4T1-Luc-HER2 cells were ideal HER2+/PDL1+ target cells, since the percentage of HER2-positive (87.8%) and PDL1-positive (95%) was high (Figures 1A,C), and the expression level of HER2 protein was at least as same as that of HER2-positive human breast cancer BT474 and SKBR3 cells (Figure 1B). This evidence concerns the gene ERBB2 and breast cancer.