CD274 and breast cancer: Based on flow cytometry analysis, we found that PD-L1 was highly expressed in multiple human tumor types, including breast cancer (MDA-MB-231), ovarian cancer (IGROV-1, OVCAR8, and NCI-ADR-RES), pancreatic cancer (KLM1 and SU8686), and lung cancer (EKVX), suggesting that PD-L1 is a putative pan-cancer antigen (Figure 3A).