Feasibility study of gene gun mediated immunotherapy for renal cell carcinoma.

Purpose. Gene modified autologous tumor cell vaccines have demonstrated a p rotective and therapeutic effect in murine tumor model systems. The majorit y of trials to date have used viral methods of gene transfer for vaccine co nstruction. An alternative approach to transfer genes into tumor cells is t o use the gene gun, which is a physical method of gene transfection that pr oduces high levels of gene expression without viral agents. We establish th e feasibility of generating cytokine secreting autologous renal tumor cell vaccines for use in gene therapy for metastatic renal cell carcinoma. Materials and Methods: We obtained 1 cm.(3) tumor tissue from 12 patients u ndergoing resection of primary or metastatic renal cell carcinoma. The tumo r was disaggregated and placed in culture. The phenotype of the primary ren al cell lines was established by microscopy and immunohistochemistry. The 1 x 10(7) lethally irradiated tumor cells were transfected with plasmid deox yribonucleic acid containing the human (h) granulocyte-macrophage colony-st imulating factor (GM-CSF) gene under control of a cytomegalovirus promoter using the gene gun. The hGM-CSF production was assayed by enzyme-linked imm unosorbent assay in the cell culture media 24 hours after transfection. Results: Of 12 tumor samples 8 grew rapidly to produce a mean of 1.8 x 10(8 ) cells after 4 to 5 passages in culture, which was sufficient to produce b etween 24 and 32 vaccines. Immunocytochemistry confirmed that all cultures were almost exclusively renal tumor cells. Gene gun mediated transfection o f lethally irradiated tumor cells resulted in high levels of hGM-CSF produc tion (mean 330 ng./10(6) cells per 24 hours). Conclusions: We have demonstrated the feasibility of producing cytokine sec reting tumor cell vaccines from primary and metastatic human renal tumors, and plan to use this approach in phase I clinical trials of gene therapy fo r metastatic renal cell carcinoma.