SMAC-armed oncolytic virotherapy enhances the anticancer activity of PD1 blockade by modulating PANoptosis.

Background: Oncolytic viruses (OVs) are increasingly recognized as promising tools for cancer therapy, as they selectively infect and destroy tumor cells while leaving healthy cells unharmed. Despite considerable progress, the limited therapeutic efficacy of OV-based virotherapy continues to be a significant challenge in cancer treatment.

Methods: The SMAC/DIABLO gene was inserted into the genome of vesicular stomatitis virus (VSV) to generate VSV-S. Head and neck squamous cell carcinoma (HNSCC) cell lines and orthotopic mouse models were employed for research. Morphological changes were observed using both light microscopy and transmission electron microscopy. Molecular alterations were analyzed through Western blotting and ELISA kits. The tumor secretome was characterized using a combination of biotinylation and LC-MS analysis. Immune cell changes were evaluated by flow cytometry and immunohistochemistry.

Results: Compared to its parental virus, VSV-S not only increases apoptosis by overexpressing SMAC during VSV infection but also triggers elevated levels of PANoptosis (pyroptosis, apoptosis, and necroptosis) in HNSCC cells via activation of caspase-1/gasdermin D (GSDMD) signaling. As a result, VSV-S-induced PANoptosis promotes CD8⁺ T cell tumor infiltration and enhances their cytotoxic capacity, eventually potentiating T cell-mediated antitumor immunity. Moreover, VSV-S reduces PDL1 levels in HNSCC cells and, in combination with PD1 blockade, produces a more potent antitumor effect than either therapy alone.

Conclusions: Our findings demonstrate that the combination of VSV-S and PD1 blockade offers a synergistic therapeutic strategy for HNSCC, supporting the advancement of VSV-based virotherapy as a promising strategy to improve outcomes for HNSCC patients.