Up-regulation of FasL expression and activation of FasL-induced apoptosis pathway in SATB1-transduced Hut78 cells. (A) RNA expression level of FasL in primary CD4⁺CD7⁻ Sézary cells and Sézary cell line Hut78 are significantly lower than that in normal CD4⁺ T cells. *P < .05 by t test. (B) RNA expression level of FasL was significantly up-regulated in SATB1-transduced Hut78 cells (Hut78-SATB1), compared with empty MIG vector-transduced cells (Hut78-MIG). **P < .01 by t test. (C) The protein expressions of SATB1, FasL, Fas, cleaved-caspase 8, and cleaved caspase 3 were analyzed by Western blot with specific antibodies. All SATB1-transduced cell clones revealed high expression level of SATB1, increased expression of FasL, cleaved caspase 8, and cleaved caspase 3, whereas the expression of Fas remained unchanged. GAPDH served as an internal reference. (D) SATB1-transduced and control clonal cells were incubated with exogenous super FasL to trigger Fas-mediated cell death. SATB1-transduced cells revealed comparable specific apoptosis rate with the control cells, which showed unaltered Fas function after SATB1 transduction. Hut78 indicates parental Hut78 cells; MIG-1 to MIG-3, clonal cells from Hut78 cells transduced with control MIG vector; and SATB1-1 to SATB1-4, cell clones from Hut78 cells transduced with vector containing SATB1.