Increase of In Vivo Antitumoral Activity by CD40L (CD154) Gene Transfer Into Pancreatic Tumor Cell-Dendritic Cell Hybrids

OBJECTIVES: Fusion of dendritic cells (DC) with tumor cells is an approach in immunotherapy combining antigenicity and capacity of antigen presentation to activate T cells for the induction of tumor-specific cytotoxic immunity. Although there have been reports of clinical benefit, response rates have been limited and further improvements are warranted. METHODS: We used murine DC and a novel protocol for an effective fusion of those cells with the murine pancreatic cell line Panc02. RESULTS: We observed 2 events: only moderate in vitro and in vivo cytotoxicity of tumor cell/DC hybrids and a down-regulation of costimulatory molecules on fused cells. Therefore, we transfected tumor cell/DC hybrids with an adenovirus expressing CD154 to improve DC activation and generating antitumor immune response without the need of CD4 T cells. High CD154 expression could be obtained by transfection of DC and Panc02 cells prior fusion. Furthermore, vaccination with CD154-transfected tumor cell/DC hybrid led to a significantly increased induction of cytotoxic T cells in vitro and to an improved antitumoral effect in an orthotopic in vivo mouse model. CONCLUSIONS: CD154-transfected tumor cell/DC hybrids are a promising approach to increase the efficiency of antitumoral response.