fig4

Figure 4. Different secretion products from the A549BTZR cells did not trigger TRAIL sensitivity. (A) Western blot analysis was used to detect the basal expression levels of caspase-1, -4 and -5 in A549 and A549BTZR cells; (B) Supernatant of the A549 and A549BTZR cells was used to determine the cytokine secretion. The cytokine secretion levels detected in the A549BTZR supernatant were compared with the secretion by A549 cells, which was set to 1 (calculated from the means); (C) Cell death (subG1) was measured in A549 cells exposed to 100 ng/mL TRAIL for 24 h in supernatant collected from the H460 and A549BTZR cells. As a control, H460 and A549BTZR cells were exposed to 100 ng/mL TRAIL for 24 h in fresh medium; (D) Cell death (SubG1) in the H460 and SW1573 cells was determined after exposure to 100 ng/mL TRAIL for 24 h in culture medium or supernatant collected from A549 cells. The values are the means ± SEM of at least three independent experiments, while the blots are representative of at least 3 separate experiments. The effect of TRAIL treatment on H460 and A549BTZR cells on induction of apoptosis (C and D) was significant (P < 0.001). TRAIL: TNF-related apoptosis-inducing ligand; TNF: tumor necrosis factor.