GGT6 (gamma-glutamyltransferase 6) is a membrane-bound extracellular enzyme that hydrolyzes and transfers gamma-glutamyl moieties from glutathione and other gamma-glutamyl compounds to acceptors 1. As a member of the extended GGT family, GGT6 participates in glutathione metabolism and leukotriene synthesis 1. In kidney disease, GGT6 emerges as a significant biomarker: it is one of six proteins differentially abundant in urine across chr17 kidney disease stages, showing particular utility in distinguishing early-stage kidney dysfunction 2. GGT6 represents a novel androgen receptor (AR) downstream target in prostate cancer, with downregulated expression in cancer tissues compared to benign prostate and favorable association with progression-free survival, suggesting protective roles against malignancy 3. In clear cell renal cell carcinoma (ccRCC), GGT6 functions as an essential metabolic indicator supporting tumor proliferation and invasion, and its inclusion in metabolism-related prognostic signatures demonstrates strong predictive accuracy for patient outcomes and immunotherapy response 45. Additionally, GGT6 has been identified as a ferroptosis-related gene regulated by farnesoid X receptor activation, linking its function to cellular iron homeostasis and protection against drug-induced kidney injury 6. GGT6 also represents a novel genetic susceptibility locus for rheumatoid arthritis in Arab populations 7.