FIGURE 5.

Upregulation of DR5 depends on CHOP. (A,B,C) Caki-1 cells were treated with various concentrations of alternol for 24 h. Total cellular extracts were subjected to western blot analysis with indicated antibodies. (D) Caki-1 cells were transfected with PPARγ siRNA or scramble siRNA for 24 h. Cells were then treated with 20 μM alternol for an addition 24 h, and total cellular extracts were subjected to western blot assay. (E) Caki-1 cells were transfected with CHOP siRNA or scramble siRNA for 24 h. Cells were then treated with 20 μM alternol for an addition 24 h, and total cellular extracts were subjected to western blot assay. (F) Schematic structures of the DR5 promoter constructs used to measure luciferase activity. Mutations were introduced into the CHOP consensus sites. (G). Caki-1 cells were transfected with the reporter constructs, and lysates from cells that had been treated with various doses of alternol were assayed for luciferase activity. (H) Caki-1 cells were transfected with CHOP siRNA and scramble siRNA. Twenty-four h after the transfection, cells were treated alternol (20 μM), TRAIL (50 ng/ml), or their combination for an additional 24 h, and the apoptotic rate was determined by PI/annexin V staining. (I) After the treatment described above, cell viability was measured by MTT assay. (J) After the treatment described above, caspase-3/-8 activities were assayed. Data are the mean ± SD of three independent experiments. *p < 0.05; **p < 0.01; ***p < 0.001, compared with the untreated group.