FIG. 6.

Pretreatment with PT blocks FGF-stimulated MAPK activity. MM14 cells cotransfected with pFR-Luc, pFA-Elk1, and CMV-LacZ expression vectors were starved for 6 h in medium supplemented with 2.5% serum and no FGF-2. The cells then were stimulated with 0.1 nM FGF-2 for 6 h. Pretreatment included incubation with PT (192 pM) and CT (11.9 nM) 1 h prior to addition of FGF-2. Forskolin was added 15 min prior to FGF-2 addition. Control cells (with or without FGF-2) were incubated in the presence or absence of 0.1% dimethyl sulfoxide (not shown). Cells were harvested and normalized values of luciferase activities were determined 6 h following FGF-2 addition. Luciferase activity relative to activity in unstimulated cells is shown. Mean values and standard deviations represent three independent experiments performed in triplicate.