For example, Kraus et al. reported that (i) 5hmC concentrations in brain tumors were distinctly decreased compared with those in normal brain tissues; (ii) levels of 5hmC correlated with WHO grade of brain tumors; (iii) 5hmC levels were associated with isocitrate dehydrogenase 1 (IDH1) mutations in diffuse and anaplastic astrocytomas but not in glioblastoma multiforme (GBM) [23]. This evidence concerns the gene IDH1 and glioblastoma.