Abstract 698: β-arrestin-1 as nuclear signalling element essential for endothelin A receptor-induced epithelial to mesenchymal transition and chemoresistance

Abstract

Abstract The onset of chemoresistance is the major challenge in epithelial ovarian cancer (EOC). Emerging evidence suggests molecular and phenotypic association between chemoresistance and epithelial-mesenchymal transition (EMT) in cancer. We recently demonstrated that β-arrestin-1, scaffold and signaling protein of G-protein-coupled receptors, is recruited to endothelin A receptor (ETAR) to form molecular signaling complexes which concur to activate β-catenin transcriptional activity, EMT and metastasis. Here, by using biochemical and imaging techniques, we provide evidence that in EOC cells, ETAR activation by endothelin-1 (ET-1) induces nuclear translocation of β-arrestin-1 and its association with β-catenin. ChIP assays demonstrated that following this translocation, β-arrestin-1 was selectively enriched at specific promoters of β-catenin target genes, such as ET-1, MMP-2, cyclin D1. Further experiments showed that ET-1 promotes the nuclear association between histone acetyltransferase p300 and β-arrestin and the recruitment of p300 on these promoters, resulting in H3 and H4 histone acetylation and enhanced gene transcription. In chemoresistant EOC cells, ET-1/ETAR axis is overexpressed associated with EMT marker expression. Most importantly, the transcriptional activity of β-catenin was upregulated in chemoresistant EOC cells, associated with enhanced ETAR and β-arrestin-1 expression, providing molecular evidence that the ETAR/β-arrestin-1-mediated EMT signaling in EOC can represent a “salvage pathway” occurring during chemoresistance development. Interestingly, ETAR blockade with zibotentan, a specific ETAR antagonist, or its silencing with siRNA, abrogates both the engagement of β-arrestin-1 in the nucleus and the interplay between ET-1 and the β-catenin in controlling gene transcription. In vivo, zibotentan inhibited tumor growth of sensitive and resistant EOC xenografts, associated with reduction of EMT markers, and sensitized to chemotherapy. Analysis of EOC human tissues revealed that ETAR is overexpressed in resistant tumors and is associated with EMT phenotype. Our data provide the first evidence that blockade of ETAR/β-arrestin-1-driven EMT can overcome chemoresistance and inhibit tumor progression, improving the outcome of EOC patients’ treatment. Supported by AIRC Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 698. doi:10.1158/1538-7445.AM2011-698