MCL-1 dependency of cisplatin-resistant cancer cells Judith Michels a,b,c , Florine Obrist a,b,c,d , Ilio Vitale f , Delphine Lissa a,b,c , Pauline Garcia a,b,c , Parviz Behnam-Motlagh e , Kimitoshi Kohno f , Gen Sheng Wu g , Catherine Brenner h , Maria Castedo a,b,c,1, *, Guido Kroemer a,b,c,i,j,1, * a Equipe 11 labellise ´e par la Ligue Nationale contre le Cancer, Centre de Recherche des Cordeliers, INSERM U1138, F-75006 Paris, France b Universite ´ Paris Descartes, Sorbonne Paris Cite ´, F-75005 Paris, France c Metabolomics and Cell Biology Platforms, Gustave Roussy, F-94805 Villejuif, France d Universite ´ Paris Sud, F-94805 Villejuif, France e Regina Elena National Cancer Institute, 00144 Rome, Italy f Department of Medical Biosciences, Clinical Chemistry, Umea ˚ University, Umea ˚ SE-90187, Sweden g Department of Molecular Biology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan h Molecular Therapeutics Program, Karmanos Cancer Institute, Department of Oncology and Pathology, Wayne State University School of Medicine, Detroit, MI 48201, USA i U769, INSERM-LabEx LERMIT, Universite ´ Paris-Sud, Faculte ´ de Pharmacie, Chaˆtenay Malabry F-92296, France j Poˆle de Biologie, Ho ˆpital Europe ´en Georges Pompidou, AP-HP, F-75015 Paris, France 1. Introduction Cis-diamminedichloroplatinum(II) (CDDP), which is best known as cisplatin, is a widely used chemotherapeutic agent for the treatment of lung cancers, head and neck cancers, ovarian carcinoma, as well as other types of malignancy [1–3]. Although therapy with CDDP often leads to a reduction in tumor growth or volume, relapse is a close-to-invariant phenomenon, with the notable exception of testicular cancers that often are cured by CDDP-based chemotherapeutic regimens [4–6]. Hence, CDDP resistance constitutes a major medical issue that awaits urgent mechanistic elucidation and therapeutic countermeasures. In mechanistic terms, CDDP resistance may occur at several levels. Pre-target resistance mechanisms interfere with the steps preceding the binding of cisplatin to DNA and hence affect the transport of CDDP from the plasma to the nucleus. On-target resistance directly relate to DNA-CDDP adducts. Post-target Biochemical Pharmacology xxx (2014) xxx–xxx * Corresponding authors. E-mail addresses: Marie.CASTEDO-DELRIEU@gustaveroussy.fr (M. Castedo), kroemer@orange.fr (G. Kroemer). 1 These authors share senior co-authorship. A R T I C L E I N F O Article history: Received 11 June 2014 Received in revised form 25 July 2014 Accepted 28 July 2014 Available online xxx Keywords: MCL-1 Chemoresistance Obatoclax PARP1 Apoptosis A B S T R A C T The selection of human cancer cell lines in cis-diamminedichloroplatinum(II) (CDDP, best known as cisplatin) is accompanied by stereotyped alterations that contribute to the acquisition of a CDDP- resistant state. Thus, CDDP resistance often leads to the upregulation of the DNA repair enzyme poly (ADP-ribose) polymerase-1 (PARP1) with the consequent intracellular accumulation of poly (ADP- ribose) (PAR)-modified proteins. Here we report another frequent alteration accompanying CDDP resistance, namely upregulation of the antiapoptotic BCL-2 family protein MCL-1. Six out of 8 CDDP resistant cancer cell lines manifested an increase in MCL-1 protein expression level, while only a minority of cell lines overexpressed BCL-2 or BCL- X L. BCL- X L was decreased in six out of 8 cancer cell lines. Importantly, MCL-1 overexpressing, CDDP resistant cells appear to be ‘addicted’ to MCL-1 because they died upon depletion of MCL-1 by RNA interference or pharmacological inhibition of MCL-1 expression by the BH3 mimetic obatoclax. Knockdown of PARP1 did not succeed in reducing MCL-1 expression, while depletion or inhibition of MCL-1 failed to affect the activity of PARP1. Hence, the two resistance mechanisms are not linked to each other by a direct cause-effect relationship. Importantly, CDDP-resistant, MCL-1 overexpressing human non-small cell lung cancers responded to monotherapy with obatoclax in vivo, in xenotransplanted mice, underscoring the probable therapeutic relevance of these findings. ß 2014 Published by Elsevier Inc. G Model BCP-12045; No. of Pages 7 Please cite this article in press as: Michels J, et al. MCL-1 dependency of cisplatin-resistant cancer cells. Biochem Pharmacol (2014), http://dx.doi.org/10.1016/j.bcp.2014.07.029 Contents lists available at ScienceDirect Biochemical Pharmacology jo u rn al h om epag e: ww w.els evier.c o m/lo cat e/bio c hem p har m http://dx.doi.org/10.1016/j.bcp.2014.07.029 0006-2952/ß 2014 Published by Elsevier Inc.