Synthesis of tumor associated sialyl-T-glycopeptides and their immunogenicity.
Sialyl-T-glycopeptides were synthesized by solid-phase techniques, using a PEGA resin as the solid support. An appropriately protected building block containing alpha-Neu5Ac-(2 --> 3)-beta-Gal-(1 --> 3)-alpha-GalN3-(1-->) attached to Fmoc-Thr/Ser-OPfp was employed in a solid phase glycopeptide assembly of a 10-mer glycopeptide, using a general Fmoc/OPfp-ester strategy. Reduction of the azido group of the GalN3 residue was effected on solid-phase, using DTT and DBU. After acidolytic cleavage from the resin, the methyl ester of the sialic acid residue and acetyl groups were removed with 30% NaOMe/MeOH in MeOH and water pH 14, at -30 degrees C for 2 h. At this low temperature, the highly basic conditions did not result in any detectable beta-elimination. However, one O-acetyl group, located at the 2-position of the Gal was resistant to hydrolysis. To remove this remaining acetyl group, reaction with hydrazine hydrate in CHCl3 and MeOH at room temperature for 2.5 h was successful. The two target sequences of sialyl-T-glycopeptides were obtained in good yield. In contrast to the the analogs carrying the T-antigen, the Sial-T-glycopeptides were nonimmunogenic, supporting the idea that the sialylation is a method of circumventing the recognition by the immune system.
Komba
S
S
Carlsberg Laboratory, Department of Chemistry, Valby, Copenhagen, Denmark.
Werdelin
O
O
Jensen
T
T
Meldal
M
M
D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry* / Q000494:pharmacology; D002240:Carbohydrate Sequence; D005260:Female; D006020:Glycopeptides / Q000138:chemical synthesis* / Q000494:pharmacology; D007114:Immunization; D008198:Lymph Nodes / Q000473:pathology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000628:therapy; D013601:T-Lymphocytes / Q000276:immunology
D015295:Antigens, Tumor-Associated, Carbohydrate; D006020:Glycopeptides; C055491:sialosyl-Tn antigen