Does VEGF facilitate local tumor growth and spread into the abdominal cavity by suppressing endothelial cell adhesion, thus increasing vascular peritoneal permeability followed by ascites production in ovarian cancer?

Abstract

BackgroundOvarian cancer is mostly associated with pathologically regulated permeability of peritoneal vessels, leading to ascites. Here, we investigated the molecular regulation of endothelial permeability by the vascular endothelial growth factor (VEGF) and both tight and adherens junction proteins (VE-cadherin and claudin 5) with regards to the tumor biology of different ovarian cancer types.MethodsSerum and ascites samples before and after surgery, as well as peritoneal biopsies of 68 ovarian cancer patients and 20 healthy controls were collected. In serum and ascites VEGF protein was measured by ELISA. In peritoneal biopsies co-localization of VE-cadherin and claudin 5 was investigated using immunohistochemical dual staining. In addition, the gene expression of VE-cadherin and claudin 5 was quantified by Real-time PCR. Differences in VEGF levels, VE-cadherin and claudin 5 gene expression were analyzed in relation to various tumor characteristics (tumor stage, grading, histological subtypes, resection status after surgery) and then compared to controls. Furthermore, human primary ovarian cancer cells were co-cultured with human umbilical vein endothelial cells (HUVEC) and changes in VE-cadherin and claudin 5 were investigated after VEGF inhibition.ResultsVEGF was significantly increased in tumor patients in comparison to controls and accumulates in ascites. The highest VEGF levels were found in patients diagnosed with advanced tumor stages, with tumors of poor differentiation, or in the group of solid / cystic-solid tumors. Patients with residual tumor after operation showed significantly higher levels of VEGF both before and after surgery as compared to tumor-free resected patients. Results of an immunohistochemical double-staining experiment indicated co-localization of VE-cadherin and claudin 5 in the peritoneal vasculature. Compared to controls, expression of VE-cadherin and claudin 5 was significantly suppressed in peritoneal vessels of tumor patients, but there were no significant differences regarding VE-cadherin and claudin 5 expression in relation to different tumor characteristics. A significant positive correlation was found between VE-cadherin and claudin 5 expression. VEGF inhibition in vitro was associated with significant increase in VE-cadherin and claudin 5.ConclusionsOur results indicate that increased peritoneal permeability in ovarian cancer is due to down-regulation of adhesion proteins via tumor derived VEGF. Advanced ovarian cancer with aggressive tumor biology may be associated with early dysregulation of vascular permeability leading to ascites. These patients may benefit from therapeutic VEGF inhibition.

Nectin‐2 in ovarian cancer: How is it expressed and what might be its functional role?

“…In the current study, we found Nectin‐2 localized in the peritoneal vasculature. This is in line with the results of our previous studies where colocalization of the adhesion proteins claudin 5 and VE‐cadherin, as well as decreased expression in the peritoneum of ovarian cancer patients, was found . In the current experiment, Nectin‐2 was clearly suppressed in the peritoneal endothelium of tumor patients as compared to controls, associated with highly expressed VEGF in the tumor and increased VEGF serum levels indicating that Nectin‐2 downregulation might be VEGF driven.…”

“…In our previous investigations, we showed that increased peritoneal vascular permeability is due to VEGF‐induced suppression of adhesion molecules in the peritoneal vasculature . Furthermore, we showed that VEGF‐derived ascites formation increases with aggressive ovarian cancer subtypes . In the current study, we found Nectin‐2 localized in the peritoneal vasculature.…”

“…24 Furthermore, we showed that VEGF-derived ascites formation increases with aggressive ovarian cancer subtypes. 29 In the current study, we found Nectin-2 localized in the peritoneal vasculature. This is in line with the results of our previous studies where colocalization of the adhesion proteins claudin 5 and VE-cadherin, as well as decreased expression in the peritoneum of ovarian cancer patients, was found.…”

“…27 Recent studies have indicated that for local tumor spread into the abdominal cavity and to the peritoneal tissue, tumor cell migration and adhesion are the main mechanisms involved. 29 Although very few studies are available, molecules such as Nectins are described to be involved in these processes. 8,17 These functions of Nectins implicate its possible roles in tumor cell survival and proliferation.…”

Recommendations for biomarker testing in epithelial ovarian cancer: a National Consensus Statement by the Spanish Society of Pathology and the Spanish Society of Medical Oncology

“…Elevated VEGF levels are related to greater vascular permeability and increased tendency towards peritoneal progression and ascites [70]. A meta-analysis including over 1000 ovarian cancer patients confirmed that elevated serum VEGF levels were associated with shorter progression-free survival (HR 2.46; 95% CI 1.84-3.29) and lower overall survival (HR 2.21; 95% CI 1.57-3.13) compared with low levels.…”