SATB1 restoration sensitizes Sézary cells to AICD. SATB1-transduced and control clonal Hut78 cells were cultured with IL-2. Primary peripheral CD4⁺ T cells and CD4⁺CD7⁻ Sézary cells were stimulated by phytohemagglutinin and cultured in the presence of IL-2 for 6 days. All cells were restimulated with either plate-bound anti-CD3 antibody or PMA/ionomycin to trigger AICD. Specific apoptosis, which represents the increased apoptosis population after stimulation, was analyzed with annexin V binding-based apoptosis assay and compared. Proportions of annexin V⁺ population are indicated as no. (%). (A) On anti-CD3 antibody restimulation, SATB1-transduced Hut78 cells revealed increased specific apoptosis in contrast to the control Hut78 cells. The level of specific apoptosis in SATB1-transduced Hut78 cells was comparable with that in primary normal CD4⁺ T cells, whereas the level in control Hut78 cells was comparable with primary Sézary cells, which presented SATB1 expression defect. *P < .05 by Mann-Whitney U test. (B) On PMA/ionomycin restimulation, SATB1-transduced Hut78 cells and primary CD4⁺ T cells also revealed increased specific apoptosis in contrast to the control Hut78 cells, or primary Sézary cells. *P < .05 by Mann-Whitney U test. Hut78 indicates parental untransduced Hut78 cells; MIG-1 to MIG-3, Hut78 cell clones transduced with empty MIG vector; SATB1-1 to SATB1-4, Hut78 cell clones transduced with MIG vector containing SATB1; CD4+-1 and CD4+-2, primary peripheral CD4⁺ T cells; and SS, primary CD4⁺CD7⁻ T cells purified from Sézary patient.