title: Concurrent MEK and autophagy inhibition is required to restore cell death associated danger-signalling in Vemurafenib-resistant melanoma cells.
abstract: Vemurafenib (PLX4032), an inhibitor of BRAF(V600E), has demonstrated significant clinical anti-melanoma effects. However, the majority of treated patients develop resistance, due to a variety of molecular mechanisms including MAPK reactivation through MEK. The induction of a cancer cell death modality associated with danger-signalling resulting in surface mobilization of crucial damage-associated-molecular-patterns (DAMPs), e.g. calreticulin (CRT) and heat shock protein-90 (HSP90), from dying cells, is emerging to be crucial for therapeutic success. Both cell death and danger-signalling are modulated by autophagy, a key adaptation mechanism stimulated during melanoma progression. However, whether melanoma cell death induced by MAPK inhibition is associated with danger-signalling, and the reliance of these mechanisms on autophagy, has not yet been scrutinized. Using a panel of isogenic PLX4032-sensitive and resistant melanoma cell lines we show that PLX4032-induced caspase-dependent cell death and DAMPs exposure in the drug-sensitive cells, but failed to do so in the drug-resistant cells, displaying heightened MEK activation. MEK inhibitor, U0126, treatment sensitized PLX4032-resistant cells to death and re-established their danger-signalling capacity. Only melanoma cells exposing death-induced danger-signals were phagocytosed and induced DC maturation. Although the PLX4032-resistant melanoma cells displayed higher basal and drug-induced autophagy, compromising autophagy, pharmacologically or by ATG5 knockdown, was insufficient to re-establish their PLX4032 sensitivity. Interestingly, autophagy abrogation was particularly efficacious in boosting cell death and ecto-CRT/ecto-HSP90 in PLX4032-resistant cells upon blockage of MEK hyper-activation by U0126. Thus combination of MEK inhibitors with autophagy blockers may represent a novel treatment regime to increase both cell death and danger-signalling in Vemurafenib-resistant metastatic melanoma.
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Martin
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
authors.forename: A M
authors.initials: AM
authors.lastname: Dudek-Perić
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Maes
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
authors.forename: A D
authors.initials: AD
authors.lastname: Garg
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Gabrysiak
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Demirsoy
authors.affiliation: Laboratory of Lipid Metabolism and Cancer, Department of Oncology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 818, 3000 Leuven, Belgium.
authors.forename: J V
authors.initials: JV
authors.lastname: Swinnen
authors.affiliation: Cell Death Research and Therapy Unit, Department for Cellular and Molecular Medicine, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N1, Herestraat 49, Box 802, 3000 Leuven, Belgium. Electronic address: patrizia.agostinis@med.kuleuven.be.
authors.forename: P
authors.initials: P
authors.lastname: Agostinis
mesh_terms: D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D002070:Butadienes / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D018920:Coculture Techniques; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology* / Q000627:therapeutic use; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology* / Q000627:therapeutic use; D000077484:Vemurafenib
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D007211:Indoles; D009570:Nitriles; D013449:Sulfonamides; C113580:U 0126; D000077484:Vemurafenib; D020930:MAP Kinase Kinase Kinases
keywords: Autophagy; Cell death; Danger-signalling; Melanoma; PLX4032