Vitronectin and Its Receptors Partly Mediate Adhesion of Ovarian Cancer Cells to Peritoneal Mesothelium in vitro

Abstract

Epithelial ovarian cancer cells metastasize by implanting onto the peritoneal mesothelial surface of the abdominal cavity. Adhesive molecules that lead to this implantation remain unclear. The aim of our study was to focus on the role of vitronectin (Vn) and its receptors, α_v integrins and urokinase plasminogen activator receptor (uPAR), in the interactions of ovarian adenocarcinoma cells (IGROV1 and SKOV3 cell lines) with mesothelial cells (MeT-5A cell line and primary cultures). For all cell lines, immunofluorescence staining disclosed the presence of Vn over the whole cell surface and in thin continuous deposits underlining the cell periphery. Recruitment of Vn receptors to cell-cell contact sites was also revealed. We developed two distinct methods for the evaluation of in vitro cell-cell adhesion using cocultures of the tumor and mesothelial cells. Both adhesion assays revealed a strong ability of ovarian cancer cells to adhere preferentially to mesothelial intercellular junctions. Adhesion of ovarian carcinoma cells to mesothelial cells was significantly inhibited using anti-Vn-, -α_v-integrin- and -uPAR-blocking antibodies or cyclic peptide cRGDfV. These results evidence the ability of ovarian carcinoma cells to bind to peritoneal mesothelium in vitroand strongly suggest that Vn and its receptors contribute to this crucial event.

<em>In vitro</em> Mesothelial Clearance Assay that Models the Early Steps of Ovarian Cancer Metastasis

“…Previously, several groups [8][9][10][11][12][13][14] had used endpoint assays to show that ovarian cancer cells attach to and invade into mesothelial cell monolayers. This assay is unique in that it uses fluorescently labeled cells to distinguish tumor cells from mesothelial cells, so that the dynamics of these two cell populations can be monitored throughout the assay.…”

“…Our protocol was adapted from previously described methods for analyzing ovarian tumor cell interactions with mesothelial monolayers [8][9][10][11][12][13][14][15][16] , and was first described in a report showing that ovarian tumor cells utilize an integrin -dependent activation of myosin and traction force to promote the exclusion of the mesothelial cells from under a tumor spheroid 17 . This model takes advantage of time-lapse fluorescence microscopy to monitor the two cell populations in real time, providing spatial and temporal information on the interaction.…”

Mesenchymal gene program–expressing ovarian cancer spheroids exhibit enhanced mesothelial clearance

“…Ovarian cancer cells can attach and spread on multiple ECM proteins associated with the mesothelium and underlying basement membrane, including collagen I, collagen IV, laminin, vitronectin, and fibronectin; α and β integrins, as well as CD44, have been shown to serve as tumor cell receptors for these ligands (9,(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). While ovarian cancer cell adhesion and spreading on mesothelial monolayers has been well characterized, there has been much less focus on understanding the mechanisms associated with ovarian cancer cell invasion into and displacement of cells in the mesothelial monolayer.…”

WOMEN IN CANCER THEMATIC REVIEW: Ovarian cancer–peritoneal cell interactions promote extracellular matrix processing

“…Implantation and invasion occurs within a tumour-host interface where cancer and peritoneal cells exchange proteins and peptides, which modify the local ECM and promote metastasis (Gardner et al 1995, Strobel & Cannistra 1999, Freedman et al 2004, Ricciardelli & Rodgers 2006, Said et al 2007, Heyman et al 2008, Kenny et al 2008. Several ECM molecules have recently been identified to regulate the adhesion and invasion of ovarian cancer cells to peritoneal cells; however, an understanding of the cellular and molecular mechanisms involved are only just beginning to emerge (Gardner et al 1996, Freedman et al 2004, Heyman et al 2008, Kenny et al 2008. A greater understanding of these processes would potentially lead to the discovery of novel molecular targets to block this critical step of ovarian cancer metastasis.…”