The Expression of the Epithelial Blood-group Substances: Normal and Malignant Tissues

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Abstract
The blood-group isoantigens are macromolecules localized to the plasma membranes of certain epithelial tissues.2,11-15 These substances are not detectable on the epithelium once it has undergone malignant transformation.2,9,13 Results of this investigation have demonstrated that the loss of detectability of the blood-group isoantigens does not appear to be related to a "masking" effect by an increase in surface sialic acid. Using fluorescein-labeled lectins specific for sugar subunits which are components of the blood-group oligosaccharide chain, it was found that the malignant cells and cells of the para basal layer of normal oral epithelium had high levels of N-acetyl-D-glucosamine (GlcNAC), the subterminal sugar residue of the blood-group chain. The basal cells of normal epithelium and a minority of the malignant cells demonstrated levels of D-galactose-N-acetyl-D-galactosamine, which are the most proximal blood-group sugar subunits, as well as subunits of other membrane antigens. Our results indicate that malignant cells seem to be capable of synthesizing the blood-group oligosaccharide chains to the same level as the normal cells of the para basal layer of stratified squamous epithelium. This level is just subjacent to the terminal D-galactose residue of the blood-group precursor chain. Increased or decreased differentiation characteristics of squamous cell carcinomas did not alter the level of blood-group synthesis. However, there may be a correlation between the level of synthesis of these antigens and the ability of the cells to demonstrate motility and to proliferate.