Gene regulation by antitumor miR-2045 p in 78 pancreatic ductal adenocarcinoma : the clinical 79 significance of direct RACGAP 1 regulation 80

Previously, we established a microRNA (miRNA) expression signature in pancreatic 90 ductal adenocarcinoma (PDAC) tissues using RNA sequencing and found significantly reduced 91 expression of miR-204-5p. Here, we aimed to investigate the functional significance of miR-204-5p 92 and to identify miR-204-5p target genes involved in PDAC pathogenesis. Cancer cell migration and 93 invasion were significantly inhibited by ectopic expression of miR-204-5p in PDAC cells. 94 Comprehensive gene expression analyses and in silico database searches revealed 25 putative targets 95 regulated by miR-204-5p in PDAC cells. Among these target genes, high expression levels of 96 RACGAP1, DHRS9, AP1S3, FOXC1, PRP11, RHBDL2 and MUC4 were significant predictors of a 97 poor prognosis of patients with PDAC. In this study, we focused on RACGAP1 (Rac GTPase98 activating protein 1) because its expression was most significantly predictive of PDAC pathogenesis 99 (overall survival rate: P = 0.0000548; disease-free survival rate: P = 0.0014). Overexpression of 100 RACGAP1 was detected in PDAC clinical specimens, and its expression enhanced the migration and 101 invasion of PDAC cells. Moreover, downstream genes affected by RACGAP1 (e.g., MMP28, CEP55, 102 CDK1, ANLN and S100A14) are involved in PDAC pathogenesis. Our strategy to identify antitumor 103 miRNAs and their target genes will help elucidate the molecular pathogenesis of PDAC. 104