While immune-inflamed ‘hot’ tumors have significant numbers of CD8(+) T cells in the tumor stroma and express pro-inflammatory cytokines, responding well to T cell immunotherapies, osteosarcoma belongs to ‘cold’ tumors characterized by the paucity of TILs, accompanied by immunosuppressive tumor infiltrating myeloid cells, such as TAMs and MDSCs, as well as regulatory T cells (Tregs) [118,119,120]. The gene discussed is CD8A; the disease is osteosarcoma.