Reestablishment of p53/Arf and interferon- β pathways mediated by a novel adenoviral vector potentiates antiviral response and immunogenic cell death

Late stage melanoma continues to be quite difficult to treat and new therapeutic approaches are needed. Since these tumors often retain wild-type p53 and have a strong immunogenic potential, we developed a gene transfer approach which targets these characteristics. Previously, we have shown that combined gene transfer of p19Arf and interferon-beta (IFN β ) results in higher levels of cell death and superior immune-mediated antitumor protection. However, these experiments were performed using B16 cells (p53wt) with forced expression of the adenovirus receptor and also the mechanism of death was largely unexplored. Here we take advantage of a novel adenoviral vector (AdRGD-PG), presenting an RGD-modified fiber as well as a p53-responsive promoter, in order to investigate further potential benefits and cell death mechanisms involved with the combined transfer of the p19Arf and IFN β genes to the parental B16 cell line. Simultaneous p19Arf and IFN β gene transfer is more effective for the induction of cell death than single gene treatment and we revealed that p19Arf can sensitize cells to the bystander effect mediated by secreted IFN β . Strikingly, the levels of cell death induced upon activating the p53/p19Arf and interferon pathways were higher in the presence of the AdRGD-PG vectors as compared to approaches using pharmacological mimetics and this was accompanied by the upregulation of antiviral response genes. Only combined gene transfer conferred immunogenic cell death revealed by the detection of key markers both in vitro and in vivo. Finally, whole-genome transcriptome analysis revealed unique expression profiles depending on gene function, including immune activation, response to virus and p53 signaling. In this way, cooperation of p19Arf and IFN β activates the p53 pathway in the presence of an antiviral response elicited by IFN β , culminating in immunogenic cell death.