CS-6 suppressed COX-2 expression. (A–C), Human A549, H322, H460 cells were treated with CS-6 at the indicated doses. At 48 h after treatment, expression levels of COX-2 protein and gene were analyzed by Western blotting (A), RT-PCR (B) and RT-qPCR (C) in A549 cells, respectively. (D) At 48 h after treatment, the COX-2 protein levels were analyzed by Western blotting in H322 and H460 cells. GAPDH was used as controls for sample loading. (E) A549 cells were pretreated with the COX-2-selective inhibitor celecoxib (CB, 25 uM and 50 uM) for 8 h and then treated with CS-6 (50 nM). At 48 h after treatment, cell viability was determined by MTT analysis. The percent cell viability was calculated relative to the cells treated with the DMSO vehicle control. The data are presented as the mean ± S.D. of three separate experiments. (*P < 0.05,**P < 0.01, significant differences between CS-6treatment groups and DMSO vehicle control groups). (F) A549 cells were pretreated with the COX-2 inhibitor celecoxib (CB, 50 uM) and inducer pyromellitic acid (PMA, 200 nM) for 8 h and then treated with CS-6 (50 nM). The protein levels of COX-2, the expression of cleaved caepase-3 were analyzed by Western blot.