Studies on a selective cyclooxygenase-2 inhibitor celecoxib inhibiting growth of human hepatocellular cancer SMMC-7721 cells lines and inducing apoptosis

Background and purpose:The incidence of hepatoma is high. The outcome of treatment on hepatoma is poor.So we investigated the effect and mechanism of a selective cyclooxygenase-2 inhibitor celecoxib on the proliferation and apoptosis of SMMC-7721 hepatoma cell line. Methods:MTT assay was used to study the inhibitive effect of celecoxib on the growth of SMMC-7721 hepatoma cell. The effect of celecoxib on cell cycle and apoptosis on cells was studied by flow cytometry(FCM).Transmission electron microscopy (TEM) was used to display the morphological change of the SMMC-7721 hepatoma cell . The biochemical character of apoptosis was viewed on the agarose gel electrophoresis.The expression of bax gene and bcl-2 gene were measured by immunohistochemistry.Results:The SMMC-7721 cells were cultured in media that contained 25,50,75,100 μmol/L celecoxib,by means of MTT, the inhibition rate was(15±3)%,(34.6±2.4)%,56.8±1.0)%,(86.2±0.4)% respectively after 24 hours; but the inhibition rate was (33.4±0.7)%,(66.7±1.8)%,(76.1±2.4)%,(97.3±0.8)% respectively after 48 hours(P0.05). Under the inspection of TEM,most of SMMC-7721 cells displayed the typically morphological features of apoptosis,including cell shrinkage,condensation and fragmentation of nuclear chromatine,etc. The group treated with celecoxib had an apoptotic peak in DNA histogram of FCM , but the control group had none.Treated with 50 μmol/L celecoxib, the apoptotic rate was (14.6±1.1)% after 24 hours. The apoptotic rate was (40.5±2.0)%、(56.2±1.4)%, respectively, treated with 100μmol/L celecoxib after 24 and 48 hours(P0.01). DNA ladder was viewed on the Agarose gel electrophoresis. It was observed by Immunohistochemical staining that celecoxib downregulated expression of bcl-2 gene, but upregulated the expression of bax gene.Conclusions:The celecoxib inhibited the proliferation and induced the apoptosis of the SMMC-7721 cells in a dose and time dependent way. The possible mechanism may be via the reduction of the expression of bcl-2 gene, but with increase of the level of bax gene, through which induced the human hepatoma cell apoptosis by the Mitochondria/Cyt C pathway.