Research On Improving Chemotherapy Sensitivity Of Cisplatin By Pantoprazole Through Inhibiting Autophagy In Gastric Cancer Cell Line SGC-7901and Its Mechanism

Background and aims:Human gastric adenocarcinoma is one of common malignant tumors in the digestive system, with a poor efficiency responsed to chemotherapy. Application of high efficiency and low toxic chemotherapy sensitizers can be one of the optimized solutions to improve the effects of chemotherapy and also to reduce the side effects. Proton pump inhibitors (PPIs) can inhibit vacuolar type ATPases, reverse internal and external pH gradient of the tumor cells and enhance biological utilization of chemotherapeutic agents to improve the sensitivity of chemotherapy. Rencent studies show that PPIs could inhibit autophagy, and thus our research is aimed to investigate whether pantoprazole (PPZ), one of the common PPIs, could improve the sensitivity of chemotherapy of gastric adenocarcinoma cell lines through inhibiting autophagy and its possible mechanism.Metholds:1) Ultrastructural changes were observed in SGC-7901cells after cisplatin (DDP) treatment through the electron microscope;2) The expression of p62was determined after24h treatment of DDP and PPZ in SGC-7901cell line using Western Blotting;3) The distribution and positioning of fluorescent-labeled LC3in cells was observed after24h treatment of DDP and PPZ through fluorescence microscope;4) the expression of ATG7and p62was observed after siRNA targeted ATG7;5) Influences on SGC-7901cell proliferation rate were detected using CCK-8after treatment of PPZ, PPZ pretreatment and siRNA interference expression of ATG7;6) apoptosis rates were detected united with membrane protein V-fluorescein isothiocyanate-propidium iodide (Annexin V-FITC-PI) apoptosis detection kit test;7) Wwstern Blotting were employed to test p62and mTOR protein expression of mentioned groups.Results:The treatment of1μg/ml cisplatin for24h could significantly induce autophagy in SGC-7901cell, and two-membrane structures packaged the contents of cytoplasm were observed in the living cells, and at the same time the expression of p62were significantly decreased, besides red spots of fluorescent-stained LC3inside the cell were significantly increased. The treatment of80μg/ml PPZ for24h could increase the expression of p62and also the red spots of fluorescent-stained LC3, inhibiting tumor cell autophagy, reducing cell proliferation rateand promoting cell apoptosis. Technology of siRNA targeted ATG7could inbibit ATG7expression, and the expression of p62was higher, which significantly suppressed autophagy in cells and decreased cancer cell survival rates against DDP. PPZ pretreatment could improve the chemotherapy sensitivity of the SGC-7901line to cisplatin and cell apoptosis (P<0.05), but there was no obvious difference between the groups of PPZ pretreatment and cisplatin treatment after siRNA interference. However, the former had slightly better effect of chemotherapy than the latter. The expression of mTOR in the group of PPZ treatment or PPZ pretreatment were significantly higher compared with its corresponding group without PPZ, which has statistically significance(P<0.05), and these results coincidented with the expression of p62.Conclusions:1μg/ml DDP can induce autophagy in SGC-7901cell lines, and after inhibition of autophagy through siRNA targeted ATG7, sensitivity of cisplatin chemotherapy to SGC-7901was increased.80μg/ml PPZ can inhibit autophagy, and PPZ pretreatment could improve sensitivity of cisplatin in the cancer cells, enhance the cell apoptosis rate. mTOR may mediate the mechanism of improving cancer cell death and chemotherapy sensitivityof cisplatin by pantoprazole.