MicroRNA expression alterations are linked to tumorigenesis and non-neoplastic processes in pancreatic ductal adenocarcinoma

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Abstract
Pancreatic ductal adenocarcinoma (PDAC) is known for its very poor overall prognosis. Accurate early diagnosis and new therapeutic modalities are therefore urgently needed. We used 377 feature microRNA (miRNA) arrays to investigate miRNA expression in normal pancreas, chronic pancreatitis, and PDAC tissues as well as PDAC-derived cell lines. A pancreatic miRNome was established comparing the data from normal pancreas with a reference set of 33 human tissues. The expression of miR-216 and -217 and lack of expression of miR-133a were identified as characteristic of pancreas tissue. Unsupervised clustering showed that the three pancreatic tissues types can be classified according to their respective miRNA expression profiles. We identified 26 miRNAs most prominently misregulated in PDAC and a relative quantitative reverse transcriptase-polymerase chain reaction index using only miR-217 and -196a was found to discriminate normal pancreas, chronic pancreatitis and cancerous tissues, establishing a potential utility for miRNAs in diagnostic procedures. Lastly, comparing differentially expressed genes from PDAC with predicted miRNA target genes for the top 26 miRNAs, we identified potential novel links between aberrant miRNA expression and known target genes relevant to PDAC biology. Our data provides novel insights into the miRNA-driven pathophysiological mechanisms involved in PDAC development and offers new candidate targets to be exploited both for diagnostic and therapeutic strategies.