Poly N-acetyllactosamine substitutions on N- and not O-oligosaccharides or Thomsen-Friedenreich antigen facilitate lung specific metastasis of melanoma cells via galectin-3

Galectin-3 on vascular endothelium has been shown to facilitate lung specific metastasis. Metastatic variants of B16 melanoma were chosen to identify specific ligands that mediate lung colonization via galectin-3. Flow cytometry showed that, galectin-3 binding to cells correlates with surface expression of poly N-acetyllactosamine (polylacNAc) but not with other reported ligands, e.g. Thomsen-Friedenreich (T/Tn) antigen. Immobilized galectin-3 promoted adhesion of melanoma cells in a metastasis dependent manner. Moreover, adhesion and galectin-3 binding to cells were specifically inhibited with lactose. These properties together with lung metastasis were inhibited with N-glycosylation inhibitor Swainsonine (SW), whereas, O-glycosylation inhibitor Benzyl-alpha-N-acetylgalactosamine (BG) had no effect. BG treatment significantly increased expression of T/Tn antigen on low metastatic cells; however, had no effect on their metastatic potential. The studies very comprehensively demonstrate the importance of polylacNAc substitutions on N-oligosaccharides in galectin-3 mediated lung metastasis.