Oncolytic Parapoxvirus induces Gasdermin E-mediated pyroptosis and activates antitumor immunity

The advantage of oncolytic viruses (OV) in cancer therapy is their dual effect of directly killing tumours while prompting anti-tumour immune response. Oncolytic parapoxvirus ovis (ORFV) and other OVs are thought to induce apoptosis, but apoptosis, being the immunogenically inert compared to other types of cell death, does not explain the highly inflamed microenvironment in OV-challenged tumors. Here we show that ORFV and its recombinant therapeutic derivatives are able to trigger tumor cell pyroptosis via Gasdermin E (GSDME). This effect is especially prominent in GSDME-low tumor cells, in which ORFV-challenge pre-stabilizes GSDME by decreasing its ubiquitination and subsequently initiates pyroptosis. Consistently, GSDME depletion reduces the proportion of intratumoral cytotoxic T lymphocytes, pyroptotic cell death and the success of tumor ORFV virotherapy. In vivo, the OV preferentially accumulates in the tumour upon systemic delivery and elicits pyroptotic tumor killing. Consequentially, ORFV sensitizes immunologically 'cold' tumors to checkpoint blockade. This study thus highlights the critical role of GSDME-mediated pyroptosis in oncolytic ORFV-based antitumor immunity and identifies combinatorial cancer therapy strategies. Oncolytic viruses are able to target tumours and thought to induce apoptosis while remodelling the tumour immune microenvironment. Here authors show in an oncolytic parapoxvirus ovis model that pyroptosis, a highly immunogenic Gasdermin-E-dependent cell death mechanism, is the dominant cell death pathway during virotherapy.

Automated summary

The advantage of oncolytic viruses in cancer therapy lies in their ability to kill tumors directly and induce anti-tumor immune response. This study shows that oncolytic parapoxvirus ovis can trigger tumor cell pyroptosis via GSDME, which plays a critical role in ORFV-based antitumor immunity and sensitizes "cold" tumors to checkpoint blockade.