CD274 and cancer: A number of immune checkpoint inhibitors, including programmed cell death ligand 1 (PD-L1) or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies and agonists of costimulatory molecules have shown satisfactory results in clinics for the treatment of cancer patients, however, they still have a number of troublesome problems including low response rate, high cost and non-specific toxicity [3–5].