ABSTRACT
Objective To study the effect and related mechanism of celecoxib on tumor necrosis factorrelated apoptosis-inducing ligand(TRAIL) induced apoptosis of medullary thyroid cancer TT cell line.Methods MTT assay was used to measure the growth inhibition induced by TRAIL and celecoxib alone and their combination.TT cell cycle distribution was analyzed by flowcytometry.Hochest33258 staining and DNA ladder was used to detect the apoptosis of drug combination on TT cells.Western blot was used detect the protein change of cyclin A,Cdk2,caspase-8,c-FLIP,and RIP.Results ①MTT showed the growth inhibition ratio of TT cell intervened by the combination of TRAIL and celecoxib was 47.53％ ± 1.34％,which was much higher than that intervened by TRAIL(7.75 ％ ± 3.84％)and celecoxib alone.The differences had statistical significance (t test,F =5.234,P ＜0.01);②PI detection found the cells' number in G0/G1 phase in celecoxib group and combination group were increased compared to that in control group and TRAIL group(F =242.694,P ＜ 0.01);③Western blot indicated the expression of Cyclin A and Cdk2 were down regulated,there was no statistic significance;④ The apoptosis morph in nuclus was detected by Hochest33258 staining and showed the karyopycnosis and muclear fragmentation were increased in combination group with the apoptosis rate 24.23％ ± 2.91％,which was much higher than that in TRAIL(5.86％ ± 1.41％) and celecoxib(20％ ± 1.24％) (t test,F =1.824,P ＜0.01),the difference has statistic significance;⑤Western blot illustrated the active schizolysis of casplase-8 was higher and the expression of c-FLIP and RIP was down regulated in combination group.Conclusion celecoxib plays a positive effect on TRAIL-reduced apoptosis of medullary thyroid cancer TT cell line,which may due to the cell cycle arrest at G0/G1 phase,down-regulation of c-FLIP and RIP and subsequent activation of caspase-8.