PDCD1 and central nervous system cancer: Increased PD1/PDL1 expression in tumor tissues promotes the immune escape of tumor cells.49,50 Therefore, new anti-tumor immunotherapies based on PD-1/PD-L1 immunosuppressants have achieved good clinical results in melanoma tumor.51 However, the efficacy of PD1/PDL1 inhibitors in glioma clinical trials is considerably lower than that in other tumors, and they have substantial toxicity and side effects.52 The bottleneck of this treatment is mainly due to the limited expression and regulatory mechanism of PDL1 in gliomas.