CD274 and cancer: Among the immune checkpoint inhibitors (ICIs) developed so far, pembrolizumab and nivolumab that target PD-1/PD-L1 have shown promising therapeutic potentials with high objective response rates (ORR) in a variety of cancers including melanoma and non-small cell lung carcinoma, urothelial bladder cancer, and triple-negative breast cancer (Darvin et al., 2018).