Some DNA hypomethylation was appreciated but due to the small sample size this was not significant and this data is consistent with a larger study of 112 matched primary (IDH wild-type) GBM patients comparing initial tumor to recurrent tumor by Klughammer and colleagues (23); this group, using a different technique, reduced representation bisulfite sequencing, found additional loss of DNA methylation in some promoters of recurrent tumors, but no significant global hypomethylation in recurrent GBM. Here, IDH1 is linked to glioblastoma.