The aim of this study was to evaluate the role of endothelin-1 (ET-1) in the sensitivity of ovarian carcinoma to paclitaxel, one of the most common drugs used for the management of this tumour histotype. ET-1 is a powerful mitogenic peptide produced by ovarian carcinomas and it acts as an autocrine growth factor, selectively through ETA receptor (ETAR), which is predominantly expressed in this tumour. OVCA 433 and HEY, two ovarian carcinoma cell lines, which produce elevated amounts of ET-1 and express abundantly high-affinity ETARs, were used. As demonstrated by sub-G1 peak in DNA content histograms and terminal transferase deoxytidyl uridine end labelling assay, we found that paclitaxel induces cytotoxic effect through the activation of apoptosis in both cell lines. When the treatment with paclitaxel was performed in association with ET-1, paclitaxel-induced apoptosis was inhibited. In order to evaluate which ET-1 receptor mediated the effect of ET-1 on protection from paclitaxel-induced apoptosis, we performed experiments using two selective antagonists for ETAR (BQ-123) and for ETBR (BQ-788). We showed that ETAR blockade inhibits the ET-1-induced survival activity against paclitaxel-mediated apoptosis. However, no effect was observed on blocking ETBR with BQ-788. Our results establish a novel role for ET-1 in determining survival of ovarian carcinoma cells and suggest that pharmacological ETAR blockade using a specific ETAR antagonist may provide a novel approach to the treatment of ovarian carcinoma in combination therapy.

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