Abstract： Objective To investigate the regulatory effects of PTEN-PI3K/AKT pathway on the apoptosis of gastric cancer MKN28 cells and the possible mechanisms.Methods The specific sequence of PTEN was transfected to MKN28 cells by eukaryotic expression vector (transfection group),and then vacant vector (negative control group) and PBS (blank control group) were transfected to the MKN28 cells,respectively.The effects of PTEN-PI3K/AKT pathway on the apoptosis of MKN28 cells and the expressions of PI3K,AKT,Caspase-3 and Caspase-9 were investigated.The growth curve and apoptosis of the MKN28 cells were detected by MTT assay and TUNEL staining,respectively,and the protein expression was detected by the Western blot.MKN28 cells which did not transfected by the PTEN were processed by inhibitor of PI3K (LY294002) (treated group),and MKN28 cells in the control group were processed by PBS.The expressions of apoptosis protein and apoptosis-related protein were detected after inhibition of PI3 K.All data were analyzed using the t test.Results The model of over-expression of PTEN was obtained and transfected into MKN28 cells.The survival of MKN28 cells in the transfection group was significantly inhibited in a time-dependant manner ( r =0.938,P ＜ 0.05 ).The mean apoptotic rate of the transfection rate was 27.86％ ± 4.78％,which was significantly higher than 0.01％ ± 0.01％ of the negative control group ( t =9.527,P ＜ 0.05 ).The protein expression of PI3K in the transfection group was 0.25 ± 0.03,which was significantly lower than 0.93 ± 0.16 of the blank control group and 0.96 ± 0.15 of the negative control group (t =7.235,8.883,P ＜ 0.05 ).The protein expression of P-AKT in the transfection group was 0.21 ± 0.03,which was significantly lower than 0.93 ± 0.13 of the blank control group and 0.91 ± 0.12 of the negative control group (t =9.347,9.802,P ＜ 0.05 ).The expressions of Caspase-3 and Caspase-9 of the transfection group were 0.86 ± 0.11 and 0.87 ± 0.12,which were significantly higher than 0.16 ± 0.03 and 0.18 ± 0.04 of the negative control group,and 0.15 ± 0.02 and 0.16 ± 0.03 of the blank control group ( t =10.634,10.999,9.448,9.942,P ＜0.05).The apoptotic rate of the MKN28 cells of the treated group was 28.60％ ± 4.50％,which was significantly higher than 0.12％ ± 0.06％ of the control group (t =10.961,P ＜ 0.05 ).The protein expression of PI3K and P-AKT of the treated group were 0.18 ± 0.02 and 0.11 ± 0.01,which were significantly lower than 0.93 ± 0.14 and 0.90 ± 0.12 of the control group (t =9.186,11.363,P ＜ 0.05 ).The protein expression of PTEN of the treated group was 1.15 ± 0.15,which was significantly higher than 0.21 ± 0.08 of the control group (t =9.577,P ＜ 0.05 ).The relative expressions of Caspase-3 and Caspase-9 of the treated group were 0.86 ± 0.12 and 0.88 ± 0.11,which were significantly higher than 0.25 ± 0.02 and 0.21 ± 0.03 of the control group (t =8.685,10.178,P ＜ 0.05).Conclusions Over-expression of PTEN may enhance the apoptosis of gastric cancer cells through inhibition of PI3K/AKT pathway.Inhibition of PI3K can enhance the expression of PTEN.PI3K and PTEN regulate the apoptosis of gastric cancer cells.