TRANSDUCTION OF MURINE AND HUMAN TUMORS USING RECOMBINANT ADENOVIRUS VECTORS

Background: Most cytokine-based cancer gene therapy clinical trials ha ve used labor-intensive, retrovirus-mediated strategies resulting in u npredictable gene expression. Recombinant AdV vectors were evaluated f or easier, more reproducible gene transfer into 12 human melanoma, 2 m urine fibrosarcomas. and 8 other tumor cell lines. Methods: AdV vector s contained a reporter (Escherichia coli beta-galactosidase or firefly luciferase) or cytokine gene (human interleukin-2 [IL-2] or IL-7). Tr ansduction efficiencies and expression levels were assessed by histoch emical staining, flow cytometry, polymerase chain reaction, fluorometr y, and enzyme-linked immunosorbent assay. Tumorigenicity was determine d by subcutaneous injection of cells into syngeneic mice. Results: All cell lines studied were transduced with AdV, Most cell lines exhibite d 100% transduction efficiencies (by flow cytometry) at multiplicities of infection (MOI) epsilon 10. Gene expression correlated linearly wi th MOI, but a cytopathic effect was observed at MOI > 100 with all vec tors. Nanogram gene expression levels were routinely achieved, Irradia tion (30 Gy) minimally affected expression levels. Tumorigenicity of A dV-IL-2-transduced fibrosarcoma cells in mice was inversely related to IL-2 production. A majority of mice that rejected their tumor challen ge were immune to tumor rechallenge, Conclusions: EI-deleted AdV vecto rs may prove useful in generating tumor vaccines ex vivo with high, tr ansient cytokine expression levels.