Interestingly, with the aim to investigate the effect of immunotherapy on osteosarcoma, Zheng et al. showed that nivolumab inhibited osteosarcoma metastasis to the lung in humanized PBMC-engrafted mice injected with KHOS cells, promoting CD4+ and CD8+ lymphocyte infiltration and increasing the cytolytic activity of CD8 lymphocytes in the lungs, but did not affect the growth of the primary tumor, suggesting that the efficiency of immunotherapy may be organ specific [85]. The gene discussed is CD4; the disease is osteosarcoma.