Carcinogenesis Advance Access originally published online on November 28, 2007
Carcinogenesis 2008 29(2):381-389; doi:10.1093/carcin/bgm271
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Resveratrol-induced apoptosis depends on the lipid kinase activity of Vps34 and on the formation of autophagolysosomes
Laboratorio di Patologia Molecolare, Dipartimento di Scienze Mediche, Università del Piemonte Orientale ‘A. Avogadro’, Via Solaroli 17, 28100 Novara, Italy
* To whom correspondence should be addressed. Tel: +39 321 660607; Fax: +39 321620421; Email: isidoro{at}med.unipmn.it
In human colorectal DLD1 cancer cells, the dietary bioflavonoid resveratrol (RV) rapidly induced autophagy. This effect was reversible (on removal of the drug) and was associated with increased expression and cytosolic redistribution of the proteins Beclin1 and LC3 II. Supplementing the cells with asparagine (Asn) abrogated the Beclin-dependent autophagy. When applied acutely (2 h), RV was not toxic; however, reiterate chronic (48 h) exposure to RV eventually led to annexin V- and terminal deoxinucleotidyl transferase-mediated dUTP-biotin nick end labeling-positive cell death. This toxic effect was autophagy dependent, as it was prevented either by Asn, by expressing a dominant-negative lipid kinase-deficient class III phosphoinositide 3-phosphate kinase, or by RNA interference knockdown of Beclin1. Lamp2b silencing abolished the fusion of autophagosomes with lysosomes and preserved cell viability despite the ongoing formation of autophagosomes in cells chronically exposed to RV. The pan-caspase inhibitor benzyloxycarbonyl-Val–Ala–Asp-fluoromethylketone inhibited RV-induced cell death, but not autophagy. These results uncover a novel pathway of RV cytotoxicity in which autophagy plays a dual role: (i) at first, it acts as a prosurvival stress response and (ii) at a later time, it switches to a caspase-dependent apoptosis pathway. The present data also indicate that genetic or epigenetic inactivation of autophagy proteins in cancer cells may confer resistance to RV-mediated killing.
Abbreviations: Asn, asparagine; GFP, green fluorescent protein; MDC, monodansylcadaverine; PBS, phosphate-buffered saline; PI3K, phosphoinositide 3-phosphate kinase; RV, resveratrol; siRNA, small interference RNA; TUNEL, terminal deoxinucleotidyl transferase-mediated dUTP-biotin nick end labeling; ZVAD-fmk, benzyloxycarbonyl-Val–Ala–Asp-fluoromethylketone
Received July 26, 2007; revised November 20, 2007; accepted November 21, 2007.