Research Of Serum N-Glycan Isomers In Colorectal Cancer Using LC-MS

[Objective]To study the relative abundance variation of the N-glycan isomers in the serum of patients with colorectal cancer and to find the isomer-specific N-glycan biomarkers for the diagnosis of colorectal cancer. [Methods]A process of methylamine reduction for the serum samples from 60 cases of patients with colorectal cancer and 34 cases of healthy population in Tongji hospital from January 2010 to December 2013. All the patients were diagnosed by histological examination and were not treated with surgery, chemotherapy or any other interventions. The Nano LC-ESI-MS was applied to detect the relative abundance of N-glycan isomers in the serum. The data was statistically analyzed to identify specific N-glycan isomers which were significantly different among the patients and the controls. ANOVA was used for the comparison among multiple groups and the independent sample T-test was used for the comparison between two groups. ROC curves were plotted and the area under the curve(AUC) was applied to estimate the value for the diagnosis of colorectal cancer. [Results]There were 5 N-glycan isomers which showed significant differences between the cancer patients and the healthy controls, which were H4N3F1, H5N3F1, H5N4S1F1, H5N4S2F1 and H5N5F1. Among these, H4N3F1-P6?H5N3F1-P3?H5N4S1F1-P8?H5N4S2F1-P4 and H5N5F1-P4 were the most significantly different isomers, which showed moderate level of diagnosis value with the AUC ranging from 0.70~0.85. When three of the five isomers(H5N3F1-P3, H5N4S1F1-P8 and H5N5F1-P4) were combined, the AUC were elevated to 0.913. In addition, the five isomers also displayed significant differences when the CRC patients in early stage were compared to the healthy controls. Especially, when three isomers from the same N-glycan(H5N5F1-P1, P4 and P8) were incorporated into the same ROC curve, the AUC was increased to 0.896, showing satisfactory performance to discriminate the early stage patients from healthy controls. [Conclusion]N- glycan isomers could serve as potential tumor biomarkers for the diagnosis of CRC.