title: Sorafenib-induced defective autophagy promotes cell death by necroptosis.
abstract: Autophagy is one of the main cytoprotective mechanisms that cancer cells deploy to withstand the cytotoxic stress and survive the lethal damage induced by anti-cancer drugs. However, under specific conditions, autophagy may, directly or indirectly, induce cell death. In our study, treatment of the Atg5-deficient DU145 prostate cancer cells, with the multi-tyrosine kinase inhibitor, sorafenib, induces mitochondrial damage, autophagy and cell death. Molecular inhibition of autophagy by silencing ULK1 and Beclin1 rescues DU145 cells from cell death indicating that, in this setting, autophagy promotes cell death. Re-expression of Atg5 restores the lipidation of LC3 and rescues DU145 and MEF atg5-/- cells from sorafenib-induced cell death. Despite the lack of Atg5 expression and LC3 lipidation, DU145 cells form autophagosomes as demonstrated by transmission and immuno-electron microscopy, and the formation of LC3 positive foci. However, the lack of cellular content in the autophagosomes, the accumulation of long-lived proteins, the presence of GFP-RFP-LC3 positive foci and the accumulated p62 protein levels indicate that these autophagosomes may not be fully functional. DU145 cells treated with sorafenib undergo a caspase-independent cell death that is inhibited by the RIPK1 inhibitor, necrostatin-1. Furthermore, treatment with sorafenib induces the interaction of RIPK1 with p62, as demonstrated by immunoprecipitation and a proximity ligation assay. Silencing of p62 decreases the RIPK1 protein levels and renders necrostatin-1 ineffective in blocking sorafenib-induced cell death. In summary, the formation of Atg5-deficient autophagosomes in response to sorafenib promotes the interaction of p62 with RIPK leading to cell death by necroptosis.
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Pedram
authors.initials: P
authors.lastname: Kharaziha
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Chioureas
authors.affiliation: Department of Medicine, School of Health Sciences, University of Athens, Athens, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Baltatzis
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Pedro
authors.initials: P
authors.lastname: Fonseca
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Patricia
authors.initials: P
authors.lastname: Rodriguez
authors.affiliation: Institute of Environmental Medicine, Division of Toxicology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Gogvadze
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Lennartsson
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Björklund
authors.affiliation: Institute of Environmental Medicine, Division of Toxicology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Boris
authors.initials: B
authors.lastname: Zhivotovsky
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Dan
authors.initials: D
authors.lastname: Grandér
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Egevad
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Sten
authors.initials: S
authors.lastname: Nilsson
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Theocharis
authors.initials: T
authors.lastname: Panaretakis
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D015153:Blotting, Western; D002478:Cells, Cultured; D019008:Drug Resistance, Neoplasm; D004622:Embryo, Mammalian / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000378:metabolism / Q000502:physiology; D009336:Necrosis; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D010588:Phagosomes / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D016601:RNA-Binding Proteins / Q000378:metabolism; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000378:metabolism; D000077157:Sorafenib; D046888:Tissue Array Analysis
chemical_list: C502778:ATG5 protein, human; D000970:Antineoplastic Agents; C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D008869:Microtubule-Associated Proteins; C118585:P62 protein, human; D010671:Phenylurea Compounds; D016601:RNA-Binding Proteins; D009536:Niacinamide; D000077157:Sorafenib; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases
keywords: Atg5; autophagy; necroptosis; prostate cancer; tyrosine kinase inhibitor