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Research Mentor and Department
William Gillanders, M.D., Department of Surgery
Epithelial cell adhesion molecule (EpCAM) is a signaling molecule that is expressed at high levels in epithelial carcinoma cells. The purpose of this study is to better understand EpCAM interactions with itself in human epithelial carcinoma cell lines in order to determine how such interactions affect regulation of downstream cell-signaling pathways. A crystal structure has already been elucidated that shows the formation of a mutated recombinant EpCAM dimer between its extracellular domains. Using this crystal structure model, we hypothesized that EpCAM can form a dimer with itself in human cell lines. Chemical cross-linking experiments were performed under various reaction conditions to form not only dimers, but also trimers and tetramers. Using recombinant EpCAM proteins and 293T cells transfected with an EpCAM expression vector, we observed EpCAM form trimers and tetramers in addition to the expected dimers. However, in human epithelial cancer cell lines that have high expression of EpCAM, only EpCAM dimers were observed. Finally, we noticed that EpCAM oligomers formed more readily as the reaction environment became more basic. From these results, we can conclude that EpCAM forms dimers in cells, and EpCAM also interacts with itself to form oligomers. These interactions are strengthened in more basic conditions. These results provide evidence for investigating how such interactions affect regulation of downstream cell signaling pathways and tumor growth in epithelial cancers, especially breast cancer.