VEGF induces ascites in ovarian cancer patients via increasing peritoneal permeability by downregulation of Claudin 5

Objective. To evaluate the role of VEGF-dependent Claudin 5 production for the development of ascites via influencing endothelial permeability in peritoneal tissue of ovarian cancer patients. Methods. This study investigates the mechanisms of formation of ascites in ovarian cancer patients, performing RT-PCR, VEGF-ELISA and immunohistochemical dual staining for CD31 and Claudin 5. In addition, in order to analyze the connectivity of VEGF, Claudin 5, and endothelial permeability, an endothelial cell/ovarian cancer cell-co-culture-system was established and evaluated performing Western blot analysis and a permeability assay. Results. Firstly, VEGF-gene expression was demonstrated for all ovarian cancer and peritoneal biopsies. In addition, quantification of VEGF in the serum and ascites of ovarian cancer patients revealed significantly increased values. We subsequently demonstrated Claudin 5 production in the peritoneal vessels, which was weaker than in the vessels of the controls. Evaluation of endothelial permeability finally showed a VEGF-dependent regulation via Claudin 5 suggesting a mechanism for the development of ascites in ovarian cancer patients. Conclusion. VEGF induces ascites in ovarian cancer patients. This instance happens due to increased peritoneal permeability, caused by downregulation of the tight junction protein Claudin 5 in the peritoneal endothelium. (C) 2012 Elsevier Inc. All rights reserved.