SLC46A3 and breast cancer: Indeed, the role of SLC46A3 loss in conferring resistance to T-DM1 has been demonstrated in the T-DM1–resistant BT-474M1 breast cancer cell line (BT-474M1 is a derivative subline of the human breast cancer cell line BT-474 and is widely employed as a well-characterized model of acquired T-DM1 resistance)[41].