RESUMO
This study presents the synthesis of the novel protected O-glycosylated amino acid derivatives 1 and 2, containing ßGalNAc-SerOBn and ßGalNAc-ThrOBn units, respectively, as mimetics of the natural Tn antigen (αGalNAc-Ser/Thr), along with the solid-phase assembly of the glycopeptides NHAcSer-Ala-Pro-Asp-Thr[αGalNAc]-Arg-Pro-Ala-Pro-Gly-BSA (3-BSA) and NHAcSer-Ala-Pro-Asp-Thr[ßGalNAc]-Arg-Pro-Ala-Pro-Gly-BSA (4-BSA), bearing αGalNAc-Thr or ßGalNAc-Thr units, respectively, as mimetics of MUC1 tumor mucin glycoproteins. According to ELISA tests, immunizations of mice with ßGalNAc-glycopeptide 4-BSA induced higher sera titers (1:320 000) than immunizations with αGalNAc-glycopeptide 3-BSA (1:40 000). Likewise, flow cytometry assays showed higher capacity of the obtained anti-glycopeptide 4-BSA antibodies to recognize MCF-7 tumor cells. Cross-recognition between immunopurified anti-ßGalNAc antibodies and αGalNAc-glycopeptide and vice versa was also verified. Lastly, molecular dynamics simulations and surface plasmon resonance (SPR) showed that ßGalNAc-glycopeptide 4 can interact with a model antitumor monoclonal antibody (SM3). Taken together, these data highlight the improved immunogenicity of the unnatural glycopeptide 4-BSA, bearing ßGalNAc-Thr as Tn antigen isomer.
