Abstract B58: Functional analysis of the cell adhesion molecule Nectin-4 in the unique tumor microenvironment of ovarian cancer.

Abstract

Abstract A unique aspect of ovarian cancer progression is the collection of ascites fluid in the abdominal cavity, which contains free-floating tumor cells in the form of single cells and multicellular aggregates (spheroids). In previous studies, we showed that the cell adhesion molecule Nectin-4 is overexpressed in ovarian cancer tumors and that the soluble fragment of Nectin-4 (sN4) is detected in the ascites fluid and sera of ovarian cancer patients. The objectives of this study were to determine how Nectin-4 is cleaved from the surface of ovarian cancer cells and the functional role that Nectin-4 plays in the aggregation, invasion, and proliferation of ovarian cancer cells. Functional assays were conducted using human ovarian cancer cell lines that differed in their levels of expression of Nectin-4. First, NIH:OVCAR5 cells, which express moderate levels of Nectin-4, were either: (a) transfected with shRNA targeting Nectin-4 (resulting in almost complete knockdown of Nectin-4 expression) or (b) transfected with full length Nectin-4 to overexpress Nectin-4. Second, MA148 cells, which do not endogenously express Nectin-4 were transfected with a full length Nectin-4 cDNA. Cells that expressed high levels of Nectin-4 formed multicellular aggregates and proliferated more rapidly than cells in which Nectin-4 levels had been knocked down by shRNA. Nectin-4 knock down cells also migrated more slowly in a wound healing assay than cells transfected with a control shRNA. Cells that overexpressed Nectin-4 took a longer time to disaggregate and invade monolayers of mesothelial cells. In addition, cells that overexpressed Nectin-4 shed sN4 following 3 hours of stimulation with phorbol myristate acetate. A broad spectrum inhibitor of matrix metalloproteases and A Disintegrin And Metalloproteases (ADAMs) completely inhibited Nectin-4 shedding. Our results suggest that Nectin-4 promotes cell-cell adhesion (important in the formation of multicellular aggregates), yet it can be cleaved from the surface of cells to allow cells to disaggregate (important in invasion). Understanding the role of Nectin-4 in the multifaceted ovarian cancer tumor microenvironment is critical in order to facilitate its development as a novel therapeutic target for ovarian cancer. Citation Format: Kristin L.M. Boylan, Petra C. Buchanan, Dip Shukla, Melissa DeRycke, Bruce Walcheck, Amy P.N. Skubitz. Functional analysis of the cell adhesion molecule Nectin-4 in the unique tumor microenvironment of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B58.