Fig. 5. uPA-specific antibody inhibits the growth of MDA-MB-231 cells. (A) The indicated number of MDA-MB-231 cells was plated in 96-well plates, in triplicate, and cultured overnight. The cultures were then transferred into serum-free medium and incubated for 24 hours with uPA-specific antibody (+) or vehicle (-). Cell growth was determined by MTT assay. The number of viable cells in each culture prior to the 24 hour culturing period was determined as a control (labeled ‘C’). The asterisk indicates that antibody significantly altered cell growth compared with vehicle (unpaired t-test, P<0.05, n=3). (B) 4x10⁴ MDA-MB-231 cells were plated in 48-well plates, in triplicate, and cultured at 37°C for 24 hours. The cells were then incubated with increasing amount of uPA-specific antibody, PD098059 (10 µM) or mouse nonimmune IgG (25 µg/ml) for 30 hours. [³H]thymidine incorporation was measured. The asterisk indicates that the value is significantly different from the control (unpaired t-test, P<0.01, n=3).