In fact, in vitro and in vivo studies demonstrated that the treatment of ER+ breast cancer cells with α-methyl-DL-tryptophan (α-MT), which is a selective blocker of SLC6A14, reduces tumour growth by starving the cells of glutamine, arginine, and essential amino acids, inhibiting mTOR and causing apoptosis and autophagy [157]. This evidence concerns the gene SLC6A14 and breast cancer.