Effect of FVIIa on IL-8 mRNA stability and gene transcription. (A) MDA-MB-231 cells were first treated with a control vehicle or FVIIa (50 nM) for 75 minutes. Then 10 μg/mL actinomycin D was added to inhibit RNA synthesis. Total RNA was harvested at indicated times after the addition of actinomycin D and was subjected to Northern blot analysis using IL-8 probe. IL-8 mRNA levels measured 10 minutes after the addition of actinomycin D were taken as 100% (mean ± SEM, n = 3). (B) Nuclei were isolated from unstimulated MDA-MB-231 cells or cells stimulated with FVIIa (50 nM) for 1 hour. Two identical blots containing β-actin and IL-8 DNAs were hybridized with equal amounts of labeled transcripts of nuclear RNA. (C) Quantitative representation of the data shown in panel B (mean values of 2 experiments).