In the osteosarcoma microenvironment, MDM2 overexpression can inhibit the survival and effector function of CD8+ T cells, leading to the reduced the activity of tumor-infiltrating lymphocytes (TILs), and promoted macrophage polarization toward the M2 phenotype, thereby enhancing the immunosuppressive microenvironment. The gene discussed is MDM2; the disease is osteosarcoma.