title: Identification of a novel cancer-specific immunodominant glycopeptide epitope in the MUC1 tandem repeat.
abstract: The cell membrane mucin MUC1 is over-expressed and aberrantly glycosylated in many cancers, and cancer-associated MUC1 glycoforms represent potential targets for immunodiagnostic and therapeutic measures. We have recently shown that MUC1 with GalNAcalpha1-O-Ser/Thr (Tn) and NeuAcalpha2-6GalNAcalpha1-O-Ser/Thr (STn) O-glycosylation is a cancer-specific glycoform, and that Tn/STn-MUC1 glycopeptide-based vaccines can override tolerance in human MUC1 transgenic mice and induce humoral immunity with high specificity for MUC1 cancer-specific glycoforms (Sorensen AL, Reis CA, Tarp MA, Mandel U, Ramachandran K, Sankaranarayanan V, Schwientek T, Graham R, Taylor-Papadimitriou J, Hollingsworth MA, et al. 2006. Chemoenzymatically synthesized multimeric Tn/STn MUC1 glycopeptides elicit cancer-specific anti-MUC1 antibody responses and override tolerance. Glycobiology. 16:96-107). In order to further characterize the immune response to Tn/STn-MUC1 glycoforms, we generated monoclonal antibodies with specificity similar to the polyclonal antibody response found in transgenic mice. In the present study, we define the immunodominant epitope on Tn/STn-MUC1 glycopeptides to the region including the amino acids GSTA of the MUC1 20-amino acid tandem repeat (HGVTSAPDTRPAPGSTAPPA). Most other MUC1 antibodies are directed to the PDTR region, although patients with antibodies to the GSTA region have been identified. A panel of other MUC1 glycoform-specific monoclonal antibodies was included for comparison. The study demonstrates that the GSTA region of the MUC1 tandem repeat contains a highly immunodominant epitope when presented with immature short O-glycans. The cancer-specific expression of this glycopeptide epitope makes it a prime candidate for immunodiagnostic and therapeutic measures.
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen N, Denmark.
authors.forename: Mads A
authors.initials: MA
authors.lastname: Tarp
authors.forename: Anne Louise
authors.initials: AL
authors.lastname: Sørensen
authors.forename: Ulla
authors.initials: U
authors.lastname: Mandel
authors.forename: Hans
authors.initials: H
authors.lastname: Paulsen
authors.forename: Joy
authors.initials: J
authors.lastname: Burchell
authors.forename: Joyce
authors.initials: J
authors.lastname: Taylor-Papadimitriou
authors.forename: Henrik
authors.initials: H
authors.lastname: Clausen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D018604:Epitope Mapping; D005260:Female; D006020:Glycopeptides / Q000737:chemistry / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D016056:Immunodominant Epitopes / Q000737:chemistry* / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D018396:Mucin-1 / Q000737:chemistry / Q000276:immunology*; D009369:Neoplasms / Q000276:immunology*; D020449:Repetitive Sequences, Amino Acid
chemical_list: D000911:Antibodies, Monoclonal; D006020:Glycopeptides; D007106:Immune Sera; D016056:Immunodominant Epitopes; D018396:Mucin-1