Although endothelin-1 (ET-1) and the endothelin A receptor (ETAR) regulate different steps of ovarian tumor progression, the molecular mechanism controlling the expression of ET-1 in this tumor is unknown. We previously demonstrated that ET-1 activates β-catenin/TCF4 transcriptional activity to promote cell invasion and metastasis. Here, we show that ET-1 gene is directly regulated by β-catenin in ovarian cancer cells. Thus, inhibition of β-catenin signalling results in lowered ET-1 promoter activity and expression, while enhanced β-catenin signalling leads to further activation of this gene. Chromatin immunoprecipitation (ChIP) demonstrated that, after ET-1 stimulus, β-catenin and its cognate DNA binding partner, TCF4, are recruited on the specific DNA element within the ET-1 promoter. Unravelling the role of the scaffold protein β-arrestin-1 as nucleus chaperone controlling β-catenin transcription activity, we demonstrated that β-arrestin-1 is required for the activation of ET-1 promoter, and for the recruitment of β-catenin/TCF4 on this promoter. In agreement with these findings, immunoprecipitation assay demonstrated that ET-1 promotes the interaction between endogenous β-catenin and β-arrestin-1 both in the cytoplasm and in the nucleus. Moreover, β-arrestin-1 siRNA leads to the loss of ET-1 mRNA expression and ET-1 secretion, as well as a significant inhibition of ET-1 promoter activity, thus suggesting the critical role of β-arrestin-1 in the β-catenin-dependent ET-1 gene expression. Further experiments showed that ET-1 promotes the nuclear association between histone acetyltransferase p300 and β-arrestin and the recruitment of p300 on the ET-1 promoter, resulting in H3 and H4 histone acetylation and enhanced ET-1 transcription. Besides ET-1, β-arrestin-1 represents a platform for achieving signal specificity that converges on β-catenin-mediated transcription of defined genes, such as cyclin D1 and matrix metalloprotease (MMP)-2, but not MMP-9. Moreover, ETAR blockade with the specific ETAR antagonist, zibontentan (ZD4054), abrogates both the engagement of β-arrestin and the interplay between ET-1 and the β-catenin in controlling gene transcription. In an intraperitoneal model of ovarian cancer metastasis, HEY cells expressing the mutant β-arrestin-1, or treatment with zibontentan, significantly reduced peritoneal tumor-cell dissemination and β-catenin expression, highlighting the importance of β-arrestin-mediated signaling in metastasis formation. Altogether these results reveal a positive inter-regulation between β-catenin and ET-1 that amplify the ET-1/ETAR autocrine loop in ovarian cancer cells, in which β-arrestin-1 acts as a nuclear messenger mediating epigenetic mechanism in β-catenin-mediated ET-1 transcription. Supported by AIRC, AstraZeneca

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2363.