SLC16A9 (solute carrier family 16 member 9) functions as a dual-specificity transporter with distinct physiological roles. Primarily, it operates as an extracellular pH- and Na+-sensitive low-affinity creatine transporter and as a pH-independent carnitine efflux transporter 12. The protein facilitates carnitine transport across cell membranes, with genetic variations in SLC16A9 significantly affecting plasma carnitine levels 3. In cancer biology, SLC16A9 expression is epigenetically regulated by the PKM2-EZH2 complex, where its de-repression increases intracellular carnitine influx and promotes a metabolic switch from glycolysis to fatty acid β-oxidation in triple-negative breast cancer cells 4. The transporter shows tissue-specific expression patterns and has been implicated in various pathological conditions. In hepatitis B treatment, SLC16A9 genetic variants are associated with HBsAg loss, potentially through effects on CD8 T cell proliferation via carnitine-mediated mechanisms 3. Additionally, SLC16A9 has been identified as a biomarker in dilated cardiomyopathy, periodontitis, and colorectal cancer progression 567. The gene's role in urate metabolism has also been recognized through genome-wide association studies 8.