Viral vector delivery in solid-state vehicles: Gene expression in a murineprostate cancer model

Background: Although there are increasingly more clinical trials involving gene therapy, efficient gene transfer remains a major hurdle to success. To enhance the efficiency of delivery of viral vectors in gene therapy protoc ols, we evaluated the effect of various matrices to act as a vehicle for re combinant virus during intratumoral injection. Methods: The ability of seve ral vehicles (catgut spacer, polyglycolic acid, chromic catgut, and gelatin sponge matrix) to deliver the canarypox virus ALVAC to the cells of the mu rine prostate cancer cell line RM-1 was studied in vitro and in vivo. ALVAC recombinants encoding the murine cytokines interleukin 2 (IL-2), interleuk in 12 (IL-12), and tumor necrosis factor-alpha (TNF-alpha) were used to ass ess enhancement of antitumor activity after intratumoral inoculation. Confi rmatory experiments were conducted by use of another mouse prostate cancer cell line, RM-11, and a mouse bladder cancer cell line, MB-49. All statisti cal tests were two-sided. Results: The gelatin sponge matrix proved to be t he most effective solid-state vehicle for delivering viral vectors to cells in culture. In addition, this matrix statistically significantly enhanced expression of ALVAC-delivered reporter genes in tumor models when compared with fluid-phase delivery of virus (P = .037 for the RM-1 model and P = .03 for the MB-49 model). Statistically significant growth inhibition of estab lished tumors was observed when a combination of the three recombinant ALVA C viruses expressing IL-2, IL-12, and TNF-alpha was delivered with the matr ix in comparison with 1) fluidphase intratumoral injection of the ALVAC rec ombinants, 2) no treatment, or 3) treatment with parental ALVAC tall P<.05) . Conclusions: Viral vector delivery in a solid-state vehicle resulted in i mproved recombinant gene expression in vivo and translated to greater inhib ition of tumor growth in an immunotherapy protocol for heterotopic tumor no dules, The efficient delivery of reporter genes described herein may prove useful in many solid tumor gene therapy protocols.