Virus-mediated oncolysis induces danger signal and stimulates cytotoxic T-lymphocyte activity via proteasome activator upregulation

Dendritic cells (DCs) are the most potent antigen-presenting cells and acquire cellular antigens and danger signals from dying cells to initiate antitumor immune responses via direct cell-to-cell interaction and cytokine production. The optimal forms of tumor cell death for priming DCs for the release of danger signals are not fully understood. OBP-301 (Telomelysin) is a telomerase-specific replication-competent adenovirus that induces selective E1 expression and exclusively kills human cancer cells. Here, we show that OBP-301 replication produced the endogenous danger signaling molecule, uric acid, in infected human tumor cells, which in turn stimulated DCs to produce interferon-gamma (IFN-gamma) and interleukin 12 (IL-12). Subsequently, IFN-gamma release upregulated the endogenous expression of the proteasome activator PA28 in tumor cells and resulted in the induction of cytotoxic T-lymphocytes. Our data suggest that virus-mediated oncolysis might be the effective stimulus for immature DCs to induce specific activity against human cancer cells.