Comparison of cell-surface glycoproteins of rat hepatomas and embryonic rat liver.

Cell-surface glycoprotein of 3 rat hepatoma strains and late-embryonic liver was metabolically labelled in vivo with [3H]- or [14C]-fucose. Trypsinization of the cells and exhaustive pronase digestion of combined hepatoma-liver trypsinates followed by gel filtration over Sephadex-Biogel mixtures, yielded elution profiles that contained more early-eluting (high-mol.-wt.) glycopeptides for hepatomas than for liver. At least 3 factors were identified which acted to augment the fraction of early-eluting tumour glycopeptides: (a) increase of neuraminidase-sensitive sialic acid, (b) increase of neuraminidase-insensitive sialic acid that was sensitive to mild HCl hydrolysis, and (c) presence of sugar sulphate groups contributing to a restricted extent, relative to possible unknown factor(s). Whether (a), (b) or (c) operated depended on the hepatoma strain or its mode of growth. Notwithstanding these differences in the nature of the increase in early-eluting glycopeptides, the increase itself appears not to be due to growth per se, nor to an embryonic expression, but rather may serve as a marker of tumourigenicity.