CD8A and osteosarcoma: Although no effect of nivolumab was observed on tumor growth in PBMC-humanized mice engrafted with osteosarcoma tumors, it partially inhibited lung metastases formation by the increase of CD4+ and CD8+ T lymphocytes and of CD8+ T cell cytolytic activity in the lungs (78), opening the door for anti-PD1 treatment in metastatic osteosarcoma patients (Figure 2A).