Preclinical full-scale evaluation of dendritic cells transfected with autologous tumor-mRNA for melanoma vaccination.

Most cancer vaccines to date have made use of common tumor antigens or allogenic cancer cell lines. The majority of tumor antigens may, however, be unique patient-specific antigens. Dendritic cells (DCs) are the most potent antigen-presenting cells known. The present report is a full-scale preclinical evaluation of autologous DCs transfected with autologous tumor-mRNA (tDCs) for vaccination in malignant melanoma. By using autologous tumor-mRNA, we intend to make the DCs present a broad spectrum of tumor-associated antigens relevant to each individual patient. Previously, we have described effective methods for mRNA-transfection into DCs by square-wave electroporation and for generating large numbers of DCs. Here, we demonstrate the ability of tDCs, made under full-scale vaccine conditions, to generate in vitro T-cell responses specific for antigens encoded by the transfected tumor-mRNA. T-cell proliferation assays demonstrated tDC-specific responses for all six patients tested. Responses were further studied by IFNgamma ELISPOT and Bioplex cytokine assays (two patients) and by experiments on isolated CD4(+) and CD8(+) T cells, including HLA-blockage (one patient). Moreover, we describe the results of extensive tumor-RNA analysis using Agilent Bioanalyser, a method that we have implemented in the clinical protocol. Based on this preclinical evaluation, a vaccine trial has been started.