Flow cytometric identification of cell surface markers on cultured human colonic cell lines using monoclonal antibodies

The expression of tumor-associated cell surface antigens is a reflection of the state of cell differentiation of tumor cells in culture.Monoclonal antibodies (MoAbs) against the tumor-associated antigens carcinoembryonic antigen (CEA) and CA19-9 and the extracellular matrix protein CD44 were used to label the cell surface of human colonic cells in culture. The binding of each antibody to its respective antigen was measured by fluorescence-activated flow cytometry and expressed as a percentage of positive cells.The human colon adenocarcinoma cell (HCAC) line, LS-180, showed strong binding with CEA (81%), CA 19-9 (87%), and CD44 (83%). LS-174t cells, a trypsinized variant of LS-180 cells, showed less binding with CEA (66%) and CA 19-9 (49%), but no binding with CD44. With cells from HCAC line HT-29, antigen expression was highly variable for CEA (13% +/- 18) and CD44 (31% +/- 35) but was consistently positive for CA19-9 (33% +/- 13). The expression of CEA in the Caco-2 cell line was weak (24%), whereas there was no expression of CA19-9 and CD44. Normal human colon fibroblast cells (CCD-18Co) did not recognize the monoclonal antibodies to CEA or CA 19-9, but were strongly positive with the CD44 antibody (97%).These results support the concept that the expression of the tumor associated markers CEA and CA19-9 and the cell surface marker CD44 on human colonic cell lines varies with the degree of cellular differentiation. Carcinoembryonic antigen and/or CA19-9 were expressed in all four human colon adenocarcinoma cell lines, but not in the normal colon fibroblast cells (CCD-18Co). Using these two MoAbs appeared to be a more reliable measure of the state of differentiation of human colon adenocarcinoma cells.