CD274 and cancer: In a further study, we decided to focus on breast cancer models, as the expression of PD-L1 protein in this cancer significantly correlates with survival outcome in patients with mammary malignancies.9 10 Notably, our results of the variable expression of PD-L1 in breast cancer cell lines are in accordance with previous observations in primary mammary malignancies.11 Therefore, our data support the notion that a proportion of breast cancers, especially of triple-negative phenotype, could potentially be directly targeted by PD-L1–CAR.