Glycoprotein metabolism in skin cancer: synthesis, pool size, and partial characterization of glycoproteins in the rat basosquamous cell carcinoma.

Uptake of fucose, glucosamine, galactose, and mannose and the incorporation of these sugars into glycoconjugates have been quantified in a model epithelial tumor, the basosquamous cell carcinoma of the rat. Following isolation of glycoprotein and papain digestion, the fucosylated glycopeptides were fractionated according to molecular weight (Mr) and by affinity chromatography. Analysis of cellular material revealed a 2- to 3-fold reduction in the proportion of high-Mr fucopeptides synthesized by the tumor compared with normal epidermis, accompanied by a profound block in the incorporation of galactose into glycoconjugates. Parallel investigation of carbohydrate removed from the cell surface with trypsin or spontaneously shed into the medium indicated a striking decrease in the total release of fucopeptides from the tumor; the Mr was (respectively) normal or increased. Thus the fucopeptide abnormality appears to be accounted for almost entirely by a shift toward accumulation of low-Mr material at internal locations within the cell.