In vivo pH in metabolic-defective Ras-transformed fibroblast tumors: Key role of the monocarboxylate transporter, MCT4, for inducing an alkaline intracellular pH

Authors

  • Johanna Chiche,

    1. Institute of Developmental Biology and Cancer, CNRS UMR 6543, Centre Antoine Lacassagne, Université de Nice, France
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  • Yann Le Fur,

    1. Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Faculté de Médecine de la Timone, Université Aix-Marseille, Marseille, France
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  • Christophe Vilmen,

    1. Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Faculté de Médecine de la Timone, Université Aix-Marseille, Marseille, France
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  • Frédéric Frassineti,

    1. INSERM UMR U911, Université de la Méditerranée, Marseille, France
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  • Laurent Daniel,

    1. INSERM UMR U911, Université de la Méditerranée, Marseille, France
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  • Andrew P. Halestrap,

    1. School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol, United Kingdom
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  • Patrick J. Cozzone,

    1. Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Faculté de Médecine de la Timone, Université Aix-Marseille, Marseille, France
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  • Jacques Pouysségur,

    1. Institute of Developmental Biology and Cancer, CNRS UMR 6543, Centre Antoine Lacassagne, Université de Nice, France
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  • Norbert W. Lutz

    Corresponding author
    1. Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Faculté de Médecine de la Timone, Université Aix-Marseille, Marseille, France
    • CRMBM, UMR 6612 CNRS, Faculté de Médecine, Université de la Méditerranée, 27 bd Jean Moulin, F-13005 Marseille, France
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    • Tel: +33-491-32-4814, Fax: +33-491-25-6539


Abstract

We present an investigation of tumor pH regulation, designed to support a new anticancer therapy concept that we had previously proposed. Our study uses a tumor model of ras-transformed hamster fibroblasts, CCL39, xenografted in the thighs of nude mice. We demonstrate, for the first time, that genetic modifications of specific mechanisms of proton production and/or proton transport result in distinct, reproducible changes in intracellular and extracellular tumor pH that can be detected and quantified noninvasively in vivo, simultaneously with determinations of tumor energetic status and necrosis in the same experiment. The CCL39 variants used were deficient in the sodium/proton exchanger, NHE-1, and/or in the monocarboxylate transporter, MCT4; further, variants were deficient in glycolysis or respiration. MCT4 expression markedly increased the gradient between intracellular and extracellular pH from 0.14 to 0.43 when compared to CCL39 wild-type tumors not expressing MCT4. The other genetic modifications studied produced smaller but significant increases in intracellular and decreases in extracellular pH. In general, increased pH gradients were paralleled by increased tumor growth performance and diminished necrotic regions, and 50% of the CCL39 variant expressing neither MCT4 nor NHE-1, but possessing full genetic capacity for glycolysis and oxidative phosphorylation, underwent regression before reaching a 1-cm diameter. Except for CCL39 wild-type tumors, no significant HIF-1α expression was detected. Our in vivo results support a multipronged approach to tumor treatment based on minimizing intracellular pH by targeting several proton production and proton transport processes, among which the very efficient MCT4 proton/lactate co-transport deserves particular attention.

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