f missing the chance for a curative procedure in patients who are suitable for pancreatic surgical MiRNAs in Benign vs. Malignant Pancreatic Tumors resection can be devastating. BCT are divided into nonmucinous and mucinous variants: serous PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22189660 microcystic adenomas, which are non-mucinous tumors, have a very lowmalignant potential and very rarely progress to PDAC; intraductal papillary mucinous neoplasms are mucinous tumors that are connected to the native pancreatic ducts ; whilst the mucinous cystic neoplasms are separate from the ductal system. Main branch IPMN lesions carry the highest malignant potential, ranging between 57 to 92% and side-branch IPMN between 6 to 46%. MCNs have a high-malignant potential ranging from 6 to 36%. Out of the BCT, the most often encountered are the SMCA, MCNs, and IPMNs . The latter have more potential to give rise to in situ or invasive PDAC, via an adenoma-carcinoma sequence. Invasive malignancy arising on the background of an IPMN is termed Carcinoma-Ex-IPMN and is more common in main pancreatic duct IPMN. A correct preoperative diagnosis and evaluation of pancreatic BCT is crucial for clinical decision-making to sieve out those tumors that are already malignant or have a high-risk of malignant potential for which urgent surgical intervention is required. MiRNAs are a recently recognized class of non-coding short RNAs from 17 to 25 nucleotides in length that play a role in posttranscriptional gene regulation. Expression profiles of human miRNAs have demonstrated that many miRNAs are deregulated in cancer and these profiles will help further establish molecular diagnosis, prognosis and therapy. Several studies have demonstrated a different miRNA expression profile in PDAC compared to normal tissues. However, the profiles of miRNA production in PDAC precursor lesions remain largely unknown. In this report, miRNA expression signatures in low and highrisk pre-malignant pancreatic BCT were investigated. Furthermore, the role of oncogene targeting miRNAs in the regulation of malignant transformation from BCT was assessed and KRAS was identified as a direct target of miR-126. Ultimately, identification of miRNA markers for the clinical differentiation of these premalignant BCT would allow for early surgical resection to improve outcomes. 3 hours before being frozen at 280uC. The immunohistochemical analysis was performed on FFPE samples: normal pancreas n = 12, PDAC n = 12 and SMCA n = 12. Further detailed clinicopathological information about the patients is provided in Cell culture and transfection PANC-1 and MIA PaCa-2 pancreatic cells were purchased from the European Collection of Cell Cultures. Both were maintained in 50% DMEM and 50% RPMI supplemented with 10% FCS, 1% penicillin/streptomycin, and 1% glutamine. When the cells were ready for transfection, they were plated in 6 well plate the day before and then transfected with precursor miRNA or miRNA inhibitor for 48 hours using HiPerFect Transfection Reagent before lysis, RNA and protein extraction. RNA Isolation FFPE samples were deparaffinized with xylene and total RNA was collected using the miRNeasy Mini Kit according to the manufacturer’s instructions. Fresh tissue stored in MedChemExpress 80321-63-7 RNALater was crushed in liquid nitrogen and subsequent powder lysed in Trizol Reagent, followed by RNA isolation according to the manufacturer’s instructions. miRNA Microarray The microarray we used is applicable and has been validated for FFPE samples. Total RNA 
was extracted
