Oncolytic Group B Adenovirus Enadenotucirev Mediates Non-apoptotic Cell Death with Membrane Disruption and Release of Inflammatory Mediators

Abstract

Enadenotucirev (EnAd) is a chimeric group B adenovirus isolated by bioselection from a library of adenovirus serotypes. It replicates selectively in and kills a diverse range of carcinoma cells, shows effective anticancer activity in preclinical systems, and is currently undergoing phase I/II clinical trials. EnAd kills cells more quickly than type 5 adenovirus, and speed of cytotoxicity is dose dependent. The EnAd death pathway does not involve p53, is predominantly caspase independent, and appears to involve a rapid fall in cellular ATP. Infected cells show early loss of membrane integrity; increased exposure of calreticulin; extracellular release of ATP, HSP70, and HMGB1; and influx of calcium. The virus also causes an obvious single membrane blister reminiscent of ischemic cell death by oncosis. In human tumor biopsies maintained in ex vivo culture, EnAd mediated release of pro-inflammatory mediators such as TNF-α, IL-6, and HMGB1. In accordance with this, EnAd-infected tumor cells showed potent stimulation of dendritic cells and CD4+ T cells in a mixed tumor-leukocyte reaction in vitro. Whereas many viruses have evolved for efficient propagation with minimal inflammation, bioselection of EnAd for rapid killing has yielded a virus with a short life cycle that combines potent cytotoxicity with a proinflammatory mechanism of cell death.

External Beam Radiation Therapy and Enadenotucirev: Inhibition of the DDR and Mechanisms of Radiation-Mediated Virus Increase

“…Dyer at al. have provided evidence that EnAd induces an immunogenic cell death [5]; it may therefore provide a useful adjunct alongside this treatment modality. The primary cell line utilised in vitro in this study is A549, derived from a lung carcinoma and selected because of its relative radioresistance.…”

“…In contrast to other therapies, oncolytic virotherapy is unique in that the initial dose is amplified, potentially allowing for lower administered doses and therefore reduced off-target toxicity. In some cases, oncolytic viruses can also trigger the release of pro-inflammatory pathogen-associated molecular patterns or danger-associated molecular patterns [3][4][5]. A number of viruses, including adenoviruses, are currently being explored as oncolytic agents in the clinic [6,7].…”

Surviving Deadly Lung Infections: Innate Host Tolerance Mechanisms in the Pulmonary System

“…Epithelial cell induction of apoptosis is canonically regarded as a means through which the host can restrict pathogen replication in infected cells, without loss of membrane integrity and the secretion of DAMPs leading to hyper-inflammatory responses by the immune system (207). Many respiratory pathogens compromise pulmonary tolerance through the inhibition of apoptotic cell death and the upregulation of more inflammatory forms of cell death, such as necrosis, oncosis, or pyroptosis (208)(209)(210)(211). The hyper-inflammatory response to such forms of cell death is affected by immune cells sensing DAMPs.…”

Solid Tumor Immunotherapy with T Cell Engager‐Armed Oncolytic Viruses

“…). Recently, the clinical candidate EnAd was found to kill independently of p53 and caspase; instead, infected cells were characterized by high surface exposure of calreticulin and release of the immunomodulatory molecules HSP70, ATP, and HMGB1 in a death mechanism reminiscent of oncosis . In vitro, EnAd infection led to stimulation of dendritic cells and CD4 + T cells in mixed tumor‐leukocyte cell reactions .…”