AP-1 plays a critical role in isoproterenol-induced MMP-7 expression. A, schematic representation of the plasmid pMMP-7mA containing a mutated AP-1 site at the position -67 to -61. B, MGC-803 cells were co-transfected with pMMP-7mA and pRL-TK, starved and then stimulated with 10 μM isoproterenol for 0, 1, 2, 3, 6 or 9 h, respectively. MMP-7 promoter activities were assessed by luciferase assays. C, MGC-803 cells co-transfected with TAM67, pMMP-7 and pRL-TK were induced with 10 μM isoproterenol. MMP-7 promoter activities were analyzed by luciferase assays. D, MGC-803 cells stably expressing shRNA targeting c-Jun (MGC-803/c-Jun-sh) were established and c-Jun expression was analyzed by Western blot. E, MMP-7 promoter activities were assayed in MGC-803/c-Jun-sh cells after stimulation with 10 μM isoproterenol for 0, 1, 2, 3, 6 or 9 h, respectively. F, MMP-7 expression was analyzed in MGC-803/c-Jun-sh cells after stimulation with 0, 2 or 10 μM isoproterenol, respectively. G, the plasmids expressing c-Jun and STAT3C were transfected into MGC-803/c-Jun-sh cells, respectively. MMP-7 promoter activities were analyzed by luciferase assays.