Aims: Endothelin A receptor (ET(A)R) and epidermal growth factor receptor (EGFR) cross-talk enhances the metastatic potential of epithelial ovarian cancer (EOC) cells activating different pathways, including β-catenin signalling. Here, we evaluated β-catenin as one of ET(A)R/EGFR downstream pathway in the invasive behaviour of EOC cells and their therapeutic potential to co-target ET(A)R and EGFR.
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 β-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 β-catenin at the residue Y654, its dissociation from E-cadherin complexes and the accumulation as an active form. This pool of Tyr-β-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 ET(A)R 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 β-catenin, especially when combined with gefitinib.
Significance: Altogether these findings provide additional support to the potential use of ET(A)R and EGFR blockade as a new therapeutic opportunity for EOC treatment.
Copyright © 2012 Elsevier Inc. All rights reserved.