title: Epigallocatechin-3-gallate induces mesothelioma cell death via H2 O2 -dependent T-type Ca2+ channel opening.
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 H(2) O(2)  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 [Ca(2+) ](i)  rise, prevented by CAT, dithiothreitol or the T-type Ca(2+)  channel blockers mibefradil and NiCl(2) . Cell loading with dihydrorhodamine 123 revealed EGCG-induced ROS production, prevented by CAT, mibefradil or the Ca(2+)  chelator BAPTA-AM. Direct exposure of cells to H(2) O(2)  produced similar effects on Ca(2+)  and ROS, and these effects were prevented by the same inhibitors. Sensitivity of REN cells to EGCG was correlated with higher expression of Ca(v) 3.2 T-type Ca(2+)  channels in these cells, compared to normal mesothelium. Also, Ca(v) 3.2 siRNA on MMe cells reduced in vitro EGCG cytotoxicity and abated apoptosis and necrosis. Intriguingly, Ca(v) 3.2 expression was observed in malignant pleural mesothelioma biopsies from patients, but not in normal pleura. In conclusion, data showed the expression of T-type Ca(2+)  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.
authors.affiliation: Dipartimento di Scienze e Innovazione Tecnologica, DiSIT, University of Piemonte Orientale "Amedeo Avogadro", Alessandria, Italy. ranzato@mfn.unipmn.it
authors.forename: Elia
authors.initials: E
authors.lastname: Ranzato
authors.forename: Simona
authors.initials: S
authors.lastname: Martinotti
authors.forename: Valeria
authors.initials: V
authors.lastname: Magnelli
authors.forename: Bruno
authors.initials: B
authors.lastname: Murer
authors.forename: Stefano
authors.initials: S
authors.lastname: Biffo
authors.forename: Luciano
authors.initials: L
authors.lastname: Mutti
authors.forename: Bruno
authors.initials: B
authors.lastname: Burlando
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008654:Mesothelioma / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D020748:Mibefradil / Q000494:pharmacology; D010994:Pleura / Q000166:cytology / Q000378:metabolism; D010997:Pleural Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type; D002614:Chelating Agents; D017382:Reactive Oxygen Species; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D020748:Mibefradil; D004533:Egtazic Acid; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate; D002374:Catalase; D002118:Calcium