EGF/EGFR axis contributes to the progression of cholangiocarcinoma through the induction of an epithelial-mesenchymal transition

Abstract

Epithelial-mesenchymal transition (EMT) is a cellular process involved in cancer progression. The first step of EMT consists in the disruption of E-cadherin-mediated adherens junctions. Cholangiocarcinoma (CCA), a cancer with a poor prognosis due to local invasion and metastasis, displays EMT features. EGFR, a receptor tyrosine kinase, plays a major role in CCA progression. The aim of the study was to determine if EMT is induced by EGFR in CCA cells. In vivo, the expression of E-cadherin was analysed in CCA tumours of 100 patients and correlated with pathological features and EGFR expression, and in a xenograft model in mice treated with gefitinib, an inhibitor of EGFR. In vitro, the regulation of EMT by EGFR was investigated in CCA cell lines. In human CCA, a cytoplasmic localization of E-cadherin occurred in 50% of the tumours was associated with the peripheral type of CCA, tumour size, the presence of satellite nodules and EGFR overexpression. In xenografted tumours, E-cadherin displayed a cytoplasmic pattern whereas the treatment of mice with gefitinib restored the membranous expression of E-cadherin. In vitro, EGF induced scattering of CCA cells that resulted from the disruption of adherens junctions. Internalization and decreased expression of E-cadherin, as well as nuclear translocation of β-catenin, were observed in EGF-treated CCA cells. In these cells, EMT-transcription factors (i.e., Slug and Zeb-1) and mesenchymal markers (i.e., N-cadherin and α-SMA) were induced, favoring cell invasiveness through cytoskeleton remodeling. All these effects were inhibited by gefitinib. The EGF/EGFR axis triggers EMT in CCA cells highlighting the key role of this pathway in CCA progression.