Lastly, one group has made great progress in the detection of overexpression of PD-1 from TILs and PD-L1 from malignant tumors in several canine cancers, such melanoma, osteosarcoma, hemangiosarcoma, and others, in the interest of establishing a rationale for application of anti-PD therapeutics in dogs (136, 137). This evidence concerns the gene PDCD1 and melanoma.