Background: Cholangiocarcinoma is the second most frequent primary malignant tumor of the liver, accounting for 10-15% of all primary liver cancers. Cholangiocarcinoma grows at the expense of epithelial cells that line intra- and extra-hepatic bile ducts. The adaptor protein EBP50 (Ezrin-radixin-moesin Binding Phosphoprotein 50) binds and regulates transmembrane transporters and receptors including Epidermal Growth Factor Receptor (EGFR). EBP50 and EGFR are both expressed in the normal biliary epithelium. While EGFR participates in biliary carcinogenesis, implication of EBP50 in this cancer is unknown. The aim of the study was to determine the potential links between EBP50 and EGFR in human biliary carcinoma. Methods: In vitro studies were performed in the human biliary epithelial cell line, Mz-ChA-1, that retains epithelial phenotype and endogenous expression of EBP50 and EGFR. The role of EBP50 was examined using siRNA. Cell scattering and migration were evaluated using E-cadherin immunostaining and Boyden chamber, respectively. For in vivo study, 112 patients (mean age: 59.5±11 years, 55 females and 57 males) who underwent surgical resection for hilar (n=53) and peripheral (n=59) cholangiocarcinoma in one single institution were analyzed retrospectively. Immunohistochemistry on tissue microarrays was performed to assess EBP50 and EGFR expression. Results: EGF activates EGFR and the three main signaling pathways, ERK1/2, STAT3 and Akt, in Mz-ChA-1 biliary cancer cells. Inhibition of EBP50 in EGF-treated cells increases and maintains activation of EGFR, and of ERK1/2 and STAT3 but not Akt. Enhanced EGFR activation in response to EBP50 depletion confers sensitivity to EGFR tyrosine kinase inhibitor, gefitinib. Functionally, upon EGF, EGFR drives cell scattering by inducing disruption of adherens junctions. In addition, EGF activates formation of lamellipodia structures and therefore cell migration. Interestingly, inhibition of EBP50 in non EGF-stimulated cell has the same effects on cell scattering and migration as those observed with EGF alone. Cell dispersion due to EBP50 inhibition is abolished in the presence of gefitinib. Moreover, impact on cell scattering and migration is even greater when both EGF addition and EBP50 siRNA are combined. In vivo, delocalization of EBP50 normally expressed beneath the apical membrane is associated with EGFR expression in human biliary carcinoma tissues (p=0.002). Conclusion: These data provide evidence for an essential role of EBP50 in repressing EGFR-induced signaling pathway and migration. EBP50 at the membrane may be critical to confine cancer progression by preventing migration of biliary cancer cells.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5205.