The high mortality of epithelial ovarian cancer (EOC) is mainly caused by resistance to the available therapies. In EOC, the endothelin-1 (ET-1, EDN1)–endothelin A receptor (ETAR, EDNRA) signaling axis regulates the epithelial–mesenchymal transition (EMT) and a chemoresistant phenotype. However, there is a paucity of knowledge about how ET-1 mediates drug resistance. Here, we define a novel bypass mechanism through which ETAR/β-arrestin-1 (β-arr1, ARRB1) links Wnt signaling to acquire chemoresistant and EMT phenotype. We found that ETAR/β-arr1 activity promoted nuclear complex with β-catenin and p300, resulting in histone acetylation, chromatin reorganization, and enhanced transcription of genes, such as ET-1, enhancing the network that sustains chemoresistance. Silencing of β-arr1 or pharmacologic treatment with the dual ETAR/ETBR antagonist macitentan prevented core complex formation and restored drug sensitivity, impairing the signaling pathways involved in cell survival, EMT, and invasion. In vivo macitentan treatment reduced tumor growth, vascularization, intravasation, and metastatic progression. The combination of macitentan and cisplatinum resulted in the potentiation of the cytotoxic effect, indicating that macitentan can enhance sensitivity to chemotherapy. Investigations in clinical specimens of chemoresistant EOC tissues confirmed increased recruitment of β-arr1 and β-catenin to ET-1 gene promoter. In these tissues, high expression of ETAR significantly associated with poor clinical outcome and chemoresistance. Collectively, our findings reveal the existence of a novel mechanism by which ETAR/β-arr1 signaling is integrated with the Wnt/β-catenin pathway to sustain chemoresistance in EOC, and they offer a solid rationale for clinical evaluation of macitentan in combination with chemotherapy to overcome chemoresistance in this setting. Cancer Res; 74(24); 7453–64. ©2014 AACR.

Despite the fundamental pathophysiological importance of β-catenin in tumor progression, the mechanism underlying its final transcriptional output has been partially elucidated. Here, we report that β-arrestin-1 (β-arr1) is an epigenetic regulator of endothelin (ET)-1-induced β-catenin signaling in epithelial ovarian cancer (EOC). In response to ET A receptor (ET_AR) activation by ET-1, β-arr1 increases its nuclear translocation and direct binding to β-catenin. This in turn enhanced β-catenin nuclear accumulation and transcriptional activity, which was prevented by expressing a mutant β-arr1 incapable of nuclear distribution. β-arr1–β-catenin interaction controls β-catenin target gene expressions, such as ET-1, Axin 2, Matrix metalloproteinase 2, and Cyclin D1, by promoting histone deacetylase 1 (HDAC1) dissociation and the recruitment of p300 acetyltransferase on these promoter genes, resulting in enhanced H3 and H4 histone acetylation, and gene transcription, required for cell migration, invasion and epithelial-to-mesenchymal transition. These effects are abrogated by β-arr1 silencing or by mutant β-arr1, as well as by β-catenin or p300 silencing, confirming that nuclear β-arr1 forms a functional complex capable of regulating epigenetic changes in β-catenin-driven invasive behavior. In a murine orthotopic model of metastatic human EOC, silencing of β-arr1 or mutant β-arr1 expression, as well as ET_AR blockade, inhibits metastasis. In human EOC tissues, β-arr1–β-catenin nuclear complexes are selectively enriched at β-catenin target gene promoters, correlating with tumor grade, confirming a direct in vivo β-arr1–β-catenin association at specific set of genes involved in EOC progression. Collectively, our study provides insights into how a β-arr1-mediated epigenetic mechanism controls β-catenin activity, unraveling new components required for its nuclear function in promoting metastasis.

In epithelial ovarian cancer (EOC), activation of endothelin-1 (ET-1)/endothelin A receptor (ETAR) signalling is linked to many tumor promoting effects, such as proliferation, angiogenesis, invasion and metastasis. These effects are dependent by the activation of critical signalling pathways, such as MAPK, Akt, and β-catenin, through specific cytosolic and nuclear scaffolding functions of β-arrestin 1 (β-arr1). Here, we have assessed the potential role of ET-1/ETAR in promoting NF-κB signalling in EOC cells through β-arr-1 recruitment. We used cultured HEY EOC cells cultured in the presence or absence of ET-1 and the ETAR antagonist BQ123. The phosphorylation of p65 and Iκ-Bα was evaluated by immunoblotting analysis. The interaction between p65 and β-arr1 was evaluated by immunoprecipitation experiments in nuclear extracts. NF-κB promoter activity was evaluated by transfection with NF-κB-driven luciferase reporter construct. Assessment of the function of β-arr1 was achieved by β-arr1 silencing with shRNA and expression of β-arr1-FLAG expression vector. In EOC cells, ET-1 promotes the phosphorylation of p65 subunit and the cytoplasmic inhibitor IκB that in turn led to increased NF-κB transcriptional activity. These effects were inhibited by the use of BQ123, as well as by β-arr-1 silencing, suggesting that ET-1 through ETAR promotes the recruitment of β-arr1 to regulate NF-κB signalling. Moreover, the nuclear physical interaction between p65 and β-arr1 indicates a nuclear function of β-arr-1 in ETAR-driven NF-κB transcriptional activity. Altogether these findings reveal a previously unrecognized pathway that depends on β-arr1 to sustain NF-κB signalling in response to ETAR activation in ovarian cancer.

The limited clinical response observed in high-grade serous ovarian cancer (HG-SOC) with high frequency of TP53 mutations (mutp53) might be related to mutp53-driven oncogenic pathway network. Here we show that β-arrestin1 (β-arr1), interacts with YAP, triggering its cytoplasmic-nuclear shuttling. This interaction allows β-arr1 to recruit mutp53 to the YAP-TEAD transcriptional complex upon activation of endothelin-1 receptors (ET-1R) in patient-derived HG-SOC cells and in cell lines bearing mutp53. In parallel, β-arr1 mediates the ET-1R-induced Trio/RhoA-dependent YAP nuclear accumulation. In the nucleus, ET-1 through β-arr1 orchestrates the tethering of YAP and mutp53 to YAP/mutp53 target gene promoters, including EDN1 that ensures persistent signals. Treatment of patient-derived xenografts reveals synergistic antitumoral and antimetastatic effects of the dual ET-1R antagonist macitentan in combination with cisplatinum, shutting-down the β-arr1-mediated YAP/mutp53 transcriptional programme. Furthermore, ET_AR/β-arr1/YAP gene signature correlates with a worst prognosis in HG-SOC. These findings support effective combinatorial treatment for repurposing the ET-1R antagonists in HG-SOC.

MiR-30a inhibits endothelin A receptor and chemoresistance in ovarian carcinoma