Fig. 3. Caveolin-1 (Cav-1) knockdown in HCT-116 cells abolishes protection against tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Cav-1 expression was decreased ∼50% from basal levels 72 h after the small interfering RNA (siRNA) transfection (n = 4 for scrambled siRNA and n = 3 for Cav-1 siRNA). *P < 0.05 (A ). HCT116 cells treated with control scrambled siRNA were still resistant to TRAIL-induced apoptosis after isoflurane (n = 5) (B ). However, Cav-1 knockdown reversed this effect (n = 5) (C ). Western blot analysis and caspase activity assays confirmed these findings and revealed attenuated caspase 3 activation in cells treated with scrambled siRNA and exposed to isoflurane and TRAIL, but this protective effect was attenuated by Cav-1 siRNA (n = 5) (D and E ). *P < 0.05. Iso = isoflurane.