The immunoreceptor tyrosine-based activation motif of the K1 protein and Lyn kinase activation are required for K1-induced NF-κB activity and VEGF production. (A). BJAB-K1, BJAB-K1m, and BJAB-XS cells were transfected with 5μg NF-κB–luciferase reporter construct. After 24 hours, the cells were harvested for luciferase activity (□), and VEGF in culture supernatants (▪) was quantified as described in “Materials and methods.” Results represent the means (± SD) of 3 experiments. There were statistically significant decreases in NF-κB promoter activity (^*P < .001) and VEGF production (†P < .001) in BJAB-K1m and BJAB-XS cells compared with BJAB-K1 cells. (B) BJAB-K1, BJAB-K1m, and BJAB-XS cells (2 × 10⁶) were transfected with 5 μg of a human VEGF promoter–luciferase construct. After 20 hours, the cells were treated with PP2 (13 μM; ▪) or not (□) for 4 hours and harvested for a luciferase assay as described in “Materials and methods.” Results represent the means (± SD) of 3 experiments. Statistically significant decrease (^*P = .005) in VEGF promoter activity versus no treatment with PP2 was observed in BJAB-K1 cells.