CXCR4 and central nervous system cancer: In the TCGA database, co-expression analysis of hub genes with chemokines and related receptors also showed a regular pattern, with CXCL16 as a chemokine as well as CXCR4 and CCR5 as receptors negatively correlated (all P < 0.05, r < − 0.3) with all hub genes in glioma (Fig. 7A).