long blocks of adjacent IdoA residues. Using mass spectrometry analysis of isolated CS/DS, we reveal that the relative content of IdoA is decreased in blocks and in alternating structures. Intriguingly, there is thus an apparent discrepancy between higher epimerase activity in tumor tissue and lower relative content of alternating and blocks of IdoA structures. This discrepancy could simply be explained by the presence of isolated IdoA structures that were not included in the mass spectrometry analyses. Alternatively, induction of the turnover of IdoA-containing DS oligosaccharides in tumors may cause the release of sequestered HGF and additional growth factors from CS/DS PGs in the stroma resulting in increased accessibility to and stimulation of tumor cells.
