Asparagine-linked oligosaccharides in murine tumor cells: comparison of a WGA-resistant (WGAr) nonmetastatic mutant and a related WGA-sensitive (WGAs) metastatic line.

Abstract

MDW40, a wheat germ agglutinin-resistant (WGAr) mutant of the highly metastatic tumor cell line called MDAY-D2, is restricted to local growth at the s.c. site of inoculation. The WGAr tumor cells acquire metastatic ability by fusing spontaneously with a normal host cell followed by chromosome segregation, a process accompanied by reversion of the WGAr phenotype (i.e., WGAs). Since lectin-resistant mutant cell lines often have oligosaccharide alterations that may affect membrane function and consequently metastatic capacity, the major Asn-linked glycopeptides in WGAr and WGAs cell lines were compared. [2-3H]mannose-labeled glycopeptides were separated into 4 fractions on a DEAE-cellulose column and then further fractionated on a concanavalin A-Sepharose column. Glycopeptide structures were determined by sequential exoglycosidase digestion followed by chromatography on lectin/agarose and Bio-Gel P-4 columns and proton NMR analysis. The metastatic WGAs cells had a sialylated poly-N-acetyllactosamine-containing glycopeptide which was absent in the nonmetastatic mutant cell line. Unique to the mutant was a neutral triantennary class of glycopeptide lacking sialic acid and galactose; the WGAr lesion therefore appeared to be a premature truncation of the antennae of the poly-N-acetyllactosamine-containing glycopeptide found in the WGAs cells. High mannose glycopeptides containing 5-9 mannose residues constituted a major class in both WGAr and WGAs cells. Lysates of both wild-type and mutant cells had similar levels of galactosyltransferase activity capable of adding galactose to the N-acetylglucosamine-terminated glycopeptide isolated from mutant cells; the basis of the WGAr lesion remains to be determined.