RAPID ADENOVIRAL TRANSDUCTION OF FRESHLY RESECTED TUMOR EXPLANTS WITHTHERAPEUTICALLY USEFUL GENES PROVIDES A RATIONALE FOR GENETIC IMMUNOTHERAPY FOR COLORECTAL-CANCER

To develop protocols for the molecular immunotherapy of colorectal can cer, we compared the efficacy of three separate classes of therapeutic genes in induce antitumour responses in a murine colorectal cell mode l. Thus, the effects of two cytokines (IL-2 and GM-CSF) were compared with those of a costimulatory gene (B7.1) and a suicide gene (HSCtk). The rank order of efficacy against primary tumour growth was HSCtk[GCV ], B7.1 > puro, IL-2 > GM-CSF, neo whereas the order of efficacy in in ducing antitumour immunituy was GM-CSF, IL-2, >B7.1, HSVtk[GCV]> puro, neo in a prophylatctic vaccination model. To exploit these data in a clinically relevant and realistic way, we also demonstrated that color ectal tumours can reproducibly be explanted and established in short-t erm culture. Finally, a rapid transduction protocol has been developed by which using adenoviral vectors, as many as 90% of the cells in the se fresh tumour explants can be engineered to express high levels of t he clinically relevant genes (GM-CSFor IL-2) within 1-2 weeks of surge ry. Adenovirus-mediated gene delivery was reproducibly and significant ly more efficient than retroviral transduction using the MFG-beta-Gal retroviral vector over the time-frame of importance for vaccination. H ence, combination of the animal model data with the ex vivo modificati on protocol suggests that vaccination of colorectal patients of the ap propriate stage will be possible and effective.