Targeting the multidrug transporter Patched potentiates chemotherapy efficiency on adrenocortical carcinoma in vitro and in vivo Anida Hasanovic 1,2,3,4 , Carmen Ruggiero 1,2,3,4‡ , Sara Jung 5‡ , Ida Rapa 6 , Laurie Signetti 1,2,3,4 , Monia Ben Hadj 1,2,3,4 , Massimo Terzolo 6 , Felix Beuschlein 5,7 , Marco Volante 6 , Constanze Hantel 5,7§ , Enzo Lalli 1,2,3,4§ and Isabelle Mus-Veteau 1,2,3,4 1 Universit eC^ ote d’Azur, Sophia Antipolis, Valbonne, France 2 CNRS UMR7275, Sophia Antipolis, Valbonne, France 3 NEOGENEX CNRS International Associated Laboratory, Sophia Antipolis, Valbonne, France 4 Institut de Pharmacologie Mol eculaire et Cellulaire, Sophia Antipolis, Valbonne, France 5 Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universit€ at, Munich, Germany 6 Department of Oncology, University of Turin at San Luigi Hospital, Orbassano, Turin, Italy 7 Klinik f€ ur Endokrinologie, Diabetologie und Klinische Ern€ ahrung, Universit€ atsspital Z€ urich, Zurich, Switzerland One of the crucial challenges in the clinical management of cancer is the resistance to chemotherapeutics. We recently dem- onstrated that the Hedgehog receptor Patched, which is overexpressed in many recurrent and metastatic cancers, is a multi- drug transporter for chemotherapeutic agents such as doxorubicin. The present work provides evidences that Patched is expressed in adrenocortical carcinoma (ACC) patients, and is a major player of the doxorubicin efflux and the doxorubicin resistance in the human ACC cell line H295R. We discovered that methiothepin inhibits the doxorubicin efflux activity of Patched. This drug-like molecule enhances the cytotoxic, pro-apoptotic, antiproliferative and anticlonogenic effects of doxoru- bicin on ACC cells which endogenously overexpress Patched, and thereby mitigates the resistance of these cancer cells to doxorubicin. Moreover, we report that in mice the combination of methiothepin with doxorubicin prevents the development of xenografted ACC tumors more efficiently than doxorubicin alone by enhancing the accumulation of doxorubicin specifically in tumors without obvious undesirable side effects. Our results suggest that the use of an inhibitor of Patched drug efflux such as methiothepin in combination with doxorubicin could be a promising therapeutic option for adrenocortical carcinoma, and most likely also for other Patched-expressing cancers. Introduction Despite the major progresses in biomedical research and the development of novel therapeutic strategies, cancer remains among the dominant causes of death worldwide. One of the crucial challenges in the clinical management of cancer is pri- mary (intrinsic) and secondary (acquired) resistance to both conventional and targeted chemotherapeutics. Multidrug resistance (MDR) has been intensively studied, and one of the most prominent mechanisms underlying MDR is overex- pression of members of the family of ATP-binding cassette (ABC) transporters. 1,2 These transporters use energy derived from the hydrolysis of ATP to transport a wide range of Key words: chemotherapy resistance, Patched, Hedgehog receptor, multidrug resistance, drug efflux pump, drug efflux inhibitor, cancers, adrenocortical carcinoma Additional Supporting Information may be found in the online version of this article. Conflict of interest: The authors declare no potential conflicts of interest. ‡ C.R. and S.J. contributed equally to this work § C.H. and E.L. contributed equally to this work Grant sponsor: Centre National de la Recherche Scientifique; Grant sponsor: Association France Cancer; Grant sponsor: Region Provence Alpes C^ ote d’Azur; Grant number: APRF program 2013-17362; Grant sponsor: Agence Nationale de la Recherche (ANR); Grant number: ANR-15-IDEX-01; Grant sponsor: French National Research Agency (ANR) through the «Investments for the Future » LABEX SIGNALIFE program; Grant number: ANR-11-LABX-0028-01; Grant sponsor: Fondation de France “Recherche fondamentale et clinique sur le cancer 2015”; Grant number: 00057927; Grant sponsor: The Wilhelm-Sander-Stiftung; Grant number: 2014.033.1 DOI: 10.1002/ijc.31296 History: Received 19 Oct 2017; Accepted 23 Jan 2018; Online 7 Feb 2018 Correspondence to: Isabelle Mus-Veteau, Institut de Pharmacologie Mol  eculaire et Cellulaire, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France, Tel.: 33-4-93-95-77-51, Fax: 33-4-93-95-77-08, E-mail: mus-veteau@ipmc.cnrs.fr Cancer Therapy and Prevention Int. J. Cancer: 143, 199–211 (2018) V C 2018 UICC International Journal of Cancer IJC