As an important aim in the project, we have generated substantial preliminary data showing infectability of human hepatocellular carcinoma (HCC) cell lines, as well as other tumor cell lines, and patient-derived material with our oncolytic VSV-NDV vector. EC50 data indicate heterogeneity of susceptibility to oncolysis, although in general, all cell lines and primary tumor cells were in the range considered to be permissive and susceptible to VSV-NDV-mediated oncolysis. Furhtermore, we demonstrated that cell death via VSV-NDV infection is immunogenic in nature, as shown by analysis of established immunogenic cell death markers.
The overarching aim of the DCanVAX project was to build upon preliminary research conducted within the main ERC Starting Grant project, ONCO-VAX, where it was shown in the mouse system that VSV-NDV-based tumor oncolysates could efficiently activate dendritic cells (DCs) and load them with individualized tumor antigens, forming the basis of a broad-acting, but personalized, DC-based cancer vaccine. As a first step towards bridging this approach with a potential clinical application, we first established a method for short-term cultivation of primary tumor material obtained from clinical resections, and furthermore developed a standardized protocol for infected these patient-derived tumor cells in 2D cultures in order to generate the oncolysates needed for activating DCs. We then generated monocyte-derived DCs (moDCs) from human blood and fully characterized them, which turned out to primarily of the type-2 conventional DC (cDC2) -like phenotype. In a next step, we co-cultured these moDCs with human tumor cells that had been previously infected with VSV-NDV and performed phenotypic and functional readouts. We demonstrated that these moDCs take on an activated phenotype according to expression of known DC activation markers, such as CD80, CD86, and MHCII, by flow cytometry analysis, and preliminary data indicated that these DCs are then capable of activating CD8+ T cells in vitro. These data are fully consistent with the findings achieved in the mouse system, thereby validating the concept that ex vivo infection of patient tumor material with oncolytic VSV-NDV serves as an efficient method for generating a personalized DC-based cancer vaccine.