Nuclear β-arrestin1 is a critical cofactor of hypoxia-inducible factor-1α signaling in endothelin-1-induced ovarian tumor progression.

Roberta Cianfrocca,Anna Bagnato,Rosanna Sestito,Laura Rosanò,Valeriana Di Castro,Valentina Caprara,Piera Tocci

doi:10.18632/oncotarget.7461

Abstract

Hypoxia-inducible factor-1α (HIF-1α) mediates the response to hypoxia or other stimuli, such as growth factors, including endothelin-1 (ET-1), to promote malignant progression in numerous tumors. The importance of cofactors that regulate HIF-1α signalling within tumor is not well understood. Here we elucidate that ET-1/ETA receptor (ETAR)-induced pathway physically and functionally couples the scaffold protein β-arrestin1 (β-arr1) to HIF-1α signalling. In epithelial ovarian cancer (EOC) cells, ET-1/ETAR axis induced vascular-endothelial growth factor (VEGF) expression through HIF-1α nuclear accumulation. In these cells, activation of ETAR by ET-1, by mimicking hypoxia, promoted the nuclear interaction between β-arr1 and HIF-1α and the recruitment of p300 acetyltransferase to hypoxia response elements on the target gene promoters, resulting in enhanced histone acetylation, and HIF-1α target gene transcription. Indeed, β-arr1-HIF-1α interaction regulated the enhanced expression and release of downstream targets, such as ET-1 and VEGF, required for tumor cell invasion and pro-angiogenic effects in endothelial cells. These effects were abrogated by β-arr1 or HIF-1α silencing or by pharmacological treatment with the dual ET-1 receptor antagonist macitentan. Interestingly, ETAR/β-arr1 promoted the self-amplifying HIF-1α-mediated transcription of ET-1 that sustained a regulatory circuit involved in invasive and angiogenic behaviors. In a murine orthotopic model of metastatic human EOC, treatment with macitentan, or silencing of β-arr1, inhibits intravasation and metastasis formation. Collectively, these findings reveal the interplay of β-arr1 with HIF-1α in the complexity of ET-1/ETAR signalling, mediating epigenetic modifications directly involved in the metastatic process, and suggest that targeting ET-1-dependent β-arr1/HIF-1α pathway by using macitentan may impair EOC progression.

Highlights

In epithelial ovarian cancer (EOC), the most lethal gynecological malignancy, the autocrine and paracrine loop mediated by the aberrant activation of the G protein coupled receptor (GPCR) endothelin A receptor (ETAR) by endothelin-1 (ET-1), elicits pleiotropic activities, including cell proliferation, survival, migration, epithelial mesenchymal transition (EMT), invadopodia formation, chemoresistance and neovascularization, through the activation of different signalling networks [1,2,3,4]
ET-1/ETA receptor (ETAR) induces vascular-endothelial growth factor (VEGF) release through HIF1α that is blocked by macitentan In EOC, VEGF has been reported to be a major mediator of ascites formation, invasiveness and metastatic dissemination, and is thereby associated with poor patient prognosis [33, 34]
After incubation with ET-1, VEGF transcript levels were stimulated to an extent comparable with that induced by hypoxia, a recognized potent stimulus of VEGF (Figure 1A)

Summary

Introduction

In epithelial ovarian cancer (EOC), the most lethal gynecological malignancy, the autocrine and paracrine loop mediated by the aberrant activation of the G protein coupled receptor (GPCR) endothelin A receptor (ETAR) by endothelin-1 (ET-1), elicits pleiotropic activities, including cell proliferation, survival, migration, epithelial mesenchymal transition (EMT), invadopodia formation, chemoresistance and neovascularization, through the activation of different signalling networks [1,2,3,4]. Atlas (TCGA) data confirmed that ETAR, and the miR30a that controls it, are associated with worse prognosis in high-grade serous ovarian cancers (HG-SOC) [6,7,8] In these cells ETBR appears to have tumor-promoting activity through evasion of immune response [1, 9], as well as angiogenic and lymphangiogenic responses on blood and lymphatic endothelial cells [10, 11]. The various functions of GPCR are often mediated by the ability of β-arrestin (β-arr1), ubiquitously expressed adaptor protein, to serve as signal transducer and scaffold molecule in different malignancies [1,2,3, 8, 12,13,14,15,16,17,18,19,20]. ETAR mediated nuclear β-arr recruitment might allow fine tuning of important signalling cascades, contributing to the overall tumoral response to ET-1 during metastatic progression

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