SLC7A5 and breast cancer: Although SLC7A5 is a systemic L-amino acid transporter that carries branch-chain amino acids such as leucine and bulky amino acids such as glutamine, which are considered master regulators of the mTORC1 signaling pathway17,18, the mechanism by which SLC7A5 affects the prognosis of Erα-positive breast cancer patients is not yet fully understood.