Pantoprazole, an FDA-approved proton-pump inhibitor, suppresses colorectal cancer growth by targeting T-cell-originated protein kinase

The T-LAK Cell-originated Protein Kinase Signal Pathway Promotes Colorectal Cancer Metastasis

Approximately 90% of all cancer deaths arise from the metastatic dissemination of primary tumors. Metastasis is the most lethal attribute of colorectal cancer. New data regarding the molecules contributing to the metastatic phenotype, the pathways they control and the genes they regulate are very important for understanding the processes of metastasis prognosis and prevention in the clinic. The purpose of this study was to investigate the role of T-LAK cell-originated protein kinase (TOPK) in the promotion of colorectal cancer metastasis. TOPK is highly expressed in human metastatic colorectal cancer tissue compared with malignant adenocarcinoma. We identified p53-related protein kinase (PRPK) as a new substrate of TOPK. TOPK binds with and phosphorylates PRPK at Ser250 in vitro and ex vivo. This site plays a critical role in the function of PRPK. Cell lines stably expressing mutant PRPK (S250A), knockdown TOPK, knockdown PRPK or knockdown of both TOPK and PRPK significantly inhibited liver metastasis of human HCT116 colon cancer cells in a xenograft mouse model. Therefore, we conclude that TOPK directly promotes metastasis of colorectal cancer by modulating PRPK. Thus, these findings may assist in the prediction of prognosis or development of new therapeutic strategies against colon cancer.

Pantoprazole Induces Apoptosis of Leukemic Cells by Inhibiting Expression of P-Glycoprotein/Multidrug Resistance-Associated Protein-1 Through PI3K/AKT/mTOR Signaling

This study aims to investigate the effects and mechanism of pantoprazole on multidrug resistant leukemia K562/A02 and K562/ADM cell lines. K562/A02 and K562/ADM cells at logarithmic growth phase were pre-treated with different concentration of pantoprazole (0, 50, 100, 200 μg/mL) for 24 h. Flow cytometry was used to measure the cell growth cycle and apoptosis. RT-PCR and Western blot were used to measure the expression of p-PI3K, p-AKT, p-mTOR, P-glycoprotein (P-gp) and multidrug resistance-associated protein-1 (MRP1). Pantoprazole pretreatment significantly increased the ratio of G0/G1 phase but decreased the S phase of K562/A02 and K562/ADM cells in dose-dependent manner (p < 0.05). Flow cytometry analysis indicated that pretreatment of leukemic cells with pantoprazole induced apoptosis in a dose-dependent manner. RT-PCR and Western blot analysis indicated that pantoprazole pretreatment inhibited the mRNA and protein expression of p-PI3K, p-Akt, p-mTOR, P-gp and MRP1 in K562/A02 and K562/ADM cells in a dose-dependent manner (p < 0.05). Pantoprazole arrested cell cycle and induced apoptosis of multidrug resistant leukemic cells by inhibiting the expression of P-gp and MRP1 through PI3K/Akt/mTOR signaling pathway.

Proton pump inhibition and cancer therapeutics: A specific tumor targeting or it is a phenomenon secondary to a systemic buffering?

One of the unsolved mysteries in oncology includes the strategies that cancer cells adopt to cope with an adverse microenvironment. However, we knew, from the Warburg's discovery that through their metabolism based on sugar fermentation, cancer cells acidify their microenvironment and this progressive acidification induces a selective pressure, leading to the development of very malignant cells entirely armed to survive in the hostile microenvironment generated by their own metabolism. In the last decades a primordial role for proton exchangers has been supported as a key tumor advantage in facing off the acidic milieu. Proton exchangers do not allow intracellular acidification through a continuous elimination of H+ either outside the cells or within the internal vacuoles. This article wants to comment a translational process through that led to the preclinical demonstration that a class of proton pump inhibitors (PPI) exploited worldwide for peptic ulcer treatment and gastroprotection are indeed powerful chemosensitizers as well. In this process we achieved the clinical proof of concept that PPI may well be included in new anti-cancer strategies with a solid background and rationale.