TRAIL pretreatment does not affect TNF-α-induced NF-κB activation. HUVECs were either left untreated or pretreated with TRAIL for 3 days before stimulation with TNF-α. (A) NF-κB-p65 and NF-κB-p50 DNA-binding activity was determined at the indicated time points as absorbance values and is expressed as percentage of untreated control. ▪ indicates TNF-α; ▨, pretreated with TRAIL. (B) Analysis of surface leukocyte adhesion molecules (VCAM-1, ICAM-1, E-selectin) was performed by flow cytometry and is reported as mean fluorescence intensity (MFI). Results are expressed as means ± SD of 3 (for panel A) or 8 (for panel B) independent experiments.