SLC22A16 (CT2) is a facilitative organic cation transporter that mediates bidirectional, partially sodium-dependent transport of carnitine and the polyamine spermidine 12. In testicular tissue, SLC22A16 facilitates carnitine secretion from epididymal epithelium into the lumen, supporting spermatozoa maturation 1. The transporter also functions in drug transport, serving as an adriamycin importer 3 and influencing doxorubicin pharmacokinetics in cancer patients 4. Recent evidence demonstrates SLC22A16's role in maintaining carnitine and acyl-carnitine pools in aging red blood cells, where genetic variants (rs12210538) affect lipid damage repair and hemolysis 5. In leukemia stem cells, SLC22A16-mediated drug endocytosis contributes to chemotherapy-induced senescence when PSMB10 is inhibited, offering a potential therapeutic strategy for overcoming drug resistance 6. SLC22A16 genetic polymorphisms exhibit interethnic variation and influence doxorubicin exposure in breast cancer patients, though associations with chemotherapy toxicity remain inconclusive 47. The transporter can be functionally expressed in bacterial systems for biochemical characterization 8. Mutations in SLC22A16 and related carnitine transporters cause primary carnitine deficiency with pathological effects on muscle and brain function 9.