IDH2^R172 mutations are associated with DNA hypermethylation in AITL and T cells. (A-B) Simultaneous detection of 5mC and 5hmC in transduced Jurkat cells by the LC-MS/MS method. (C-D) Simultaneous detection of 5mC and 5hmC in transduced human CD4⁺ T cells by the LC-MS/MS method. (E) LC-MS/MS showing alteration of intracellular 2-HG in corresponding groups (n = 4 each). (F) RRBS showing alterations of methylation level among normal tissues (n = 7, 3 tonsils and 4 CD4⁺ T-cell samples), IDH2 wild-type AITL (n = 8) and IDH2^R172 mutant AITL (n = 10) in different genomic regions. Promoters are ±1-kb regions relative to transcription start site. Gene bodies are regions of transcribed sequences excluding promoter regions. Intergenic regions are the sequences other than promoters and gene bodies. (G) RRBS showing alterations of methylation level in CpG island (CGI), CpG island shore (CGS), and non–CGI-CGS regions. (H) Number of hypermethylated genes in IDH2 wild-type AITL (n = 8) and IDH2^R172 mutant AITL (n = 10) compared with normal tissues. Red indicates genes only hypermethylated in IDH2^R172-mutant AITL. Green indicates genes only hypermethylated in IDH2 wild-type AITL. Blue indicates genes hypermethylated in both IDH2^R172 mutant and IDH2 wild-type AITL. Genes with expression data were divided into deciles based on the mean gene expression level of 5 normal CD4⁺ T-cell samples (10 = highest). Data are shown as mean ± SEM. P value was calculated using the 2-tailed Student t test. *P < .05, **P < .01, ***P < .001, and ****P < .0001.