Strong correlations were found between PD1 (PDCD1) and PDL1 (CD274)/PDL2 (PDCD1LG2), between CTLA4 and CD80/CD86, and between CXCR4 and CXCL12 in gliomas Additional file 4: Fig. 3a-c). Here, CXCL12 is linked to central nervous system cancer.