Bid overexpression highly increases the apoptosis induced in RA FLS by membrane-bound FasL and caspase-9 cleavage after anti-Fas stimulation. (a) Cultured rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) were transfected as indicated in Figure 4 and treated for 12 hours with 100 ng/ml mFasL or pretreated for one hour with Wortmannine (Wort) or with Wort and the caspase-9 inhibitor, Z-LE(OMe) HD (O Me) FMK (LEHD), before Fas stimulation. Apoptosis, assessed by quantification of nucleosomal release, is shown and data represented the mean (standard error of the mean) of seven RA FLS different lines. (b and c) Transfected RA FLS were treated for 12 hours with 1 μg/ml anti-Fas antibody or pretreated for one hour with Wort before Fas stimulation. Caspase-9 cleavage was analysed by western blot. (b) A representative blot is shown. (c) Densitometric analysis of band intensity of cleaved caspase-9 normalized to full caspase-9 is shown. * indicates P < 0.05; # and † indicate P < 0.05 versus anti-Fas-only treatment.