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Epithelial cell adhesion molecule fragments and signaling in primary human liver cells
Author(s) -
Gerlach Jörg C.,
Foka Hubert G.,
Thompson Robert L.,
Gridelli Bruno,
Schmelzer Eva
Publication year - 2018
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.26286
Subject(s) - epithelial cell adhesion molecule , microbiology and biotechnology , intracellular , cell growth , cell , biology , gene knockdown , cell adhesion molecule , cell culture , extracellular , liver cell , chemistry , biochemistry , medicine , genetics
Epithelial Cell Adhesion Molecule (EpCAM), or CD326, is a trans‐membrane glycoprotein expressed by multiple normal epithelia as well as carcinoma. Human hepatic stem cells and bile duct epithelium of the liver are EpCAM positive. In tumor cell lines, its intracellular domain can be released after cleavage of the extracellular domain. Within the cell nucleus, it induces cell proliferation, but cleavage depends on cell contact. Fragments of various lengths have been described in tumor cells. Despite its described important role in proliferation in tumor cells, there is not much known about the expression and role of EpCAM fragments in primary human liver cells. Here, we demonstrate that EpCAM protein fragments and function are considerable different between tumor cells, normal fetal and adult liver cells. Contrary to previously reported findings in tumor cells, gene knockdown or treatment with an inhibitor of the cleavage enzyme ADAM17 (TACE) rather increased cell numbers in primary human fetal liver‐derived EpCAM‐positive cells. EpCAM fragment sizes were not affected by treatment with inhibitor. Knockdown of EPCAM gene expression by siRNA in sorted cells did not significantly affect proliferation‐associated genes or cell numbers. The intracellular domain could not be detected within cell nuclei of fetal and adult liver cells. In conclusion, signaling through the intracellular domain of EpCAM appears to be a mechanism that induces proliferation specifically in tumorigenic cells but not in normal primary EpCAM‐positive liver cells.