ERBB2 and breast cancer: The take rate of breast cancer PDX engraftment is higher in NSG mice than in NOD/SCID mice21 because of lack of natural killer cells in the NSG strain.41 Indeed, the BEAUTY authors reported significantly higher PDX engraftment in NSG versus NOD/SCID mice.40,42 The overall take rate reported for TNBC in BEAUTY (all mice) was 51.3%; the take rate of TNBC or ER-low HER2– tumors in TOWARDS (NOD/SCID mice) was 27.4% (17/62).