• Open Access

Epigallocatechin-3-gallate induces mesothelioma cell death via H2O2−dependent T-type Ca2+ channel opening

Authors

  • Elia Ranzato,

    Corresponding author
    1. Dipartimento di Scienze e Innovazione Tecnologica, DiSIT, University of Piemonte Orientale “Amedeo Avogadro”, Alessandria, Italy
    • Correspondence to: Elia RANZATO, DiSIT, University of Piemonte Orientale “Amedeo Avogadro”, viale T. Michel 11, 15121 Alessandria, Italy.

      Tel.: +39-0131-360260

      Fax: +39-0131-360243

      E-mail: ranzato@mfn.unipmn.it

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    • These two authors contributed equally to this work.
  • Simona Martinotti,

    1. Dipartimento di Scienze e Innovazione Tecnologica, DiSIT, University of Piemonte Orientale “Amedeo Avogadro”, Alessandria, Italy
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    • These two authors contributed equally to this work.
  • Valeria Magnelli,

    1. Dipartimento di Scienze e Innovazione Tecnologica, DiSIT, University of Piemonte Orientale “Amedeo Avogadro”, Alessandria, Italy
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  • Bruno Murer,

    1. Department of Anatomic Pathology, Dell'Angelo Hospital, Zelarino, Italy
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  • Stefano Biffo,

    1. Dipartimento di Scienze e Innovazione Tecnologica, DiSIT, University of Piemonte Orientale “Amedeo Avogadro”, Alessandria, Italy
    2. Molecular Histology and Cell Growth Laboratory, San Raffaele Science Institute, Milan, Italy
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  • Luciano Mutti,

    1. Dept General Medicine, Lab of Clinical Oncology, Vercelli National Health Trust, Vercelli, Italy
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  • Bruno Burlando

    1. Dipartimento di Scienze e Innovazione Tecnologica, DiSIT, University of Piemonte Orientale “Amedeo Avogadro”, Alessandria, Italy
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Abstract

Malignant mesothelioma (MMe) is a highly aggressive, lethal tumour requiring the development of more effective therapies. The green tea polyphenol epigallocathechin-3-gallate (EGCG) inhibits the growth of many types of cancer cells. We found that EGCG is selectively cytotoxic to MMe cells with respect to normal mesothelial cells. MMe cell viability was inhibited by predominant induction of apoptosis at lower doses and necrosis at higher doses. EGCG elicited H2O2 release in cell cultures, and exogenous catalase (CAT) abrogated EGCG-induced cytotoxicity, apoptosis and necrosis. Confocal imaging of fluo 3-loaded, EGCG-exposed MMe cells showed significant [Ca2+]i rise, prevented by CAT, dithiothreitol or the T-type Ca2+ channel blockers mibefradil and NiCl2. Cell loading with dihydrorhodamine 123 revealed EGCG-induced ROS production, prevented by CAT, mibefradil or the Ca2+ chelator BAPTA-AM. Direct exposure of cells to H2O2 produced similar effects on Ca2+ and ROS, and these effects were prevented by the same inhibitors. Sensitivity of REN cells to EGCG was correlated with higher expression of Cav3.2 T-type Ca2+ channels in these cells, compared to normal mesothelium. Also, Cav3.2 siRNA on MMe cells reduced in vitro EGCG cytotoxicity and abated apoptosis and necrosis. Intriguingly, Cav3.2 expression was observed in malignant pleural mesothelioma biopsies from patients, but not in normal pleura. In conclusion, data showed the expression of T-type Ca2+ channels in MMe tissue and their role in EGCG selective cytotoxicity to MMe cells, suggesting the possible use of these channels as a novel MMe pharmacological target.

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