Metastasis accounts for the majority of mortality associated with melanoma, as limited treatment options exist for advanced stages of the disease. Alterations in cell surface glycosylation, in particular, increases in highly branched tetra-antennary N-glycan structures contribute to the invasive and metastatic potential of melanoma cells.  Despite a growing understanding of the role of tetra-antennary N-linked oligosaccharides in melanoma biology, there has been little progress in using these glycans as a screening tool for the early diagnosis of metastasis and predictor of patient prognosis.

Here, we demonstrate a targeted method combining PGC-LC-MS with exoglycosidase digestion for the complete structural characterisation and relative quantitation of N-glycans released from metastatic melanoma lymph node tumours. Released glycans were treated with a full array of exoglycosidase enzymes to assign monosaccharide linkage and confirm terminal epitopes on pools of good and poor prognosis patient samples. The global membrane N-glycosylation profile of tumour tissue from individual patient samples have been compared and glycan structures quantitated before and after selected exoglycosidase combinations to confirm differences in structural features including the degree of branching, sialylation and fucosylation. Over 80 glycan structures were identified, including high mannose, pauci mannose, hybrid and complex type glycans.

This study contributes to our understanding of glycosylation alterations in melanoma metastasis towards using specific glycosylation changes as prognostic markers and specific targets for therapeutic intervention.