CD274 and neoplasm: Then HER2.28ζ/PD-L1.BB, HER2.28ζ, PD-L1.BB CAR-T cells, or untransduced (UTD) T cells were co-cultured with different tumor cells (SKOV3PD-L1, A549, H1975, or MDA-MB-468) at various E: T ratios (1:2, 1:1, 2:1, and 4:1) for 24 h in a cytokine-free medium (culture medium).