Glycans attached to proteins have essential roles in many biological processes. Certain carbohydrates attached to proteins are characteristically expressed on cancer cells, and detected by immune system as a disease indicator.
It is reasonable to ask if epitopes on malignant cells are due to the presence of novel carbohydrates, exposition of previously hidden amino acid sequences or both hypotheses.
To address this question, we selected mucin 1 (MUC1) as an object of study. MUC1 is a heavily O-glycosylated protein that manifests a different glycan profile in tumoral cells. MUC1 expressing N-acetyl galactosamine (GalNAc) has been found in several types of carcinomas. First, we obtained a mono-glycan MUC1 library including GalNAc in all potential Ser/Thr positions. All synthetic glycopeptides were synthesized by microwave-assisted solid-phase approach and “double activation-like” method.1
Next, we selected two different groups of monoclonal antibodies (mAb) to be evaluated by microarray assay and STD-NMR. Microarray technique is a powerful platform that allows to discriminate between low to high affinity epitope. Further, STD-NMR provides information of the ligand-receptor interaction at the molecular level.
As result, we found that each group of mAb has a different binding mode by recognition of different regions and moieties. We could confirm that mAbs are able to recognize glycans attached to peptides in a sequence-dependent manner.
In conclusion, the combined strategy of microarray and STD-NMR can be employed to unveil the key minimal structural features that modulate antigen-antibody recognition with application on diagnosis and the development of novel anticancer vaccines.2