The homotypic cell aggregation of a carcinoembryonic antigen (CEA) positive colon cancer cell line (Colo 205) was induced in vitro by interferon-γ (IFN-γ) treatment. Divalent cations were required for this aggregation, as it was inhibited by EDTA. The partial inhibition by cytochalasin B and the complete inhibition by a mixture of sodium azide and 2-deoxyglucose suggests that the aggregation requires the integrity of cytoskeleton and active metabolism. The expression of CEA was increased in the cytoplasm and on the membrane of Colo 205 by IFN-γ treatment. Furthermore, this aggregation was inhibited completely by anti-CEA monoclonal antibody (mAb) and partially by mAb against intercellular adhesion molecule-1. This in vitro study suggests that CEA molecule participates in the IFN-γ induced homotypic adhesion of some CEA positive cancer cells and that IFN-γ has an important role in the regulation of cell-cell interaction mediated by CEA molecule.
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