Since IL-6 produced by glioma cells promotes PD-L1 expression of MDSCs, the immunosuppressive function of MDSC is suppressed by IL-6 KO or an anti-IL-6 antibody and the antitumor effect on glioma cells is enhanced by combination therapy using anti-PD-1 antibodies [108]. The gene discussed is PDCD1; the disease is central nervous system cancer.