Factors Affecting the Expression of Carcinoembryonic Antigen at the Surface of Cultured Human Colon Carcinoma Cells

Factors affecting the expression of carcinoembryonic antigen (CEA) at the surface of in vitro human colon carcinoma cells were determined using 125I-labeled antibodies. Binding of specific anti-CEA antibodies resulted in polar redistribution of CEA, followed by endocytosis of most of the CEA-anti-CEA complexes. These processes were temperature and energy dependent. CEA removed from the tumor cell surface by antibody was totally replaced within 6 hr at 37 degrees, and the reexpression of CEA required protein synthesis. Examination of clonally derived subpopulations of various strains of human colon cancer cells indicated that control over the level of cell surface CEA expressed was genetically stable in vitro. CEA expression was enhanced in a low-CEA-producing strain by incorporating theophylline in the culture medium, and the inclusions of bromodeoxyuridine enhanced the expression of a high-CEA-producing strain. The kinetics of enhancement of CEA expression by these two drugs differed. These findings suggest that CEA expression may be controlled by more than a single gene function.