RIPK3 promotes adenovirus type 5 activity

Abstract

Oncolytic adenoviral mutants infect human malignant cells and replicate selectively within them. This induces direct cytotoxicity that can also trigger profound innate and adaptive immune responses. However, the mechanism by which adenoviruses produce cell death remains uncertain. We previously suggested that type 5 adenoviruses, including the E1A CR2 deletion mutant dl922-947, might induce a novel form of programmed death resembling necroptosis. Here we have investigated the roles of core necrosis proteins RIPK1, RIPK3 and MLKL in the cytotoxicity of dl922-947 and other adenovirus serotypes. By electron microscopy, we show that dl922-947 induces similar necrotic morphology as TSZ treatment (TNF-α, Smac mimetic, zVAD.fmk). However, dl922-947-mediated death is independent of TNF-α signalling, does not require RIPK1 and does not rely upon the presence of MLKL. However, inhibition of caspases, specifically caspase-8, induces necroptosis that is RIPK3 dependent and significantly enhances dl922-947 cytotoxicity. Moreover, using CRISPR/Cas9 gene editing, we demonstrate that the increase in cytotoxicity seen upon caspase inhibition is also MLKL dependent. Even in the absence of caspase inhibition, RIPK3 expression promotes dl922-947 and wild-type adenovirus type 5 efficacy both in vitro and in vivo. Together, these results suggest that adenovirus induces a form of programmed necrosis that differs from classical TSZ necroptosis.

Chlorpyrifos Suppresses Neutrophil Extracellular Traps in Carp by Promoting Necroptosis and Inhibiting Respiratory Burst Caused by the PKC/MAPK Pathway

“…The FOLE-induced overproduction of ROS can promote RIP1-dependent and caspase 8-licensed necroptosis [46]. The inhibition of caspase 8 induced RIPK3-dependent necroptosis [47]. In our study, the treatment of blood neutrophils with CPF can increase the levels of CYLD, RIP3, and MLKL and reduce the levels of caspase 8 suggesting that CPF induced necroptosis in neutrophils.…”

The Oncolytic Virus dl922-947 Triggers Immunogenic Cell Death in Mesothelioma and Reduces Xenograft Growth

“…Previous studies report that cell death induced by dl 922-947 does not rely on classical apoptosis but rather shows features of regulated necrosis, although the underlying mechanisms still need to be clarified (37). Importantly, a paramount property of programmed necrosis is the ability to engage the host resident immune cells (38).…”

“…OVs trigger cell demise through various mechanisms engaging different host cell death machineries and depending on the virus or the host cells or by a combination of both. The mechanisms whereby dl 922-947 induces cell death are only partially being revealed; recently, features of programmed necrosis different from canonical necroptosis have been described (37). However, beyond the underlying pathways, it is now recognized that a paramount mechanism of action of OVs is their ability to act as in situ cancer vaccines, releasing tumor antigens and activating a robust tumor-specific immune response, which is one of the major goals of current cancer therapies (47, 48).…”

New Insights to Adenovirus-Directed Innate Immunity in Respiratory Epithelial Cells

“…It was predicted that this E3 deletion might make this virus more sensitive to the antiviral effects of TNF-α. However, recent studies have shown that that dl 922-947 induces a novel form of TNF-α-independent programmed cell death, which differs from classical apoptosis and necroptosis pathways [186]. Our studies suggest an alternative mechanism involving the interaction between HAdV-C-encoded RIDα and ORP1L illustrated in Figure 4.…”