CTLA4 and central nervous system cancer: Furthermore, the differential expression of PD-L1 and CTLA-4 were compared between lower-grade gliomas (LGGs; tumour grade II ∼ III) and glioblastoma in the high-risk group, and between different risk groups within the same tumour grade, such as PD-L1-grade IV-Low risk V.S. PD-L1-grade IV-High risk.