CD274 and cancer: In order to better understand the impact of anti-cancer drug treatment on cancer cell-autonomous expression of PD-L1 in breast/mammary gland cancer, four breast cancer (BC) cell lines - representing both TNBC and ER + – were used; MDA-MB-231 and 4T1 represent TNBC in humans and mice, and MCF-7 and E0771 represent ER + BC in humans and mice.