GALNT8 (polypeptide N-acetylgalactosaminyltransferase 8) catalyzes the initial step of O-linked oligosaccharide biosynthesis by transferring N-acetyl-D-galactosamine residues to serine or threonine residues on protein receptors, a process occurring in the Golgi apparatus 1. This glycosylation reaction is fundamental to protein post-translational modification and cellular function. In disease contexts, GALNT8 dysregulation associates with multiple pathologies. Missense mutations in GALNT8 are predicted to be highly deleterious and contribute to metabolic disorders including tumor calcinosis and hyperostosis-hyperphosphatemia syndrome 2. Paradoxically, GALNT8 expression patterns vary by cancer type: it acts as a tumor suppressor in breast cancer by suppressing EGFR O-GalNAcylation, thereby inhibiting epithelial-mesenchymal transition and metastatic potential 1. Conversely, GALNT8 overexpression driven by lncRNA GAU1 promotes colorectal and breast cancer progression through enhanced cell proliferation 3. In chr12 hepatitis C, GALNT8 variants affect interferon response by attenuating interferon-α-induced gene transcription 4. GALNT8 also associates with cortical thickness changes in Alzheimer's disease through protein-protein interactions with B4GALNT1 5. Clinically, GALNT8 expression levels serve as prognostic biomarkers and potential therapeutic targets across multiple cancers, with combined GALNT8/C1GALT1 overexpression predicting reduced survival in breast cancer patients 6.