Endothelin-1 (ET-1) is present at high concentrations in ovarian cancer ascites and is overexpressed in primary and metastatic ovarian carcinomas. In these tumours the presence of ET-1 is associated with enhanced neovascularization and with vascular endothelial growth factor (VEGF) expression. In these tumour cells, ET-1 acts as an autocrine growth factor selectively through the receptor ETA, which is predominantly expressed in tumour cells. Furthermore, ET-1 produced by ovarian tumour cells stimulates VEGF production and VEGF-mediated angiogenic effects through ETA binding. These results demonstrate that activation of the ETA in ovarian carcinoma cells promotes cell proliferation, neovascularization and invasion, which are the principal hallmarks of malignant transformation. The present study was designed to investigate the effects of the ETA-selective antagonist ABT-627 on the ET-1-induced mitogenic effect in both primary cultures (PMOV1 and PMOV2) and cell lines (OVCA 433 and HEY) of ovarian carcinoma. All tumour cells express the components of the ET-1 system and secrete ET-1. ETA blockade by ABT-627 inhibits ET-1-induced mitogenic effects. The ETB antagonist BQ-788 is ineffective although all cell lines express both ETA and ETB mRNAs. In conclusion, our results demonstrate that ABT-627 is capable of inhibiting the proliferative activity of ET-1, suggesting that this potent ETA antagonist may provide a novel approach to the multidisciplinary treatment of ovarian carcinoma.

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