ST6GALNAC3 is a sialyltransferase that catalyzes the transfer of sialyl groups to GalNAc residues on glycoproteins and glycolipids, forming alpha-2,6-linkages 12. The enzyme preferentially acts on glycolipids and catalyzes ganglioside GD1α biosynthesis from GM1b 12. GD1α functions as a critical adhesion molecule in neuronal cell interactions and metastatic processes 2. ST6GALNAC3 operates alongside ST6GALNAC4 in synthesizing disialyl-T structures essential for maintaining high endothelial venule integrity in lymph nodes; their combined deficiency causes spontaneous hemorrhage 3. In disease contexts, ST6GALNAC3 shows significant clinical relevance: its promoter hypermethylation serves as a cancer-specific biomarker in prostate cancer with high diagnostic accuracy (AUC 0.917-0.995) and is detectable in circulating tumor DNA from patient serum 4. In gastric cancer, ST6GALNAC3 promotes arachidonic acid metabolism and prostaglandin synthesis, increasing M2 macrophage infiltration and inducing epithelial mesenchymal transformation as a prognostic marker 5. In ovarian cancer, the adipose microenvironment upregulates ST6GALNAC3 expression, promoting tumor cell hypersialylation that enables immune evasion and metastatic colonization 6. Additionally, ST6GALNAC3 associates with EEG theta power variability and alcoholism susceptibility 7, suggesting roles in neurobiological processes.