Nonviral therapeutic cell vaccine mediates potent antitumor effects

Therapeutic vaccination of mice bearing melanoma tumors with our genetically modified tumor cells, via DOTAP/GM-CSF lipoplexes, results in >85% tumor growth inhibition. These fresh transfected cells (irradiated, frozen and thawed) are able to produce high amounts of GM-CSF transgene (>200 ng/10 6 cells/24 h). After vaccination, significant increases (>eight-fold) in specific antitumor membrane protein IgG1 and IgG2a are obtained only in groups vaccinated with GM-CSF-producing cells, where also the highest rates of tumor inhibition, and significantly delayed mice death ( P < 0.05), are observed. The antitumor response obtained is long-lasting in survivors (GM-CSF-group) from 6 months after the first tumor challenge, and a full 100% of mice survived to a second tumor challenge. All these results suggest that antitumor cell vaccines engineered by nonviral procedures are suitable for use as therapeutic vaccines with potential clinical applications.