Objective    To observe the effect of diamminedichloroplatinum (DDP) and combined DDP and cyclooxygenase (COX-2) selective inhibitor NS-398 on proliferation and apoptosis of esophageal cancer Eca-109 cells in vitro and their anti-tumor effect.     Methods    CCK-8 assay was used to detect the inhibitory rate of DDP at the concentrations of 1.25

2.5

5

10

and 20 mg/L and combined DDP and NS-398 at the concentrations of 1.0 and 10.0 μmol/L for human esophageal cancer Eca-109 cells 24 h after they were used. Agarose gel electrophoresis was performed to show the DNA ladder of human esophageal Eca-109cancer cells in 24 h and 48 h after they were treated with DDP at the concentration of 1.25

2.5

and 5.0 mg/L

and combined DDP and NS-398 at the concentration of 1.0

10.0

and 80.0 mg/L. Transmission electron microscopy was employed to observe the ultra-structure of Eca-109 cells 24 h after they were treated with DDP and combined DDP and NS-398

respectively. Non-drug treated esophageal cancer Eca-109 cells served as a control group.     Results    Cell growth inhibition test showed that DDP and NS-398 inhibited the proliferation of esophageal cancer Eca-109 cells in a dosedependent manner (P0.05). The growth inhibition rate and apoptosis rate of combined DDP and NS-398 were significantly higher than those of DDP for esophageal cancer Eca-109 cells

indicating that DDP and combined DDP and NS-398 exhibited a synergistic effect on the proliferation and apoptosis of esophageal cancer Eca-109 cells.     Conclusion    The effect of DDP in combination with a low dose of NS-398 is stronger than that of DDP on the proliferation and apoptosis of esophageal cancer Eca-109 cells.