Next, CS/DS was digested by chondroitinase B alone, resulting in disaccharides from DS regions containing at least two adjacent IdoA residues. The absolute content of IdoA disaccharides was unaffected in cancer biopsies compared to normal tissues (amount of IdoA/weight of tissue; Fig 5D). However, there was a 5-fold increase of CS/DS content in tumor tissues (Fig 5A). Collectively, these data show that the relative amount of IdoA/chain (% of IdoA / IdoA + GlcA) decreased in tumor compared to control tissues. In summary, total CS/DS levels were increased in ESCC samples. The average structure of the chains derived from tumor tissues was altered; 6-monosulfated disaccharides were increased, and 4-O-monosulfated as well as disulfated disaccharides and IdoA-containing structures were decreased.
