Serum Vascular Endothelial Growth Factor A (VEGF) Is Elevated in Patients with Ovarian Granulosa Cell Tumor (GCT), and VEGF Inhibition by Bevacizumab Induces Apoptosis in GCTin Vitro

Abstract

Ovarian granulosa cell tumors (GCT) are highly vascularized and express vascular endothelial growth factor A (VEGF) and its functional receptor VEGF receptor 2 (VEGFR-2). Angiogenesis inhibitors have been used in the treatment of ovarian carcinomas, whereas their roles in GCT remain unknown. The aim was to assess serum levels of VEGF and endostatin, an endogenous angiogenesis inhibitor, in GCT patients and to study the effect of bevacizumab (BVZ), a VEGF-binding monoclonal antibody, on human GCT cells in vitro. Using ELISA, we measured soluble VEGF and endostatin in the sera of 54 GCT patients and in conditioned media from cultures of 14 primary GCT and an established GCT cell line (KGN). The expression of activated VEGFR-2 was analyzed in GCT tissues using immunohistochemistry. GCT cells were treated with BVZ and analyzed for cell number and apoptosis. Serum VEGF was elevated in GCT patients, and the levels significantly decreased after tumor removal (P < 0.05), whereas serum endostatin levels changed conversely. Human GCT expressed activated VEGFR-2 protein, and the level of expression was associated with tumor VEGF and vascularization. In addition, the cultured GCT cells produced significant amounts of VEGF but not endostatin. Treatment of KGN cells with BVZ significantly reduced the number of viable cells by 41% and induced a 3.3-fold increase in apoptosis. Furthermore, BVZ induced a mean 2.6-fold increase in apoptosis in six primary GCT cell cultures studied. These data suggest an autocrine role for VEGF in GCT and encourage clinical studies on anti-VEGF treatments in this disease.