In the next step, we determined the immune infiltration of the osteosarcoma clusters using the ssGSEA package and obtained 28 immune cells in osteosarcoma samples; as expected, cluster 3 was detected with a higher number of immune cells, such as monocytic lineage, T cells and CD8+ T. Previously, it has been suggested that most tumors at an advanced stage may have a higher frequency of mutations in genes related to the tumor immunity as compared to the early-stage tumors, which can activate more T cells and produce a stronger immune response (Ren et al., 2021). The gene discussed is CD8A; the disease is osteosarcoma.