Figure 1.

TRAIL-induced apoptosis of six gastric cancer cell lines. (A) TRAIL-induced reduction of cell viability of six gastric cancer cell lines. Cells were seeded in 96-well plates one day prior to TRAIL treatment at 0, 6.25, 12.5, 25, 50 and 100 ng/ml for 24 h and 48 h. Cell viability was assessed by MTT assay and relative cell viability was calculated against untreated control. Data shown is the mean ± standard error (SE) of three independent experiments. P values were calculated from one-way ANOVA. (B) Six gastric cancer cell lines were treated with TRAIL at 25 ng/ml for 24 h, and then TRAIL-induced apoptosis was determined by flow cytometric analysis of Annexin V/PI binding. Right panel shows fractions of Annexin V positive and negative cells, respectively. * for P<0.05 calculated by Student's t-test. (C) Activation of caspases-3, -8 and -9 was examined by detection of procaspases and active caspase fragments in western blot analysis with whole-cell lysate preparation from indicated cell lines treated with TRAIL at 25 ng/ml for 24 h. (D) Expression of death receptors and apoptosis modulators in untreated and treated cells with TRAIL (25 ng/ml) for 24 h were examined by western blot analysis. (E) Surface expression of DR4 and DR5 in untreated and treated cells with TRAIL (25 ng/ml) for 24 h were analyzed by flow cytometry. Results shown are representatives of three independent experiments (B, C, D and E).