Glycoproteomics analysis of colorectal cancer reveals differential alterations of glycoproteins and glycans.

Colorectal cancer (CRC) remains a global health concern, with an urgent need for better early detection and targeted therapies. Our glycoproteomics analysis comparing CRC to paracancerous (PCA) tissue revealed significant alterations. Global proteomic analysis showed more unique proteins in CRC, with differential expression across CRC stages, especially in protein synthesis, translation, and degradation pathways. Despite overall proteomic differences, intact glycopeptide analysis showed high glycosylation similarity between CRC and PCA, with 722 shared glycosites, 2102 shared glycopeptides, and 435 shared glycoproteins. However, a significant shift in CRC's N-glycan composition was observed: an upregulation of high-mannose N-glycans and a decrease in complex N-glycans, including sialoglycans and fucosylated sialoglycans. While glycosylation motif analysis showed conserved peptide sequences, the attached N-glycan types differed remarkably. KEGG pathway analysis suggested that extracellular matrix and lysosomal glycoproteins like COL1A1 and LAMP1 might modulate the PI3K/Akt signaling pathway via TGFβ1-mediated mechanisms, potentially contributing to tumor progression. These findings suggest that while global protein expression changes significantly in CRC, subtle but crucial changes in N-glycan composition, specifically the increase of high-mannose N-glycans and the decrease of complex N-glycans, may play a significant role in tumor progression and metastasis, potentially through modulation of key signaling pathways.