Conclusion
Intratumoral jet injection of plasmid DNA led to efficient LacZ reporter gene expression in all patients. No side effects were experienced, supporting safety and applicability of this novel nonviral approach. A next step with a therapeutic gene product should determine antitumor efficacy of jet-injection gene transfer.
Purpose
This phase I clinical trial evaluated safety, feasibility, and efficiency of nonviral intratumoral jet-injection gene transfer in patients with skin metastases from melanoma and breast cancer. Experimental design: Seventeen patients were enrolled. The patients received five jet injections with a total dose of 0.05 mg beta-galactosidase (LacZ)-expressing plasmid DNA (pCMVbeta) into a single cutaneous lesion. Clinical and laboratory safety monitoring were done. Systemic plasmid clearance was monitored by quantitative real-time PCR of blood samples throughout the study. All lesions were resected after 2 to 6 days. Intratumoral plasmid DNA load, DNA distribution, and LacZ expression was analyzed by quantitative real-time PCR, quantitative reverse transcription-PCR, Western blot, immunohistochemistry, and 5-bromo-4-chloro-3-indolyl-beta-D-galactoside staining.
Results
Jet injection of plasmid DNA was safely done in all patients. No serious side effects were observed. Thirty minutes after jet injection, peak plasmid DNA levels were detected in the blood followed by rapid decline and clearance. Plasmid DNA and LacZ mRNA and protein expression were detected in all treated lesions. Quantitative analysis revealed a correlation of plasmid DNA load and LacZ-mRNA expression confirmed by Western blot. Immunohistochemistry and 5-bromo-4-chloro-3-indolyl-beta-D-galactoside staining showed LacZ-protein throughout the tumor. Transfected tumor areas were found close and distant to the jet-injection site with varying levels of DNA load and transgene expression.