N-glycoproteins bearing β1-6 branched oligosaccharides from the A375 human melanoma cell line analysed by tandem mass spectrometry

Tumour-associated alterations of cell surface glycosylation play a crucial role in the adhesion and metastasis of cancer cells. It is well known that the metastatic potential is associated with increased GIcNAc beta1-6 branching in N-glycans of tumour cells specifically recognized by a lectin from Phaseolus vulgaris leukoagglutinin (PHA-L). We identified proteins bearing GIcNAc beta1-6 branched N-glycans in the A375 human melanoma cell line by affinity chromatography separation on a PHA-L agarose column, followed by immunoidentification and tandem mass spectrometry (MS/MS) analysis. Amongst the proteins identified were integrin subunits alpha(2), alpha(3), alpha(5) and beta(1), as well as N-cadherin and lysosome-associated membrane proteins (LAMP-1 and LAMP-2). In addition, L1, Mac-2 binding protein (Mac-2-BP), activated leukocyte cell adhesion molecule/CD166 (ALCAM) and melanotransferrin were shown to react with PHA-L. Some of these proteins are connected mainly with nervous tissues or the immune system and play a crucial role in cell adhesion processes. The presence of GIcNAc beta1-6 branched oligosaccharides in these proteins may influence their adhesion properties, reducing adhesion of the cells to the extracellular matrix (ECM) and thus facilitating tumour cell invasion. (C) 2004 Lippincott Williams Wilkins.