Design of α-S-Neoglycopeptides Derived from MUC1 with a Flexible and Solvent-Exposed Sugar Moiety

Abstract

The use of vaccines based on MUC1 glycopeptides is a promising approach to treat cancer. We present herein several sulfa-Tn antigens incorporated in MUC1 sequences that possess a variable linker between the carbohydrate (GalNAc) and the peptide backbone. The main conformations of these molecules in solution have been evaluated by combining NMR experiments and molecular dynamics simulations. The linker plays a key role in the modulation of the conformation of these compounds at different levels, blocking a direct contact between the sugar moiety and the backbone, promoting a helix-like conformation for the glycosylated residue and favoring the proper presentation of the sugar unit for molecular recognition events. The feasibility of these novel compounds as mimics of MUC1 antigens has been validated by the X-ray diffraction structure of one of these unnatural derivatives complexed to an anti-MUC1 monoclonal antibody. These features, together with potential lack of immune suppression, render these unnatural glycopeptides promising candidates for designing alternative therapeutic vaccines against cancer.

Principles of mucin structure: implications for the rational design of cancer vaccines derived from MUC1-glycopeptides

“…The same group analysed numerous sulfa-Tn antigens that feature a variable linker between the carbohydrate (GalNAc) and the peptide backbone 43 (Fig. 12D).…”

“…Notably, the linker avoids interactions between the peptide and the carbohydrate, which allows the underlying peptide to adopt largely folded conformations. 43 application in the generation of improved antibodies for immunotherapeutic use, diagnostic tools, and design of MUC1-based cancer vaccines. For instance, Nishimura and co-workers performed an exhaustive study to determine the specific epitope structure of anti-KL-6 MAb.…”

Site‐Selective Modification of Proteins with Oxetanes

“…The display of βGalS as a representative example of carbohydrate epitope was further studied by molecular dynamics (MD) simulations and the result compared to a general aliphatic linker with the same number of carbons, obtained by thiol‐ene chemistry at S ‐allyl cysteine (Sac) (Figure d) . Interestingly, the oxetane linker in 7 a proved to be a more rigid scaffold than that in 8 for the presentation of βGalS as determined by the analysis of the angle between Cα‐Cβ‐C 1 where a major population is observed.…”

“…[5] The displayofbGalS as arepresentative example of carbohydrate epitope wasf urther studied by molecular dynamics (MD) simulations and the result compared to ag eneral aliphatic linker with the same number of carbons, obtainedb yt hiol-ene chemistry at S-allyl cysteine( Sac) (Figure 3d). [15] Interestingly, the oxetane linker in 7a provedt ob eam ore rigid scaffold than that in 8 for the presentation of bGalS as determined by the analysiso ft he angle between Ca-Cb-C 1 where am ajor population is observed. Ta ken together,w eb elieve this rigid, non-aromatic, and soluble linker will be advantageous, for example,i nt he development of homogeneous carbohydrate- based vaccine conjugates,h opefully,w ith reduced anti-linker response.…”

Chemoselective Glycosylation of Peptides through S‐Alkylation Reaction

“…Some protocols for the synthesis of SPPS building blocks consist of reacting the nucleophilic thiol‐carbohydrate with a suitable amino acid derivative. In a recently published work aimed at incorporating a carbohydrate moiety in Tn antigen peptides, the S‐alkylation of a thio‐α‐ d ‐galactopyranose (GalNAc‐α‐SH) with a bromoalanine derivative was carried out . The reaction was promoted by activated molecular sieves (MS).…”