To validate the data obtained with the methylation arrays we used bisulfite pyrosequencing to analyze the DNA methylation and hydroxymethylation status of two CpG sites located at intron 2 of TET2 (cg12306086 and cg20586654) in the same samples analyzed in the methylation arrays, as well as in additional glioblastoma cell lines (see material and methods). The gene discussed is TET2; the disease is glioblastoma.