreatic cyst fluid and may allow for improved distinction between benign, premalignant and malignant cysts. Methods: Exosomes were isolated and characterised by differential and buoyant centrifugation from pancreatic cyst fluid obtained from 30 patients with pseudocysts (PS), serous cystic (SC), mucinous cysts (MC), intraductal papillary mucinous neoplasms (IPMN), pancreatitis (PA), and pancreatic cancer (PC) , confirmed with imaging and histology. An Illumina TruSeq Small RNA kit was used to construct a small RNA library, and the libraries were sequenced using the Illumina NextSeq 500 platform. The resulting sequencing FASTQ files were analyzed using miRDeep2 to identify both known and novel miRNAs. Results: Four significant miRNAs which are shared between six of the analyses, specifically hsa-miR-199b-3p, hsa-miR-199a-2-3p, hsa-miR-199a-1-3p and hsa-let-7i-5p were identified. MiRNA hsa-miR-27a-3p was significant and shared between five of the analyses. A total of 15, 12 and 2 significant miRNAs were shared between four, three and two of the analyses, respectively. Importantly, there were a total of 10 significant miRNAs which were unique to each analysis, with the exception of IPMN vs Pseudocyst, and Pancreatic cancer vs Pancreatitis. Specifically these unique miRNAs for each analysis are: hsa-miR-92a-2-3p (Pancreatitis vs Pseudocyst); hsa-miR-92a-1-3p (Serous vs Pseudocyst); hsa-miR-30e-5p (Pancreatic cancer vs Serous), hsa-miR-30b-5p (IPMN vs Pancreatic cancer); and hsa-miR-23b-3p, hsa-miR-99b-5p, hsa-miR-222-3p, hsa-miR-31-5p, hsa-miR-151a-5p, hsa-miR-221-3p (Pancreatic cancer vs. Pseudocyst). Conclusions: Exosomal miRNAs in pancreatic fluid may be used as a biomarker to differentiate between various cyst types and pancreatic cancer. A larger cohort with miRNA quantification and is needed to further validate these findings .