Purified plasma membranes were prepared from L1210
ascites tumor cells and analyzed for their
protein and
carbohydrate composition. Conditions were developed for treating the isolated plasma membranes with Vibrio cholerae
neuraminidase (VCN) so that 88% of the
N-acetylneuraminic acid was removed without changing
membrane proteins or other membrane
carbohydrate constituents. The VCN-induced modifications were characterized by labeling VCN-treated and untreated L1210 cells by the
galactose oxidase:
sodium [3H]
borohydride procedure. This showed that
N-acetylneuraminic acid is the predominant saccharide at the nonreducing terminus of plasma membrane
glycoproteins and that
galactose and/or N-
acetylgalactosamine residues are penultimate to these. VCN modification exposed the penultimate residues and was not limited to any single plasma membrane
glycoprotein. DBA/2J mice were given i.p.
injections of VCN-treated or untreated membranes and were challenged 3 weeks later with 10(4) viable L1210 cells. Mice pretreated with VCN-treated membranes resisted the
tumor challenge; those receiving untreated membranes or no treatment succumbed to the
tumor. Our results demonstrate that appropriately modified plasma membranes can be used to induce resistance to
tumor growth. They also suggest that
tumor cell membrane
carbohydrate structures have an important role in this phenomenon.