Early genome-wide 5-mC analyses revealed that many low-grade gliomas and secondary GBMs contained large numbers of hypermethylated loci referred to as the glioma CpG island methylator phenotype (G-CIMP), and this was closely associated with the presence of somatic IDH1 mutations, and improved prognosis (35–37). This evidence concerns the gene IDH1 and central nervous system cancer.