CD274 and cancer: PD-1 has been intensely investigated due to this potent inhibitory function on the immune system, and mAbs targeting PD-1 or PD-L1, such as nivolumab, pembrolizumab, and atezolizumab, have been developed and used as single agents or in combination with chemotherapy or other immunotherapies, to augment antitumor cytotoxic T cell responses in cancer patients [173,174,175].