Volume 123, Issue 11 pp. 2532-2542
Cancer Cell Biology

Acidosis induces multi-drug resistance in rat prostate cancer cells (AT1) in vitro and in vivo by increasing the activity of the p-glycoprotein via activation of p38

Christoph Sauvant

Christoph Sauvant

Physiologisches Institut, Universität Würzburg, Würzburg, Germany

C. Sauvant and M. Nowak contributed equally to this work and are both to be considered as first authors.

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Martin Nowak

Martin Nowak

Institut für Physiologie und Pathophysiologie, Universität Mainz, Mainz, Germany

C. Sauvant and M. Nowak contributed equally to this work and are both to be considered as first authors.

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Claudia Wirth

Claudia Wirth

Physiologisches Institut, Universität Würzburg, Würzburg, Germany

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Bettina Schneider

Bettina Schneider

Julius-Bernstein-Institut für Physiologie, Universität Halle-Wittenberg, Halle, Germany

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Anne Riemann

Anne Riemann

Julius-Bernstein-Institut für Physiologie, Universität Halle-Wittenberg, Halle, Germany

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Michael Gekle

Corresponding Author

Michael Gekle

Julius-Bernstein-Institut für Physiologie, Universität Halle-Wittenberg, Halle, Germany

M. Gekle and O. Thews contributed equally to this work and are both to be considered as senior authors.

Fax: +49-345-557-4019.

Michael Gekle, Julius-Bernstein-Institut für Physiologie, Universität Halle-Wittenberg, Magdeburger Strasse 6, 06112 Halle (Saale), Germany

Oliver Thews, Institut für Physiologie und Pathophysiologie, Universität Mainz, Duesbergweg 6, 55099 Mainz, Germany

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Oliver Thews

Corresponding Author

Oliver Thews

Institut für Physiologie und Pathophysiologie, Universität Mainz, Mainz, Germany

M. Gekle and O. Thews contributed equally to this work and are both to be considered as senior authors.

Fax: +496-131-392-4543.

Michael Gekle, Julius-Bernstein-Institut für Physiologie, Universität Halle-Wittenberg, Magdeburger Strasse 6, 06112 Halle (Saale), Germany

Oliver Thews, Institut für Physiologie und Pathophysiologie, Universität Mainz, Duesbergweg 6, 55099 Mainz, Germany

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First published: 26 August 2008
Citations: 88

M. Gekle and O. Thews contributed equally to this work and are both to be considered as senior authors.

Fax: +49-345-557-4019.

Fax: +496-131-392-4543.

Abstract

Because solid growing tumors often show hypoxia and pronounced extracellular acidosis, the aim of this study was to analyze the impact of an acidotic environment on the activity of the p-glycoprotein (pGP) and on the cellular content and cytotoxicity of the chemotherapeutic drug daunorubicin in the AT1 R-3327 Dunning prostate carcinoma cell line cultured in vitro and in vivo. In vitro, extracellular acidosis (pH 6.6) activated p38 and ERK1/2 and thereby induced daunorubicin resistance via a pronounced activation of pGP. De-novo protein synthesis was not necessary and analysis of transport kinetics indicated a fast and persistent pGP activation at pH 6.6 (when compared with 7.4). Intracellular acidification also induced daunorubicin resistance via activation of pGP, which was mediated by activation of p38 alone. In vivo, tumors were implanted subcutaneously, and the tumor pH was artificially lowered by forcing anaerobic metabolism. In vivo, the reduced extracellular pH of 6.6 was also able to induce daunorubicin resistance, which was abolished by inhibition of p38. These results suggest that pGP activity is dependent on extracellular pH in vitro and in vivo. Moreover, there is strong indication that this effect is mediated via activation of p38 in vivo. Activation of ERK is also suitable to induce pGP activity. Therefore, inhibition of p38 (and ERK) may be used to prevent acidosis induced increase in pGP activity and thereby attenuate multidrug resistance. In addition, supportive treatments reducing tumor acidosis may improve the cytotoxic effect of chemotherapeutic drugs. © 2008 Wiley-Liss, Inc.

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