PDCD1 and central nervous system cancer: In the TCGA database, co-expression analysis of hub genes with ICGs showed a regular pattern, with CD276 (B7H3), PDCD1, LAG3 being negatively correlated (all P < 0.05, r < − 0.3) with all 3 hub genes in glioma, while TIGIT was not associated robustly (Fig. 6A).