Cytokine-armed vaccinia virus promotes cytotoxicity towards pancreatic carcinoma cells
Pancreatic ductal adenocarcinoma (PDAC) remains a particularly aggressive disease with few effective treatments. The PDAC tumor immune microenvironment (TIME) is known to be immune suppressive. Oncolytic viruses can increase tumor immunogenicity via immunogenic cell death(ICD). We focused on tumor-selective (vvDD) and cytokine-armed Western-Reserve vaccinia viruses (vvDD-IL2, vvDD-IL15) and infected carcinoma cell lines as well as patient-derived primary PDAC cells. In co-culture experiments, we investigated the cytotoxic response and the activation of human natural killer cells (NK). Infection and virus replication were assessed by measuring virus encoded YFP. We then analyzed intracellular signaling processes and oncolysis via in-depth proteomic analysis, immunoblotting and TUNEL assay. Following the co-culture of mock or virus infected carcinoma cell lines with allogenic PBMCs or NK cell lines, CD56+ NK cells were analyzed with respect to their activation, cytotoxicity and effector function. Both, dose- and time-dependent release of danger signals following infection was assayed. Viruses effectively entered PDAC cells and emitted YFP signals. Infection resulted in concomitant oncolysis. The proteome showed reprogramming of normally active core signaling pathways in PDAC occurred(e.g. MAPK-ERK signaling). Danger-associated molecular patterns were released upon infection and stimulated co-cultured NK cells for enhanced effector cytotoxicity. NK cell subtyping revealed enhanced numbers and activation of a rare CD56dimCD16dim population. Tumor cell killing was primarily triggered via Fas ligands rather than granule release, resulting in marked apoptosis. Cytokine-armed vaccinia viruses induced NK cell activation and enhanced cytotoxicity towards human PDAC cells in vitro. The cytokine-armed virus targets the carcinoma cells with great potential to modulate the TIME in PDAC.
