title: Tumor cell surface beta 1-4-linked galactose binds to lectin(s) on microvascular endothelial cells and contributes to organ colonization.
abstract: Cell surface carbohydrate structures acting as ligands for tissue specific mammalian lectins have been implicated in cell-cell interactions during embryogenesis, lymphocyte homing, and tumor cell metastasis. In this report, we provide evidence that beta 1-4 linked galactose (Gal) residues in N-linked oligosaccharides on the surface of blood born tumor cells serve as a ligand for binding to microvascular endothelial cells. D36W25, a class 1 glycosylation mutant of the MDAY-D2 lymphoreticular tumor cell line, lacks sialic acid and Gal in cellular glycans due to a defect in the Golgi UDP-Gal transporter. Using UDP-Gal and bovine galactosyltransferase in vitro, beta 1-4 Gal was restored to the surface of the cells and 70% of the galactosylated glycans persisted for 8 h in vitro at 37 degrees C. Compared to mock-treated D36W25 cells, galactosylated D36W25 cells showed an 80% increase in binding to microvascular endothelial cell monolayers in vitro. The enhanced binding of galactosylated D36W25 cells to endothelial cell was inhibited by the addition of lactosamine-conjugated albumin to the assay. Consistent with these observations, swainsonine and castinospermine, two inhibitors of N-linked processing that result in loss of lactosamine antennae inhibited the binding of wild-type MDAY-D2 cells to endothelial cells in vitro. Injection of radiolabeled tumor cells into the circulation of syngeneic mice, showed that galactosylation of D36W25 cells resulted in 2-3 more tumor cells retained in the lungs and livers. In addition, galactosylation of D36W25 cells increased by 30-fold the number of visible liver metastases on inspection 4 wk after tumor cell injection. These results suggest that beta 1-4Gal-binding lectins on microvascular endothelial cells can contribute to retention and secondary tumor formation of blood born tumor cells. With the increasing availability of purified glycosyltransferases, reconstruction of a variety of carbohydrate sequences on the surface of class 1 mutants provides a controlled means of studying carbohydrate-lectin interactions on viable cells.
authors.affiliation: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario.
authors.forename: I
authors.initials: I
authors.lastname: Cornil
authors.forename: R S
authors.initials: RS
authors.lastname: Kerbel
authors.forename: J W
authors.initials: JW
authors.lastname: Dennis
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D005434:Flow Cytometry; D005690:Galactose; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors; D007212:Indolizines; D007700:Kinetics; D037102:Lectins; D008228:Lymphoma, Non-Hodgkin; D051379:Mice; D008811:Mice, Inbred DBA; D009154:Mutation; D009844:Oligosaccharides; D017026:Swainsonine; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000502:physiology*; D054836:Indolizidines
chemical_list: D000470:Alkaloids; D005690:Galactose; D006026:Glycoside Hydrolases; D007212:Indolizines; D037102:Lectins; D009844:Oligosaccharides; D017026:Swainsonine; C037806:castanospermine; D054836:Indolizidines