As a preliminary test of the hypothesis that PD-L1 may be a therapeutic target for the treatment of canine tumors, we investigated the effects of blockade of PD-1/PD-L1 by PD-L1 antibody in tumor-infiltrating T-cells from dogs with seminoma, hepatocellular carcinoma and myelolipoma. This evidence concerns the gene CD274 and hepatocellular carcinoma.