PI3 kinase inhibition sensitizes RA FLS to Fas-induced apoptosis. Cultured rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) were untreated (Basal), treated for 12 hours with 1 μg/ml anti-Fas antibody or pretreated for one hour with phosphoinositol-3 (PI3) kinase inhibitors (Wortmannine (Wort) or LY294002 (LY)) before Fas stimulation. (a) Apopotosis was quantified by nucleosomal release ELISA assay. Changes in individual RA FLS lines are represented. * indicates P < 0.05 versus untreated cells; # indicates P < 0.01 versus anti-Fas-only treated cells. (b) Caspase 3/7 activity determined by a caspase 3/7-Glo assay. (c) Quantification of apoptosis in RA FLS by Hoetchst 33258 staining. For b and c, results are the mean (standard error of the mean) of six different RA FLS lines. * indicates P < 0.05 versus untreated cells and # indicates P < 0.05 versus anti-Fas-only treated cells. (d) Representative images of one experiment are shown.