OncoTargets and Therapy (Oct 2018)
Effects of proton pump inhibitors on reversing multidrug resistance via downregulating V-ATPases/PI3K/Akt/mTOR/HIF-1α signaling pathway through TSC1/2 complex and Rheb in human gastric adenocarcinoma cells in vitro and in vivo
Abstract
Min Chen,1,* Jian Lu,1–3,* Wei Wei,4,* Ying Lv,1 Xiaoqi Zhang,1 Yuling Yao,1 Lei Wang,1 Tingsheng Ling,1,5 Xiaoping Zou1 1Department of Gastroenterology the Affiliated Drum Tower Hospital of Nanjing University, Medical School, Nanjing 210008, People’s Republic of China; 2Department of Gastroenterology, the Affiliated Drum Tower Clinical Medical School of Nanjing Medical University, Nanjing 210008, People’s Republic of China; 3Department of Gastroenterology, the affiliated Wuxi Second Hospital of Nanjing Medical University, Wuxi 214002, People’s Republic of China; 4Department of Gastrointestinal Surgery, the Second Affiliated Hospital of Nanjing Medical University, Nanjing 210011, People’s Republic of China; 5Department of Gastroenterology, Nanjing Gaochun People’s Hospital, Nanjing 211300, People’s Republic of China *These authors contributed equally to this work Background: Our study aimed to explore the effects of PPIs on reversing multidrug resistance (MDR) to chemotherapy in gastric cancer by inhibiting the expression of V-ATPases and the PI3K/Akt/mTOR/ HIF-1α signal pathway. Methods: The gastric cancer cell lines SGC7901 and the multidrug resistance cell lines SGC7901/MDR were pretreated by the pantoprazole or the esomeprazole, respectively. Real-time PCR was used to determine mRNA levels, and western blotting and immunofluorescent staining analyses were employed to determine the protein expressions and intracellular distributions of the V-ATPases, PI3K, Akt, mTOR, HIF-1α, P-gp and MRP1 before and after PPIs pretreatment. SGC7901/MDR cells were planted on the athymic nude mice. Then the effects of PPZ pretreatment and/or ADR were compared by determining the tumor size, tumor weight and nude mice weight. Results: PPIs pretreatment could inhibit mRNA levels of V-ATPases, MDR1 and MRP1, PI3K, Akt, mTOR and HIF-1α. PPIs inhibited V-ATPases and down-regulated the expressions of P- gp and MRP1. And further to block the expression of mTOR by Rapamycin could obviously inhibit the expressions of HIF-1α, P-gp and MRP1 in a dose-dependent manner. Therefore, PPIs inhibited the expressions of V-ATPases and then reversed MDR of the chemotherapy in gastric cancer by inhibiting P-gp and MRP1, and it could be speculated that the mechanism might be closely related to down-regulating the PI3K/Akt/mTOR/HIF-1α signaling pathway. Meanwhile, PPIs also could inhibit the expressions of TSC1/TSC2 complex and Rheb which might be involved into regulating the signaling pathway intermediately. The weight growth rate of the mice bearing tumor in the treatment group was lower than that of the nude mice in the normal group, while the weight growth rate of the mice in control group was significantly lower than that of the normal group and the treatment group, presenting a downward trend. Conclusion: Therefore, PPIs inhibited the expressions of V-ATPases and then reversed MDR of the chemotherapy in gastric cancer by inhibiting P-gp and MRP1, and it could be speculated that the mechanism might be closely related to down-regulating the PI3K/Akt/mTOR/HIF-1α signaling pathway, and also to inhibiting the expressions of TSC1/TSC2 complex and Rheb which might be involved into regulating the signaling pathway intermediately. Keywords: gastric adenocarcinoma, V-ATPases, tumor acidity, hypoxia, proton pump inhibitors, multidrug resistance, signaling pathway
