SLC7A5 (BCAA, Phe and Tyr transporter) is a prognostic factor for breast cancer (39) and is included in the Mammostrat prognosis prediction test for ER-positive breast cancer tumors (40); while, SLC6A14 (transporter of neutral and cationic amino acids) is highly expressed in ER-positive breast cancer tissue and cell lines, and its transcription is under Erα and MYC regulation (41). Here, ESR1 is linked to breast cancer.