DUSP5 expression is silenced in HTLV-1–infected T cells during ATL leukemogenesis. (A) DUSP5 expression in healthy volunteers and patients with ATL was analyzed using GSE33615. Normal CD4⁺ T cells were isolated from healthy volunteers (n = 21). PBMCs were isolated from patients with smoldering (n = 4), chronic (n = 20), and acute (n = 26) ATL. Differences between normal and each ATL subtype were tested using Steel test. (B-C) HTLV-1–infected T cells (CADM1⁺ T cells) and normal counterparts (CD7⁺CADM1⁻ T cells) were isolated from healthy volunteers (n = 3), HTLV-1 carriers (n = 1), and patients with smoldering ATL (n = 4) and chronic ATL (n = 2). DUSP5 expression was measured by western blotting and normalized to β-actin. Left panel: the ratio of DUSP5 expression in CADM1⁺ cells compared with paired CADM1⁻ cells. Differences between each cell were tested using the paired t test. (D) DUSP5 expression was compared between HTLV-1–infected cell lines and CD3⁺CD4⁺CD7⁺CADM1⁻ T cells (normal T cells) from 2 healthy volunteers. (E) DUSP5 protein expression in HTLV-1–infected cell lines was determined by western blotting. (F) Location of CpG sites analyzed using GSE136189 (red line) and H3K27me3 peaks analyzed using GSE71450 (blue line) around the DUSP5 promoter region. The green line indicates CpG islands. (G) β-values of TSS1500-shore CpG sites of DUSP5 in CD7⁺CADM1⁻ T cells (subpopulation P), CD7⁺CADM1⁺ T cells (subpopulation D), and CD7⁻CADM1⁺ T cells (subpopulation N) of healthy volunteers, HTLV-1 carriers, patients with ATL, and ATL cell lines. The site was located in TSS1500-shore, as shown in supplemental Table 4. (H) H3K27me3 alternations of the 10 promoter regions in DUSP5 in patients with ATL (n = 3) compared with healthy volunteers (n = 2). The numbers of y-axis indicate distances from TSS, as shown in supplemental Table 5.