Activation of caspase-8 during apoptosis of human colorectal cancer cell line SW480 induced by oxaliplatin

Objective To investigate the effect of oxaliplatin on human colorectal cancer cell line SW480 through up-regulated expression of caspase-8.Methods Methyl thiazolyl tetrazolium(MTT)assay was used to measure the proliferation of SW480 cells cultured with different concentrations of oxaliplatin for 24,36 and 48 h in vitro.Cell-cycle kinetics and apoptosis were analyzed by flow cytometry(FCM).The changes of pro-caspase-8,caspase-8 mRNA and relative activity of caspase-8 were analyzed by Western-blot,semi-quantitative RT-PCR,and colorimetric assay with PAN-labelled substrate,respectively.Results The proliferation of SW480 cells was significantly suppressed by oxaliplatin in a concentration-and time-dependent manner.The cell was arrested at G2/M and apoptosis was induced.When SW480 cells were treated with oxaliplatin at the concentration of 0,0.03,4.0 and 100 μg/ml,the apoptosis rates of SW480 cell were(0.15±0.09)%,(0.43±0.17)%,(6.92±0.81)% and(11.76±1.25)%,respectively.After SW480 cells were treated with 0,0.03,4.0 and 100 μg/ml of oxaliplatin for 24 h respectively,the level of pro-caspase-3 protein decreased and caspase-3 mRNA increased as concentration increased(P0.01).When cells were treated with oxaliplatin at the concentration of 4.0 μg/ml for 0.5,2,6,12 and 24 h,the caspase-8 activity began to rise at 2 h and reached the peak at 12 h(P0.01).After cells were treated with oxaliplatin of different concentrations for 12 h,caspase-8 activity increased in a concentration-dependent manner(P0.01).Conclusion Oxaliplatin can significantly inhibit the proliferation and induces G2/M arrest in human colon cancer cell line SW480.The mechanism is related to up-regulated expression of caspase-8.