Circular RNA ADAM9 facilitates the malignant behaviours of pancreatic cancer by sponging miR-217 and upregulating PRSS3 expression.

Pancreatic cancer (PC) is a highly lethal human cancer. We previously found that Serine protease 3 (PRSS3), as an oncogene, is significantly upregulated in PC. In this study, we aimed to investigate the potential mechanism of PRSS3 dysregulation in PC. In this research, low miR-217 and high circ-ADAM9 expression were found in PC tissues and cell lines, which was closely associated with advanced clinical stage and lymph node metastasis. Patients with low miR-217 or high circ-ADAM9 expression had shorter survival time than those with high miR-217 or low circ-ADAM9 expression. Functionally, manipulation of miR-217 and circ-ADAM9 expression showed opposite effects on cell proliferation, migration and invasion. Stepwise mechanism studies indicated that circ-ADAM9 alleviated the inhibitory effect of miR-217 on PRSS3 by directly sponging miR-217 to increase the expression level of PRSS3, resulting in the activation of ERK/VEGF signalling pathway. In vivo, circ-ADAM9 silencing or miR-217 overexpression evidently retarded the growth of tumour, and the combination of them exhibited an additive inhibitory effect on tumourigenicity. Briefly, the ceRNA regulatory network of circ-ADAM9/miR-217/PRSS3 plays a pivotal role in PC progression by the regulation of ERK/VEGF signalling pathway.