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Involvement of αvβ 3 integrin and disruption of endothelial fibronectin network during the adhesion of the human ovarian adenocarcinoma cell line IGROV1 on the human umbilical vein cell extracellular matrix

Like the majority of tumor cells, ovarian cancer cell growth is critically dependent on their neovascularization. Adhesion molecules and cellular events that lead to ovarian tumor cell interactions with endothelial extracellular matrix surrounding the vasculature are poorly identified. To understand the role of αvβ3 integrin and its ligand fibronectin in this process, we used in vitro coculture models with IGROV1 human ovarian adenocarcinoma cell line and human umbilical vein endothelial cells (HUVEC). Adhesion assays revealed a strong ability of IGROV1 cells to adhere to HUVEC‐ECM. αvβ3 is mainly implicated and seems to cooperate with α5β1 integrin in this event. Immunofluorescence staining revealed the presence of αvβ3 and α5β1 in IGROV1 cells adhering on HUVEC‐ECM at regions of cell sub‐stratum contacts. Furthermore, our data showed the absence of fibronectin staining in IGROV1 cells and the disruption of the HUVEC‐ECM fibrillar fibronectin network under IGROV1 cell influence. In situ experiments in ovarian neoplastic tissue corroborated the absence of fibronectin in the tumor and its strong detection in vasculature. These findings suggest the active participation of αvβ3 and α5β1 integrins and the reorganization of endothelial fibronectin during the adhesion of IGROV1 cells to HUVEC‐ECM whereas IGROV1 cells seem to be unable to synthesize fibronectin. Thus, fibronectin integrin receptors expressed by ovarian tumor cells and endothelial fibronectin may be of importance in ovarian carcinoma neovascularization and during tumor‐vasculature interactions. © 2002 Wiley‐Liss, Inc.