Bottom-Up Glycomics

We have developed an approach to the analysis of glycans in whole biospecimens in which the complex sugar polymers are broken down in a way that conserves both monosaccharide and linkage information.  In short, the technique consists of applying glycan methylation analysis (a.k.a. “linkage analysis”) to whole biofluids and homogenized tissues in a quantitatively reproducible manner.  N-, O-, and lipid-linked glycans are all captured by the technique.

The approach is complimentary to traditional glycan analysis techniques that profile and quantify the relative abundance of different intact glycans.  Using our bottom-up approach we are able to condense unique glycan features such as “core fucosylation”, “6-sialylation”, “beta-1,6-branching”, and “bisecting GlcNAc” into single analytical signals.  We continue to develop the technology as a general technique for the analysis of glycans in complex samples and we are working to apply this technology toward the development of novel glycan-based markers of cancer and other glycan-affective diseases.

Our latest findings were recently published in the following article:

Ferdosi, S., Rehder, D.S., Maranian, P., Castle, E.P., Ho, T.H., Pass, H.I., Cramer, D.W., Anderson, K.S., Fu, L., Cole, D.E.C., Le, T., Wu, X., Borges, C.R. Stage Dependence, Cell-Origin Independence, and Prognostic Capacity of Serum Glycan Fucosylation, β1-4 Branching, β1-6 Branching, and α2-6 Sialylation in Cancer. J Proteome Res, epub Nov 12, 2017. doi: 10.1021/acs.jproteome.7b00672

Figure 1: Conceptual overview of our approach to the analysis of glycans as cancer markers. As illustrated, an upregulated GT (e.g., GnT-V) causes an increase in the quantity of specific uniquely linked glycan monosaccharide residues (glycan “nodes”)—which can lead to formation of a mixture of heterogeneous whole-glycan structures at low copy number each—all of which, together, can be difficult to detect and quantify consistently.  But when the glycan “nodes” are pooled together analytically from amongst all the aberrant glycan structures their combined numbers add up to produce larger-than-normal GC-MS signals (actual extracted ion chromatograms from 10-µl blood plasma samples shown).  [Numbers adjacent to monosaccharide residues in glycan structures indicate the position at which the higher residue is linked to the lower residue.  If no linkage positions are indicated in the chromatogram annotation the residue is either in the terminal position or free in solution (e.g. glucose).  All residues link downward via their 1-position. Split in chromatogram indicates change in extracted ion chromatograms.]