The new face of nucleolin in human melanoma.

Nucleolin is multifunctional protein mainly present in nucleoli but also detected in cytoplasm and plasma membranes. Extranuclear nucleolin differs from the nuclear form by its glycosylation. Studies on expression of nucleolin in breast cancer suggest a possible association to the metastatic cascade. In the present study, Vicia villosa lectin (VVL) precipitation followed by subsequent polyacrylamide gel electrophoresis and mass spectrometry analysis demonstrates nucleolin as a VVL-positive glycoprotein expressed in melanoma. The presence of VVL-positive nucleolin in the melanoma cell membrane and cytoplasm was confirmed by confocal microscopy. Using bioinformatic peptide prediction programs, nucleolin was shown to contain multiple possible MHC class-I binding peptides in its sequence which makes nucleolin an interesting melanoma marker and target for immunodiagnostic and possibly therapeutic purposes.

Characterisation of alpha3beta1 and alpha(v)beta3 integrin N-oligosaccharides in metastatic melanoma WM9 and WM239 cell lines.

It is well documented that glycan synthesis is altered in some pathological processes, including cancer. The most frequently observed alterations during tumourigenesis are extensive expression of beta1,6-branched complex type N-glycans, the presence of poly-N-acetyllactosamine structures, and high sialylation of cell surface glycoproteins. This study investigated two integrins, alpha3beta1 and alpha(v)beta3, whose expression is closely related to cancer progression. Their oligosaccharide structures in two metastatic melanoma cell lines (WM9, WM239) were analysed with the use of matrix-assisted laser desorption ionisation mass spectrometry. Both examined integrins possessed heavily sialylated and fucosylated glycans, with beta1,6-branches and short polylactosamine chains. In WM9 cells, alpha3beta1 integrin was more variously glycosylated than alpha(v)beta3; in WM239 cells the situation was the reverse. Functional studies (wound healing and ELISA integrin binding assays) revealed that the N-oligosaccharide component of the tested integrins influenced melanoma cell migration on vitronectin and alpha3beta1 integrin binding to laminin-5. Additionally, more variously glycosylated integrins exerted a stronger influence on these parameters. To the best of our knowledge, this is the first report concerning structural characterisation of alpha(v)beta3 integrin glycans in melanoma or in any cancer cells.