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 GCT in vitro.

CONTEXT: 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. OBJECTIVE: 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. DESIGN: 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. RESULTS: 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. CONCLUSIONS: These data suggest an autocrine role for VEGF in GCT and encourage clinical studies on anti-VEGF treatments in this disease.

Anti-Müllerian hormone inhibits growth of AMH type II receptor-positive human ovarian granulosa cell tumor cells by activating apoptosis.

Ovarian granulosa cell tumors (GCTs) are sex cord stromal tumors that constitute 3-5% of all ovarian cancers. GCTs usually present with an indolent course but there is a high risk of recurrence, which associates with increased mortality, and targeted treatments would be desirable. Anti-Müllerian hormone (AMH), a key factor regulating sexual differentiation of the reproductive organs, has been implicated as a growth inhibitor in ovarian cancer. GCTs and normal granulosa cells produce AMH, but its expression in large GCTs is usually downregulated. Further, as the lack of specific AMH-signaling pathway components leads to GCT development in mice, we hypothesized that AMH inhibits growth of GCTs. Utilizing a large panel of human GCT tissue samples, we found that AMH type I receptors (ALK2, ALK3 and ALK6) and type II receptor (AMHRII), as well as their downstream effectors Smad1/5, are expressed and active in GCTs. AMHRII expression was detected in the vast majority (96%) of GCTs and correlated with AMH mRNA and protein expression. AMH mRNA level was low in large GCTs, confirming previous findings on low-AMH protein expression in large human as well as mouse GCTs. To study the functional role of AMH in this peculiar ovarian cancer, we utilized a human GCT cell line (KGN) and 10 primary GCT cell cultures. We found that the AMH-Smad1/5-signaling pathway was active in these cells, and that exogenous AMH further activated Smad1/5 in KGN cells. Furthermore, AMH treatment reduced the number of KGN cells and primary GCT cells, with increasing amounts of AMH leading to augmented activation of caspase-3 and subsequent apoptosis. All in all, these data support the premise that AMH is a growth inhibitor of GCTs.