SLC6A15 and cancer: Two other sodium-independent large amino acid transporters, SLC43A1 and SLC43A2 are also absent, leaving SLC6A15 encoding a known transporter of BCAA found in the mammalian brain, and SLC7A6, an antiporter exporting Arg and Lys in exchange for Leu, Ile and Gln also expressed in brain and cancers.