CIC bioGUNE
Published February 6, 2019 | Version v1
Journal article Open

Structure-Based Design of Potent Tumor-Associated Antigens: Modulation of Peptide Presentation by Single-Atom O/S or O/Se Substitutions at the Glycosidic Linkage

Authors/Creators

  • 1. Departamento de Química, Universidad de La Rioja
  • 2. Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa
  • 3. Center for Biomolecular Nanotechnologies@UniLe, Istituto Italiano di Tecnologia (IIT)
  • 4. Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, BIFI-IQFR (CSIC)
  • 5. Departament de Química Analítica i Química Organica, Facultat de Química, Universitat Rovira i Virgili
  • 6. CIC bioGUNE. Ikerbasque, Basque Foundation for Science. Department of Organic Chemistry II, Faculty of Science & Technology, University of the Basque Country
  • 7. Instituto de Química Orgánica General, IQOG-CSIC
  • 8. CIC bioGUNE. Departamento de Química, Universidad de La Rioja
  • 9. Department of Chemistry, University of Cambridge. Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa

Description

GalNAc-glycopeptides derived from mucin MUC1 are an important class of tumor-associated antigens. α-O-glycosylation forces the peptide to adopt an extended conformation in solution, which is far from the structure observed in complexes with a model anti-MUC1 antibody. Herein, we propose a new strategy for designing potent antigen mimics based on modulating peptide/carbohydrate interactions by means of O → S/Se replacement at the glycosidic linkage. These minimal chemical modifications bring about two key structural changes to the glycopeptide. They increase the carbohydrate–peptide distance and change the orientation and dynamics of the glycosidic linkage. As a result, the peptide acquires a preorganized and optimal structure suited for antibody binding. Accordingly, these new glycopeptides display improved binding toward a representative anti-MUC1 antibody relative to the native antigens. To prove the potential of these glycopeptides as tumor-associated MUC1 antigen mimics, the derivative bearing the S-glycosidic linkage was conjugated to gold nanoparticles and tested as an immunogenic formulation in mice without any adjuvant, which resulted in a significant humoral immune response. Importantly, the mice antisera recognize cancer cells in biopsies of breast cancer patients with high selectivity. This finding demonstrates that the antibodies elicited against the mimetic antigen indeed recognize the naturally occurring antigen in its physiological context. Clinically, the exploitation of tumor-associated antigen mimics may contribute to the development of cancer vaccines and to the improvement of cancer diagnosis based on anti-MUC1 antibodies. The methodology presented here is of general interest for applications because it may be extended to modulate the affinity of biologically relevant glycopeptides toward their receptors.

Notes

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/articlesonrequest/AOR-xmtdrFJNKx2Ecn8UZywr. We thank the Ministerio de Economıa y Competitividad (projects CTQ2015-67727-R, CTQ2013-44367-C2-2-P, CTQ2015-64597-C2-1P, CTQ2017-89750-R, CTQ2017-90088-R, CTQ2015-70524-R, and BFU2016-75633-P) and the Italian Ministry of Education, University and Research (MIUR) (PRIN 2015 contract no. 2015RNWJAM). I.C. thanks Universidad de La Rioja for an FPI grant. A.G. and G.J.L.B. thank FCT Portugal (Ph.D. studentship, SFRH/BD/115932/2016 and FCT Investigator IF/00624/2015, respectively). G.J.L.B. holds a Royal Society URF (UF110046 and URF\R\180019) and an ERC StG (TagIt, GA no. 676832). F.C. and G.J.L.B. thank the EU (Marie-Sklodowska Curie ITN, Protein Conjugates, GA no. 675007). O.B. and G.J.-O. are Ramon y Cajal Fellows (RYC-2015-17705 and RYC-2013-14706, respectively). R.H-G. thanks Agencia Aragonesa para la Investigacion y Desarrollo (ARAID) and the Diputación General de Aragon (DGA, E34_R17) for ́ financial support. The research that led to these results also attracted funding from the FP7 (2007-2013) under BioStruct-X (grant agreement no. 283570 and BIOSTRUCTX_5186). We also thank the ALBA synchrotron radiation source, in particular, the beamline XALOC facility. We thank Emanuele Papini and Regina Tavano (University of Padua, Italy) for insightful discussions about the immunogenicity of glycopeptidefunctionalized AuNPs and Vito Maggi and Valentina Rosato (IIT-Lecce) for expert technical assistance. Computational resources of CESGA (Santiago de Compostela) and BERONIA (Universidad de La Rioja) were used in this work. The authors thank Vikki Cantrill for her help with the preparation and editing of this article.

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Additional details

Funding

European Commission
TagIt - A Minimal-Tag Bioorthogonal Labelling Approach to Protein Uptake, Traffic and Delivery 676832
European Commission
ProteinConjugates - A training network for the chemical site-selective modification of proteins: Preparation of the next-generation of therapeutic chemically-defined protein conjugates 675007