title: Vaccinia virus induces programmed necrosis in ovarian cancer cells.
abstract: The mechanisms by which oncolytic vaccinia virus induces tumor cell death are poorly understood. We have evaluated cell death pathways following infection of ovarian cancer cells with both wild-type and thymidine kinase-deleted (dTK) Lister strain vaccinia. We show that death does not rely upon classical apoptosis despite the appearances of some limited apoptotic features, including phosphatidylserine externalization and appearance of sub-G1 DNA populations. Vaccinia infection induces marked lipidation of LC3 proteins, but there is no general activation of the autophagic process and cell death does not rely upon autophagy induction. We show that vaccinia induces necrotic morphology on transmission electron microscopy, accompanied by marked by reductions in intracellular adenosine triphosphate, altered mitochondrial metabolism, and release of high mobility group box 1 (HMGB1) protein. This necrotic cell death appears regulated, as infection induces formation of a receptor interacting protein (RIP1)/caspase-8 complex. In addition, pharmacological inhibition of both RIP1 and substrates downstream of RIP1, including MLKL, significantly attenuate cell death. Blockade of TNF-α, however, does not alter virus efficacy, suggesting that necrosis does not result from autocrine cytokine release. Overall, these results show that, in ovarian cancer cells, vaccinia virus causes necrotic cell death that is mediated through a programmed series of events.
authors.affiliation: Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, London, UK.
authors.forename: Lynsey M
authors.initials: LM
authors.lastname: Whilding
authors.forename: Kyra M
authors.initials: KM
authors.lastname: Archibald
authors.forename: Hagen
authors.initials: H
authors.lastname: Kulbe
authors.forename: Frances R
authors.initials: FR
authors.lastname: Balkwill
authors.forename: Daniel
authors.initials: D
authors.lastname: Öberg
authors.forename: Iain A
authors.initials: IA
authors.lastname: McNeish
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D046529:Microscopy, Electron, Transmission; D009336:Necrosis; D009374:Neoplasms, Experimental; D050130:Oncolytic Virotherapy / Q000379:methods*; D050504:Oncolytic Viruses / Q000235:genetics / Q000502:physiology; D010051:Ovarian Neoplasms / Q000473:pathology*; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D048069:Tumor Necrosis Factors / Q000378:metabolism; D014616:Vaccinia virus / Q000235:genetics / Q000502:physiology*
chemical_list: D007093:Imidazoles; D007211:Indoles; D048069:Tumor Necrosis Factors; C507699:necrostatin-1; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D053181:Caspase 8