Flow Cytometric Analysis of Heterogeneity in Blood Group-related Antigen Expression in a Human Urinary Bladder Carcinoma Cell Line, 647V

Previous immunohistological studies showed a relationship between expression of blood group-related antigens (BG-Ag) and invasive potential in human urinary bladder carcinoma, but the marked variability of antigen staining within many individual tumors has obscured the biological basis of this finding. We studied the expression of the A, H, and T (Thomsen-Friedenreich) BG-Ag by flow cytometry in a human bladder carcinoma cell line (647V) using fluoresceinated BG-Ag-specific lectins (Dolichos bifloris, Ulex europaeus, and Arachis hypogaea). Cell cycle compartments were quantitated by flow cytometry using propidium iodide staining. Expression of all three antigens was highly variable, but staining for each antigen produced a distinct profile. T antigen expression appeared independent of A or H antigen expression. Cell populations sorted by T antigen expression showed heritable antigenic differences persistent over many weeks in culture. However, much of the T antigen variability was nonheritable, since the stable staining profiles of the sorted cells were intermediate between the parental and the profiles obtained immediately after sorting. The nonheritable antigenic variation did not appear entirely explainable by cell size or cell cycle fluctuation. These results were confirmed by isolating 64 clones from the dim part of the T antigen staining profile, 19 of which had a persistently dim phenotype. The variability of BG-Ag expression by human bladder carcinoma cells in vitro may explain the staining patterns observed in the study of antigen expression in resected human bladder carcinomas.