Fig. 4. FGF2 does not trigger STAT transcriptional activity. (A) Growing RCS chondrocytes were treated with FGF2 for the indicated times and cell nuclei were isolated and analyzed for active STAT1 (upper graph) or STAT3 (lower graph) by STAT ELISA-based EMSA assay as described in the Materials and Methods. STAT activation was quantified by spectrophotometry. Note that FGF2 did not significantly elevate active nuclear STAT1 or STAT3. Rather, a diminution of basal active nuclear STATs appeared with prolonged FGF2 treatment. The data represent an average from two samples with the indicated range. The dashed line indicates basal STAT nuclear activity. Cells treated for 30 minutes with IFN or IL6 serve as positive controls for STAT activation. (B) RCS chondrocytes were transfected with three different STAT firefly luciferase (F-Luc) reporter vectors and a control Renilla luciferase (R-Luc) vector, stimulated with FGF2, IFN or IL6 for 72 hours and analyzed for luciferase activity as described in the Material and Methods. Data represent an average from four wells with indicated standard deviation. Statistically significant differences relative to control are indicated (Student's t-test; ^**P<0.01).