Isolation and identification of mannose‐binding proteins and estimation of their abundance in sera from hepatocellular carcinoma patients

The interaction of glycan‐binding proteins ( GBP s) and glycans plays a significant biological role that ranges from cell–cell recognition to cell trafficking, and glycoprotein targeting. The anomalies of GBP s related to the types and/or quantities were not clearly known in cancer incidence. It is imperative to identify and annotate the GBP s related with the canceration. Here the mannose‐binding proteins ( MBP s) from the clinical sera were isolated and identified by the mannose‐magnetic particle conjugates and the high‐accuracy MS analysis. Seventy‐five MBP s from normal donors’ sera and 79 MBP s from hepatocellular carcinoma patients’ sera were identified and annotated. By using the stringent criteria of exponentially modified protein abundance index (em PAI ) quantification, 12 MBP s were estimated to be significantly upregulated (emPAI ratio > 4) and nine MBP s were estimated to be significantly downregulated (emPAI ratio < 0.25) in the hepatocellular carcinoma sera. Real‐time quantitative PCR , W estern blotting, and protein microarrays were also used to confirm the altered MBP s expression level and the specific binding between the isolated MBP s and mannose. The sequence recognition motifs and structure preference of the isolated MBP s were characterized. The functional enrichment analysis revealed that over 57% of the isolated MBP s were binding protein and the upregulated MBP s were involved in cell death, tumor progression, and macromolecular complex remodeling.