Abstract
Abstract Epithelial cell adhesion molecule (EpCAM) is highly expressed in advanced epithelial cancers and tumor-initiated cells (TICs), but its roles in cancer progression remain to be elucidated. Here, we showed that the extracellular domain of EpCAM (EpEX) could bind to EGFR through EGF-like domain I, and subsequently activated its downstream molecules, ERK1/2 and Akt. EGFR inhibitor and knockdown of EGFR by shRNA ablated EpEX-induced ERK1/2 phosphorylation. Regulated intramembrane proteolysis (RIP) of EpCAM was induced similarly by EpEX and EGF through EGFR-dependent activation of ERK pathway. MEK inhibitor, U0126, could abolish ADAM17 and PS2 phosphorylation induced by EpEX. EpAb2-6, an anti-EpEX neutralizing monoclonal antibody, inhibits EpEX-activated EGFR-PI3K-AKT pathway in detached colon cancer cells. Moreover, intracellular domain of EpCAM (EpICD), the product of RIP-induced cleavage of EpCAM, is necessary for nuclear accumulation of β-catenin, and their target gene expressions in vitro and in mouse xenograft models. We also found that an increase of nuclear EpICD observed in CRCs predicted metastasis and poor prognosis in CRC patients. Finally, in animal model studies, EpAb2-6 therapy exhibited an enhanced antitumor effect and markedly extended the survival time of mice with human colorectal cancer in metastatic and orthotopic models. These results demonstrate that EpEX works as a growth factor in activating EGFR-mediated signaling, and as a potential target for treatment of colon cancer. This research was supported by grants from Academia Sinica and Ministry of Science and Technology [MOST 104-0210-01-09-02,MOST 105-0210-01-13-01], and the National Science Council (NSC103-2321-B-001-064), Taiwan (to H-C Wu). Citation Format: Kang-Hao Liang, Jun-Kai Lai, I-I Kuan, Hsien-Cheng Tso, Han-Chung Wu. EpCAM/EpEX regulate tumor progression through EGFR signaling in colon cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 327. doi:10.1158/1538-7445.AM2017-327
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