A Tandem Enzymatic Approach for Detecting and Imaging Tumor-Associated Thomsen–Friedenreich Antigen Disaccharide

The
disaccharide galactose-β1,3-N-acetylgalactosamine
(Galβ1,3-GalNAc) attached to serine and/or threonine residues
of proteins, also known as the Thomsen–Friedenreich (TF) antigen,
is highly expressed in various types of human carcinomas. It has been
shown to contribute to tumor development, progression, and metastasis.
However, current methods have limited power in detecting and imaging
TF antigens among a variety of complex cell-surface glycans. Here
we describe a tandem enzymatic strategy to detect and label TF antigen
disaccharide with high sensitivity and selectivity. We demonstrate
that this strategy enables detection of TF antigens on proteins, profiling
and identification of unknown TF antigen-modified glycoproteins, and
simultaneous labeling of multiple forms of complex glycan motifs on
the same cell. This approach expands the capability of glycan labeling
to probe the functional role of TF antigens in cancer biology.