Chemotherapy is the preferred therapeutic approach for advanced epithelial ovarian cancer (EOC), but a successful long-term treatment is prevented by the development of drug resistance. In EOC cells, there are ample evidences supporting the role of the endothelin-1 (ET-1)/ ET A receptor (ETAR) signaling in invasive and drug-resistant cells. Moreover, in these cells ET-1/ETAR pathway promotes the epithelial-mesenchymal transition (EMT), a phenotype that is closely linked with the development of drug resistance and metastasis. To decipher ETAR signaling complexity in EMT and chemoresistance, we explored the role of β-arrestin-1 (β-arr1), a protein that mediates signals in response to receptor recruitment, as nuclear scaffold to control gene transcription in chemoresistant EOC cells. To this end we used cisplatin-sensitive EOC cell lines (A2780 and 2008) and their resistant variants. In chemoresistant cells, β-arr1 and ETAR were ovexpressed. In response to ETAR activation by ET-1, β-arr1 increases its nuclear translocation, and its interaction with transcription factors critically involved in EMT, such as β-catenin, Snail, and HIF-1α, and forms nuclear complexes capable to localize these transcription factors on the promoter regions of their target genes, such as ET-1, Axin2, matrix-metalloproteinase-2, and Cyclin D1. Moreover, β-arr1, by promoting the dissociation of transcriptional repressors, such as HDAC1, and the recruitment of transcriptional activator, such as p300 acetyltransferase, controls epigenetic modifications and gene transcription. These effects are abrogated by β-arr1 silencing or by expression of a mutant β-arr1 incapable of nuclear distribution, confirming that nuclear β-arr1 forms functional complex capable of regulating epigenetic changes in ET-1-driven invasive behaviour. At functional level, β-arr1 silencing or expression of mutant β-arr1, as well as ET-1 receptor blockade resulted in reduced cell invasion, and EMT determinant expression, as well as metastasis inhibition in sensitive and resistant EOC xenografts, providing evidence that blockade of ETAR/β-arr1-driven EMT can overcome chemoresistance and inhibit tumor progression. In human EOC tissues, β-arr1-dependent nuclear complexes are selectively enriched at target gene promoters, correlating with tumor grade, confirming a direct in vivo β-arr1 association at specific set of genes involved in EOC progression. Collectively, our findings provide insights into how β-arr1-mediated epigenetic mechanism driven by ETAR controls EMT transcriptional responses and chemoresistance. Supported by AIRC.

Citation Format: Laura Rosanò, Roberta Cianfrocca, Piera Tocci, Elisa Semprucci, Francesca Spinella, Valeriana Di Castro, Anna Bagnato. Endothelin-induced multifunctional complex regulates β-arrestin-1 nuclear activity to promote EMT in chemoresistant ovarian cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 756. doi:10.1158/1538-7445.AM2013-756