High expression of immune checkpoint genes is associated with a better clinical prognosis, and we speculate that this may be because the immune system of osteosarcoma patients can efficiently recognize the tumor and develop an immune response, and because highly mutated genes in osteosarcoma does not produce sufficient neoantigens that can elicit an immune response so that targeted inhibition of PD-1/PD-L1 therapy in osteosarcoma is unsatisfactory. Here, PDCD1 is linked to osteosarcoma.