Effect Of Rapamycin Induced Autophagy On Apoptin Inhibition Of Xenograft Growth In Nude Mice With Human Gastric Cancer

Objective: Take human gastric cancer cell SGC7901(middle and low differentiation)and PMA-induced SGC7901 cells(poorly differentiated)as research objects.To investigate the effects of PTD4-apoptin protein on apoptosis and autophagy of gastric cancer cells with different degrees of differentiation at the animal level,and the tumor-inhibiting effect of PTD4-apoptin protein after autophagy intervention was observed.Method: The PTD4-apoptin proteins were obtained by induced expression and purification.The gastric cancer cell SGC7901 and low-differentiated gastric cancer cell SGC7901 were cultured.tumor transplantation model of human gastric cancer cell SGC7901 in nude mice was established.Effects of PTD4-apoptin protein and PTD4-apoptin(P4A)combined with Rapamycin(Rap),an autophagy inducer,on tumor in nude mice were detected.After successful modeling,20 nude mice with similar tumor tissue size and weight were selected and randomly divided into four groups,5 in each group,respectively PBS control group,P4 A group,Rap group and P4A+Rap group.PTD4-apoptin protein(P4A)was applied around and on the tumor body.PTD4-apoptin was given with intraperitoneal injection of Rapamycin(Rap)in the P4A+Rap group.Rapamycin was given to the Rap group alone;Only PBS group was treated as blankcontrol group.The day of administration was recorded as day 0.Tumor length and short diameter were recorded every three days,and tumor volume-time growth curve was drawn.After 15 days of administration,xenografts were removed from nude mice,and immunohistochemistry and western blot were used to detect the effect of PTD4-apoptin protein and the combination of PTD4-apoptin protein and autophagy inducer on autophagy in various gastric cancer tissues,as well as the changes in the expression of caspase-3 apoptotic protein.The experiment was repeated twice.Results:(1)In vivo experiments in nude mice showed that PTD4-apoptin protein had significant inhibitory effect on SGC7901 tumors of human gastric cancer with two different degrees of differentiation.Compared with P4 A group,the tumor inhibitory effect of P4A+Rap group was decreased.(2)Treated mice were euthanized at 15 days after the tumor tissue and divestitures immunohistochemistry and HE staining and immunohistochemical results show low differentiation immunohistochemical results trend of SGC7901 cells and induced to differentiate SGC7901 cells less differentiation trend is consistent,the result of the Rap alone,P4 A and combination of Rap group LC3 Ⅱexpression quantity is significantly higher than the control group(P<0.01,**),P62 expression were less than the control group(P<0.01,**);The expression level of c-caspase3 in P4 A protein alone group and P4 A combined with Rap group was significantly higher than that in PBS group and Rap group(P<0.01,**),and the expression level of c-caspase3 in P4 A protein combined with Rap group was significantly lower than that in P4 A protein alone group(P<0.01,**).(3)Tumor tissue protein extracted and Western blot test,results show that the LC3 Ⅱ Rap amount of protein expression and P4 A + Rap group than the control group increased,P62 expression was reduced;The expression of c-caspase 3 in P4A+Rap group was lower than that in P4 A group.Conclusions:(1)PTD4-apoptin significantly inhibited the growth of medium-and low-differentiated SGC7901 gastric cancer cell xenograft in nude mice.(2)Compared with the experimental group of moderately differentiated SGC7901 transplanted tumor,PTD4-apoptin has more obvious tumor inhibition effect on the experimental group of poorly differentiated SGC7901 transplanted tumor.(3)Compared with PTD4-apoptin alone groups,the antitumor effect of SGC7901 cell tumor transplantation was decreased,indicating that inducing autophagy in gastric cancer cells reduced the antitumor effect of PTD4-apoptin protein in vivo.