Cells were exposed for 24 h to vehicle or ciglitazone at the indicated concentrations. (A) The percentage of cells showing the hypodiploid DNA content (sub-G1 peak) was evaluated by flow cytometry analysis. (B), (C) The cleavage of caspases 9, 8, 3 and PARP as well as the expression of pro- and anti-apoptotic proteins were determined by western blotting analysis. (D, left) Cells were preincubated 1 h with 50 µM caspase 8 (Z-IETD-FMK) or 9 (Z-LEHD-FMK) specific inhibitor before treatment with 40 µM ciglitazone for 12 h and assessment of caspases 8, 9, 3 and Bid processing was analysed by western-blotting. β-actin was used as an internal loading control ; (D, right) After indicated treatments, cells were stained with PI for DNA fragmentation analysis by flow cytometry. Data are means ± SD of 3 independent experiments performed in triplicates. *P<0.05, significant differences compared with untreated cells ; **P<0.05, significant differences compared with ciglitazone-treated cells with the use of two-tailed unpaired Student's t test.