To test the binding of PD-L1-specific ICIs, we used the tumor cell lines squamous cell carcinoma 1 (SCC1), canine oral squamous cell carcinoma (CoSCC) and immortalized dog uterine stromal cell line (DUS), none of which appeared to express cPD-L1 under normal culture conditions. This evidence concerns the gene CD274 and oral cavity squamous cell carcinoma.