Increased Expression of the Large GTPase Dynamin 2 Potentiates Metastatic Migration and Invasion of Pancreatic Ductal Carcinoma

Pancreatic ductal tumors invade local parenchyma and metastasize to distant organs. Src-mediated tyrosine kinase signaling pathways promote pancreatic ductal adenocarcinoma (PDAC) metastasis, though the molecular mechanisms supporting this invasive process are poorly understood and represent important and novel therapeutic targets. The large GTPase Dynamin2 (Dyn2), a Src-kinase substrate, regulates membrane-cytoskeletal dynamics although it is yet to be defined if this mechanoenzyme contributes to tumor cell migration and invasion. Therefore the goal of this study was to test if Dyn2 is upregulated in human pancreatic tumors and to define its role in cell migration and metastatic invasion using in vitro assays and nude mouse models. Histological analysis showed that 81% of the 85 patients tested had elevated Dyn2 in PDAC tissue. To test if Dyn2 overexpression alters metastatic properties of human pancreatic tumor cells, stable clones of BxPC-3 cells overexpressing either wild-type Dyn2 or a phosphorylation-deficient mutant Dyn2Y(231/597)F known to attenuate Dyn2 function, were generated and analyzed for migratory capacity. Importantly, tumor cells expressing 2-3 fold levels of Dyn2 protruded lamellipodia at twice the rate, migrated faster (180%) and farther (2.5-fold greater net distance) on glass and through transwell chambers (2-3 fold more cells through the filter) compared to cells expressing Dyn2Y(231/597)F or vector alone. Further, siRNA-mediated depletion of Dyn2 and dynamin inhibitors MiTMAB and Dynasore significantly reduced cell migration (>66%), wound healing (>75%) and invasion in transwell assays (>95%) compared to DMSO treated cells. To test the metastatic potential conferred by increased Dyn2 expression, the BxPC-3 clonal cell lines were implanted orthotopically into the pancreas of nude mice. Cells expressing Dyn2-GFP exhibited a 3-fold increase in large distal tumors compared to cells expressing Dyn2Y(231/597)F or vector alone. Finally, histological analysis of pancreatic metastases from human patients revealed that Dyn2 is upregulated in 60% of metastatic tumors examined. These findings are the first to implicate dynamin in any neoplastic condition and to directly demonstrate a role for this mechanoenzyme in invasive cell migration.