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Glycolytic pyruvate regulates P‐Glycoprotein expression in multicellular tumor spheroids via modulation of the intracellular redox state
Authors:Maria Wartenberg  Madeleine Richter  André Datchev  Sebastian Günther  Nada Milosevic  Mohamed M Bekhite  Hans‐Reiner Figulla  Josep M Aran  Jordi Pétriz  Heinrich Sauer
Institution:1. Department of Internal Medicine I, Cardiology Division, Friedrich Schiller University, Jena, Germany;2. Institute of Microbiology and Epizootics, Veterinary Faculty, Free University, Berlin, Germany;3. Department of Physiology, Justus Liebig University, Giessen, Germany;4. Medical and Molecular Genetics Center, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Hospital Duran i Reynals, L'Hospitalet de Llobregat, Barcelona, Spain;5. Institut de Recerca, Hospital Universitari, Vall d'Hebron, Barcelona, Spain
Abstract:ABC transporters like P‐glycoprotein (P‐gp/ABCB1) are membrane proteins responsible for the transport of toxic compounds out of non‐malignant cells and tumor tissue. Aim: To investigate the effect of glycolysis and the tissue redox state on P‐gp expression in multicellular tumor spheroids derived from prostate adenocarcinoma cells (DU‐145), glioma cells (Gli36), and the human cervix carcinoma cell line KB‐3‐1 transfected with a P‐gp–EGFP fusion gene that allows monitoring of P‐gp expression in living cells. During cell culture of DU‐145, Gli36, and KB‐3‐1 tumor spheroids P‐gp expression was observed as well as increased lactate and decreased pyruvate levels and expression of glycolytic enzymes. Inhibition of glycolysis for 24 h by either iodoacetate (IA) or 2‐deoxy‐D ‐glucose (2‐DDG) downregulated P‐gp expression which was reversed upon coincubation with the radical scavenger ebselen as shown by semi‐quantitative immunohistochemisty in DU‐145 and Gli36 tumor spheroids, and by EGFP fluorescence in KB‐3‐1 tumor spheroids. Consequently endogenous ROS generation in DU‐145 tumor spheroids was increased in the presence of either IA or 2‐DDG, which was abolished upon coincubation with ebselen. Exogenous addition of pyruvate significantly reduced ROS generation, increased P‐gp expression as well as efflux of the P‐gp substrate doxorubicin. Doxorubicin transport was significantly blunted by 2‐DDG and IA, indicating that inhibition of glycolysis reversed the multidrug resistance phenotype. In summary our data demonstrate that P‐gp expression in tumor spheroids is closely related to the glycolytic metabolism of tumor cells and can be downregulated by glycolysis inhibitors via mechanisms that involve changes in the cellular redox state. J. Cell. Biochem. 109: 434–446, 2010. © 2009 Wiley‐Liss, Inc.
Keywords:glycolysis  multidrug resistance  P‐glycoprotein  reactive oxygen species
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