Furthermore, we found a large number of differentially expressed piRNAs when comparing tumour cell lines (RWP1 and PL45) downregulated for PIWIL3 or PIWIL4 against IPMN samples (n = 94) or against human PDAC samples (n = 22) ( Supplementary Table S1). This evidence concerns the gene PIWIL4 and pancreatic intraductal papillary-mucinous neoplasm.