CD274 and cancer: Currently, five validated commercial antibody-clones for PD-L1 testing have been approved by the FDA; each one is characterized by the specific binding sites to PD-L1 molecules and the antibody-based cancer therapy (22C3 for pembrolizumab, 28-8 for nivolumab, SP142 for atezolizumab, SP263 for durvalumab, and 73-10 for avelumab) [26].