Matrix Gla protein (MGP) is a vitamin K-dependent extracellular matrix protein with multifaceted biological functions extending beyond its classical role in calcification regulation. Originally identified as a physiological suppressor of ectopic calcification 1, MGP associates with bone and cartilage organic matrix and acts as an inhibitor of bone formation. Mechanistically, MGP functions through multiple pathways. In cancer contexts, MGP enriches intracellular calcium levels and promotes NF-κB phosphorylation, activating PD-L1 expression to facilitate CD8+ T cell exhaustion in colorectal cancer 2. In breast cancer lymph node metastasis, MGP expression on lymphatic endothelial cells is TGF-β and VEGF-dependent and promotes cancer cell adhesion to lymphatics 3. MGP also regulates endothelial cell phenotypes critical for muscle degeneration during aging 4. Clinically, MGP demonstrates prognostic significance across multiple malignancies. Altered MGP expression correlates with disease progression and overall survival in breast, kidney, liver, and thyroid cancers, suggesting utility as an independent prognostic indicator 5. Epigenetic regulation through promoter CpG methylation further influences MGP transcription in tumors 5. MGP genetic variants show weak associations with myocardial infarction risk in specific subgroups, with certain alleles associated with increased plaque calcification 6. Pathogenic GGCX mutations causing deficient MGP γ-carboxylation result in Keutel syndrome with mineralization defects and skeletal dysmorphologies 1.