Convergent Solid-Phase Synthesis of Macromolecular MUC1 Models Truly Mimicking Serum Glycoprotein Biomarkers of Interstitial Lung Diseases

Synthetic macromolecular MUC1 glycopeptides have been used to unravel molecular mechanisms in antibody recognition of disease-specific epitopes. We have established a novel synthetic strategy for MUC1 tandem repeats having complex O-glycosylation states at each repeating unit based on convergent solid-phase fragment condensation under microwave irradiation. We have accomplished the synthesis of 77 amino acid MUC1 glycopeptides (MW = 12 759) having three major antigenic O-glycoforms [Tn, core 1 (T), and core 2 structures] at 10 designated positions out of 19 potential O-glycosylation sites. We demonstrate that the macromolecular MUC1 glycopeptide displaying the essential glycopeptidic neoepitope Pro-Asp-Thr­(sialyl-T)-Arg-Pro-Ala-Pro at two different tandem repeats is an excellent serum MUC1 model showing ideal stoichiometric binding with anti-KL6/MUC1 antibody in the sandwich ELISA to quantify human serum KL6/MUC1 levels as a critical biomarker of interstitial lung diseases.