Abstract 1082: Loss of desmoglein 2 promotes tumor growth and progression through the activation of Src and facilitates the internalization of EGFR in biliary tract carcinoma cells

Abstract

Abstract Understanding the molecular carcinogenesis pathways is critical to establish novel individualized molecular targeted therapies and finally to improve overall clinical outcomes of patients with a highly heterogeneous group of malignancies such as biliary tract cancers (BTCs). In this context, we investigated the patho-physiological roles of a desmosomal component, desmoglein 2 (Dsg2) and found that Dsg2 functions as a tumor suppressor protein in BTC, as Dsg2 loss induced a number of cellular biological activities including proliferation, motility, invasion, transendothelial migration in vitro and tumor growth and metastasis in vivo. Clinico-pathological analyses of BTC patients indicated that lower expression of Dsg2 is associated with a poor prognosis of patients as perineural and lymphatic invasion were highly increased in those patients. In addition, loss of Dsg2 showed a significant increase of EGFR clearance from the cell membrane in BTC cells and patients' tumor tissues. Those cells were significantly decreased in the EGF-driven activation of EGFR and highly resistant to the anti-EGFR antibody treatment. Src appears to be involved in the Dsg2-mediated clearance of EGFR, as this significantly blocked by the suppression of cSrc expression in Dsg2-depleted cells, possibly through the direct binding of Dsg2 preferentially with an inactive form of Src through its SH2 domain. Suppression of cSrc by Src inhibitors or siRNA dramatically reduced BTC tumor growth in vitro and in vivo. In comparison with the anti-EGFR antibody therapy, Src-targeted therapies produced consistent anti-tumor activities independent with the expression status of EGFR in the BTC tumors. In conclusion, targeting Src would be a promising therapeutic approach to patients with advanced BTC and potentially useful in overcoming resistance to current anti-EGFR therapies, although further clinical studies are essentially required to translate the current preclinical knowledge into clinical practice. Citation Format: Sang-Hyun Lee, Jeong-Ki Min. Loss of desmoglein 2 promotes tumor growth and progression through the activation of Src and facilitates the internalization of EGFR in biliary tract carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1082.