SCG5 (secretogranin V) is a secretory granule protein that functions as a molecular chaperone for PCSK2/PC2 in the regulated secretory pathway, preventing premature activation and facilitating transport from the endoplasmic reticulum to later compartments where PCSK2 undergoes proteolytic maturation [UniProt]. The protein plays a role in regulating pituitary hormone secretion and peptide hormone processing through its interaction with inactive PCSK2. Beyond its canonical chaperone function, SCG5 has emerged as a significant biomarker in multiple malignancies. SCG5 is differentially expressed across various cancers, with elevated expression associated with tumor progression 1. In esophageal squamous cell carcinoma, high SCG5 mRNA expression correlates with decreased overall and disease-specific survival, and SCG5 knockdown suppresses cell invasion, proliferation, and migration in vitro and tumor growth in vivo 2. Similarly, in non-small cell lung cancer, elevated SCG5 predicts poor prognosis and serves as an independent prognostic factor 3. Conversely, in pancreatic adenocarcinoma, SCG5 is significantly reduced and decreased further with tumor progression, suggesting diagnostic and prognostic utility 4. The SCG5 rs4779584 polymorphism is associated with increased colorectal cancer risk 5. Additionally, SCG5 has been identified as a copper metabolism-related gene affecting Alzheimer's disease progression 6 and as part of multi-omic signatures predicting mortality in oral squamous cell carcinoma 7.