Flow cytofluorometric analysis of choriogonadotropin-like material on the surface of human and mouse malignant cells.

Quantitation by flow cytofluorometry of the distribution of human choriogonadotropin (hCG)-like material on the surface of various human and mouse tumor cells grown in tissue culture and as solid tumors has been done using fluorescein-tagged rabbit antisera (IgG fraction) to intact hCG and, in one experiment, by use of two monoclonal antibodies specific for hCG. Fibroblasts were used as a negative (nontumorigenic) cell control, and a rabbit antiserum to human hemoglobin was used as reagent control. All malignant cells tested stained more intensely with the anti-hCG serum than with the antihuman hemoglobin serum. Positive reaction with the monoclonal antibodies specific for hCG provided strong evidence that the material stained was identical to hCG. Heterogeneity of the expression of the hCG-like material was notable both within each cell line and between different cell lines. This heterogeneity was not associated with cell-cycle phase. 3T3 fibroblast-like cells in vitro were originally negative for hCG but acquired reactivity with anti-hCG serum after ten passages.