Tpl-2 modulates the expression of the angiogenic factor COX-2. (A) LMP1 and Tpl-2 expression in HEK 293 cells transduces signals leading to COX-2 up-regulation. Cells were transfected with increasing amounts of LMP1, Tpl-2, or GFP-expressing vectors as indicated and 36 h later total lysates were analyzed for COX-2 or β-actin expression by immunoblotting. (B) Catalytically inactive Tpl-2 inhibits the ability of LMP1 to induce COX-2 expression. HEK 293 cells were transfected with 10 μg of LMP1 in the absence or presence of increasing amounts of Tpl-2[K167M] as indicated, and 36 h later total lysates were analyzed for COX-2 or β-actin expression by immunoblotting. (C) Tpl-2[K167M] suppresses LMP1-induced COX-2 promoter activity. HEK293 cells were cotransfected with 0.6 μg of COX-2 promoter-luciferase reporter construct, 0.2 μg of Renilla plasmid, 2.5 μg of pSG5-LMP1, and increasing amounts of Tpl-2[K167M], as indicated. The fold increase in RLVs (ratio of luciferase versus Renilla values) is shown.