CD274 and breast cancer: These novel combinations were tested on PD-L1-positive MDA-MB 231 and BT-549 breast cancer cells expressing 5T4, co-cultured for 48 h with lymphocytes (Effector:Target cells ratio 5:1), by using the Tb535H tribody (1 nM) plus each of the immunomodulatory mAbs (50 nM) in comparison with each single parental compound (Supplementary Fig. 1A and B).