PDCD1 and central nervous system cancer: In glioma, we analyzed the correlation between SHOX2 expression level and ICP genes (Ligands and receptors), and the results showed that SHOX2 expression was positively correlated with many ligands and receptors, such as CD274, PDCD1LG2, BTLA, CD86, ICOSLG, CD70, PVR, CD40LG, CD244, CD226, HAVCR2, CD27, CD40, CD96, CD200R1, TNFRSF9, ICOS, PDCD1, CTLA4 and TNFRSF14 (Fig. S3).