Global DNA hypomethylation occurs in cells infected with HTLV-1. (A) Representative flow cytometric analysis of PBMCs isolated from a patient with chronic ATL. P, CADM1⁻/CD7⁺ (blue); D, CADM1⁺/CD7^dim+ (yellow); N, CADM1⁺/CD7⁻ (red). (B) Proportion of each cell subpopulation (P, D, and N) in the CADM1 vs CD7 plots of healthy volunteers, asymptomatic carriers, and patients with smoldering, chronic, and acute ATL. (C) Unsupervised hierarchical clustering analysis of DNA methylation profiles of 20 000 CpG probes chosen at random from 470 870 probes, which were CpG sites on autosomes and not on the sex chromosomes, and non-CpG probes. yHC, young healthy volunteer; aHC, aged healthy volunteer; AC, asymptomatic carrier; S, smoldering ATL; C, chronic ATL; A, acute ATL. DNA methylation analysis of HTLV-1–infected cell lines (MT-2, ST-1, KOB, KK-1, and ATN-1) was performed without sorting because the CADM1/CD7 expression pattern indicated that they were single-cell populations. (D) Average β values of the 470 870 probes in each cell subpopulation from individuals and HTLV-1–infected T-cell lines. Differences between each subpopulation were tested using the Tukey-Kramer method. *P < .05.