CD274 and breast cancer: To this aim, MDA-MB-231, a human breast cancer cell line, and A-549, a human alveolar basal epithelial adenocarcinoma cell line, that express higher levels of PD-L1 and 5T4, were co-cultured with hPBMCs (3:1 effector/target ratio) and incubated at 37 °C for 48 h or 72 h in the absence or presence of 53D, 53 G, and 53L10.