Control of metastasis by Asn-linked, β1–6 branched oligosaccharides in mouse mammary cancer cells

Studies in cell lines and malignant human tissues have shownthat increased cell-surface Asn-linked β1–6(GlcNAcβ1–6Man)branching is associated with increased tumorigenic and meta-static properties. In this study, three mouse mammary cancercell lines were transfected with an expression vector contain-ing the mouse cDNA for N-acetylglucosaminyltransferase V(GlcNAcT-V EC 2.4.1.155), the glycosyltransferase respon-sible for initiating β1–6 branching on Asn-linked carbo-hydrates. The cell lines were screened for increased cytotoxic-ity to L-PHA, a lectin specific for β1–6 branching structures.Cell lines exhibiting increased L-PHA cytotoxicity expressedincreased levels of β1–6 branching structures. Northern blotsdetected the presence of GlcNAcT-V transcribed from theexpression vector in the L-PHA sensitive cell lines. Afterinjection into the tail veins of mice, transfected cell lines withincreased β1–6 branching on the cell surface formed elevatedlevels of lung tumors relative to control transfected cell lines(P < 0.002). Western blots of membrane proteins fromGlcNAcT-V transfected and control cells probed with the lec-tins DSA and WGA did not show an increase in polyN-acetyl-lactosamine and sialic acid content in the transfected celllines. These results demonstrate that a specific increase inβ1–6 branching due to an elevation in GlcNAcT-V expressionincreases metastatic potential.Key words: β1–6 branched oligosaccharides/GlcNAcT-V/transfection/metastasisIntroductionThe trimannosyl core of Asn-linked oligosaccharides may containβ1–6(GlcNAcβ1–6Manα1–6Manβ1-) in tri- and tetra-antennarybranches, which is regulated by the expression of UDP-GlcNAc:α