fig3

Figure 3. Enhanced secretion of OPG by A549BTZR did not induce TRAIL sensitivity. (A) With the use of ELISA, the secreted OPG levels were measured in the supernatant of the different cell lines; ^*significantly different (P < 0.01). The secretion of OPG by both SW1573 variants was 0.41 pg/mL; (B) Cell death was measured in the TRAIL-resistant A549 and SW1573 cells after incubation with 900 pg/mL OPG for 4 h followed by the addition of 100 ng/mL TRAIL for 24 h. The effect of TRAIL was significantly higher than that of OPG (^*P < 0.01). The values are the means of at least three independent experiments ± SEM. OPG: Osteoprotegerin; TRAIL: TNF-related apoptosis-inducing ligand; TNF: tumor necrosis factor.