GCNT1 is a glycosyltransferase that catalyzes the transfer of N-acetylglucosamine (GlcNAc) in beta1-6 linkage to mucin-type core 1 O-glycans, forming branched core 2 O-glycans 1. This enzymatic activity is essential for synthesizing core 2 O-glycans that serve as scaffolds for selectin ligand sialyl Lewis X epitope display by myeloid cells, impacting inflammatory cell recruitment 2. GCNT1 also participates in glycolipid modification and SSEA-1 determinant synthesis. In disease contexts, GCNT1 is significantly upregulated in prostate cancer tissues and is controlled by androgen receptor signaling 3. Elevated GCNT1 expression correlates with altered O-glycosylation of cancer-associated proteins (PSA, MUC1, PAP) and serves as an independent predictor of biochemical recurrence after radical prostatectomy 4. GCNT1 expression in prostate biopsies indicates aggressive disease and extracapsular extension 5, with detectable levels in post-DRE urine identifying high-risk patients. Mechanistically, GCNT1-mediated glycosylation promotes tumor growth through altered oncogenic gene expression pathways 6. Beyond cancer, GCNT1 deficiency increases tuberculosis susceptibility through neutrophil dysregulation 7. Additionally, GCNT1 biosynthesis dynamically controls Siglec-7 ligand expression on T-cells, regulating immune cell activation 8. These findings establish GCNT1 as a crucial modulator of aberrant glycosylation in disease and a promising biomarker and therapeutic target.