Abstract A79: Plectin trafficking in oncosomes contributes to pancreatic cancer proliferation and invasion.

Abstract

Background and Aims: We recently showed that the aberrant extracellular localization of the cytoskeletal linker protein plectin is a biomarker for the progression of pancreatic ductal adenocarcinoma (PDAC), one of the most aggressive malignancies. In this study, we assess the molecular mechanism for plectin deregulation and its functional role in PDAC progression. Methods: To examine their potential contribution to aberrant extracellular localization of plectin, oncosomes (secreted membrane-derived microvesicles) produced by PDAC cells were collected by ultracentrifugation of PDAC-conditioned media and evaluated by immunoblotting. RT-PCR was used to define which plectin isoforms showed altered expression in PDAC compared to normal pancreatic ducts. Based on this information, we tested the impact of isoform-specific interacting proteins on plectin trafficking. Finally, we examined the impact of modulation of plectin on PDAC migration and invasion via transwell migration assay. Results: Plectin was localized on the cell surface as well as secreted through oncosomes in PDAC cell lines but not in non-transformed human pancreatic ductal epithelial (HPDE) cells. shRNA-mediated knockdown of integrin β4, a plectin 1a/1f interacting protein that were shown to be expressed in PDAC, impaired extracellular trafficking of plectin in PDAC cells. shRNA and overexpression studies collectively demonstrated a positive role of plectin proliferation, migration, and invasion of PDAC cells, and showed that plectin-positive oncosomes derived from PDAC are taken up by and induce migration and invasion in co cultured fibroblasts and endothelial cells. Conclusions: Plectin isoforms are differentially expressed in PDAC and are translocated to the cell surface in this cancer via oncosomes in an integrin β4-dependent manner. Plectin inactivation impairs PDAC cell proliferation, migration, and invasion of PDAC cells. Since cell surface plectin is a biomarker for transition of pre-invasive to invasive PDAC, these new insights into mechanisms of its deregulation will be important for the clinical development of plectin targeting diagnostic approaches. Our data also reveal unexpected direct functional roles for plectin in PDAC pathogenesis. Citation Format: Soo J. Shin, Jeffrey A. Smith, Gunther Rezniczek, Gerhard Wiche, Kimberly A. Kelly. Plectin trafficking in oncosomes contributes to pancreatic cancer proliferation and invasion. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Progress and Challenges; Jun 18-21, 2012; Lake Tahoe, NV. Philadelphia (PA): AACR; Cancer Res 2012;72(12 Suppl):Abstract nr A79.