The endothelin A receptor and epidermal growth factor receptor signaling converge on β-catenin to promote ovarian cancer metastasis

Aims: Endothelin A receptor (ETAR) and epidermal growth factor receptor (EGFR) cross-talk enhances the metastatic potential of epithelial ovarian cancer (EOC) cells activating different pathways, including beta-catenin signalling. Here, we evaluated beta-catenin as one of ETAR/EGFR downstream pathway in the invasive behaviour of EOC cells and their therapeutic potential to co-target ETAR and EGER. Main methods: The phosphorylation status and interactions of different proteins were analysed by immunoblotting and immunoprecipitation. Reporter activity and RT-PCR was used for evaluation of beta-catenin transcriptional activity and gene expression. Functional effects were evaluated by gelatin zymography and cell invasion assays. An orthotopic model of metastatic human EOC in mice was used for in vivo studies. Key findings: In EOC cell lines, ET-1 induced Src-dependent EGFR transactivation, causing tyrosine (Y) phosphorylation of beta-catenin at the residue Y654, its dissociation from E-cadherin complexes and the accumulation as an active form. This pool of Tyr-beta-catenin relocalised to the nucleus promoting its transcriptional activity, and the expression of its target genes, such as MMP-2. At functional level, ET-1 and EGFR circuits enhanced protease activity and cell invasion. All these effects were significantly inhibited by the ETAR antagonist, zibotentan, or EGFR inhibitor, gefitinib, and are completely blocked by co-addition of both drugs. In vivo, zibotentan treatment significantly inhibited metastases, associated with reduced expression and activation of MMPs and active beta-catenin, especially when combined with gefitinib. Significance: Altogether these findings provide additional support to the potential use of ETAR and EGFR blockade as a new therapeutic opportunity for EOC treatment. (c) 2012 Elsevier Inc. All rights reserved.