title: Synthesis of MUC1 glycopeptide thioesters and ligation via direct aminolysis.
abstract: MUC1 is a cell-surface, epithelial glycoprotein that forms an essential protective barrier of cells and serves to modulate intercellular communication. During cancer progression, the dysregulation of glycosyltransferases, which serve to elongate cell-surface glycans, leads to aberrant gIycosylation patterns on this glycoprotein. This results in the presentation of well-characterized, tumor-associated carbohydrate antigens (TACAs) which represent important biomarkers for a range of epithelial cancers. The synthesis of well-defined, multivalent MUC1 glycopeptide constructs bearing TACAs therefore represents a viable opportunity for the development of cancer vaccine candidates. We report herein the synthesis of a glycopeptide thioester, comprising the full eicosapeptide variable number tandem repeat (VNTR) region of MUC1, which was prepared bearing multiple copies of the cancer-associated TN antigen. The glycopeptide thioester was prepared on the solid-phase using two different methods on 2-chlorotrityl chloride and sulfamylbutyryl resins. The solid-phase assembly on 2-chlorotrityl chloride resin, followed by thioesterification in solution, afforded the desired thioester in 4% yield over 41 linear steps. Likewise, the glycopeptide thioester was successfully prepared on sulfamylbutyryl resin using an activation and thiol-release strategy in a 9% isolated yield. The resulting peptide thioester was successfully ligated to a deprotected MUC1 glycopeptide using the direct aminolysis ligation to afford a 5.8 kDa, 40 amino acid MUC1 glycopeptide bearing 10 copies of the T(N) antigen. This work represents an important step toward the immunological evaluation of multivalent MUC1 constructs.
authors.affiliation: School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors.forename: Brendan L
authors.initials: BL
authors.lastname: Wilkinson
authors.forename: Candy K Y
authors.initials: CK
authors.lastname: Chun
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Payne
mesh_terms: D006020:Glycopeptides / Q000138:chemical synthesis* / Q000737:chemistry*; D006801:Humans; D018396:Mucin-1 / Q000737:chemistry*
chemical_list: D006020:Glycopeptides; C060192:MUC1 protein, human; D018396:Mucin-1