CXCR4 and central nervous system cancer: Previous gene expression studies identified CXCR4 as one of the most down-regulated genes in H3 K27M glioma as compared to H3 K27 wild-type pediatric high-grade gliomas.8 Likewise, FOXG1 was identified as having near maximal JSD among the primary samples and has been implicated as one of the most down-regulated genes in histone mutant glioma (Figure 4c).