Selectin ligands on human melanoma cells

Area of Science:

• Cell Biology
• Glycobiology
• Cancer Research

Background:

• Melanoma cells express carbohydrate antigens like sialyl LewisX (SLeX) and sialyl Lewisa (SLea).
• These antigens are implicated in cell adhesion mediated by E-selectin, a key molecule in inflammatory responses.

Purpose of the Study:

• To investigate the role of specific Lewis antigens in E-selectin-dependent adhesion of human melanoma cells.
• To determine if endogenous or introduced SLeX/SLea antigens mediate adhesion to endothelial cells.

Main Methods:

• Screening of twelve human melanoma cell lines for expression of Lewis antigens (Lea, SLea, diSLea, SLex, diSLeX).
• Transduction of melanoma cells with Lewis fucosyltransferase (FucT-III) to induce SLeX expression.
• Assessing E-selectin-dependent adhesion to activated human umbilical vein endothelial cells (HUVECs).
• Inhibition studies using glycosylation inhibitors to analyze the role of protein glycosylation.

Main Results:

• Most melanoma lines expressed dimeric sialyl LewisX (diSLeX) and sialyl Lewisa (SLea), but not sialyl LewisX (SLex).
• No endogenous antigens mediated E-selectin-dependent adhesion to HUVECs.
• Transduced cells expressing SLeX exhibited E-selectin-dependent adhesion.
• Glycosylation inhibitors affected adhesion without altering cell surface antigen levels, suggesting protein association is crucial.

Conclusions:

• Endogenous SLeX/SLea-type glycans on melanoma cells are often not protein-associated and do not mediate E-selectin-dependent adhesion.
• E-selectin-dependent adhesion of melanoma cells requires SLeX-type moieties to be presented on specific glycoproteins.