Proton pump inhibitors (PPIs) impact on tumour cell survival, metastatic potential and chemotherapy resistance, and affect expression of resistance-relevant miRNAs in esophageal cancer

Background: Neoadjuvant treatment plays a crucial role in the therapy of advanced esophageal cancer. However, response to radiochemotherapy varies widely. Proton pump inhibitors (PPIs) have been demonstrated to impact on chemotherapy in a variety of other cancers. We analyzed the impact of PPI treatment on esophageal cancer cell lines, and investigated mechanisms that mediate the effect of PPI treatment in this tumour. Methods. We investigated the effect of esomeprazole treatment on cancer cell survival, adhesion, migration and chemotherapy in human adeno-(OE19) and squamous-cell-carcinoma (KYSE410) cell lines. Furthermore, we investigated the effect of PPI treatment on intra-/extracellular pH and on expression of resistance-relevant miRNAs. Results: Esomeprazole significantly inhibited tumour cell survival (in a dose-dependent manner), adhesion and migration in both tumour subtypes. Furthermore, esomeprazole augmented the cytotoxic effect of cisplatin and 5-FU in both tumour subtypes. Surprisingly, PPI treatment led to a significant increase of intracellular pH and a decrease of the extracellular pH. Finally, we found esomeprazole affected expression of resistance-relevant miRNAs. Specifically, miR-141 and miR-200b were upregulated, whereas miR-376a was downregulated after PPI treatment in both tumour types. Conclusion: Our study demonstrates for the first time that PPIs impact on tumour cell survival, metastatic potential and sensitivity towards chemotherapy in esophageal cancer cell lines. Furthermore, we observed that in this tumour entity, PPIs do not lead to intracellular acidification, but affect the expression of resistance-relevant miRNAs.