Abstract 5406: Chemosensitization of melanoma by use of the minimalistic nonviral MIDGE expression system for improved TNF-alpha expression in vitro and in vivo

Abstract

Abstract Melanomas are often refractory towards chemotherapy. Tumor necrosis factor alpha (TNF-alpha) is known for its strong chemosensitizing potential. However, to exploit this potential, high doses of TNF-alpha are required, which are often associated with severe toxicities limiting the clinical applicability. Alternatively, TNF-alpha can be generated at high level at the tumor site using local application of gene therapy. To achieve this, we employed the nonviral MIDGE vector system for significantly improved TNF-alpha expression. The minimalistic immunologically defined gene expression (MIDGE; Mologen AG, Berlin, Germany) vector system is a linear DNA molecule that is depleted of bacterial backbone, antibiotic resistance sequences and CpG motifs, which significantly reduces its size. In our in vitro experiments using equimolar amounts of luciferase expressing MIDGE vector or plasmid we observed significant up to 13-fold increased MIDGE vector mediated expression in transfected human A375, MeWo and SKMEL-28 melanoma cells. Accordingly the FACScan analysis revealed improved transfection efficiency of MIDGE vectors. We used the MIDGE vector to efficiently express TNF-alpha in human A375 melanoma cells in vitro. The MIDGE vector generated significantly higher TNF-levels in comparison to plasmid-mediated expression. The in vivo transfer of the TNF-expressing MIDGE vector into A375 melanomas by intratumoral nonviral jet-injection resulted in efficient high level cytokine expression, which was time and vector-dose dependent. Importantly, this high level TNF-expression does not lead to TNF-alpha release into the circulation and does not cause increase in body temperature or losses in body weight. The MIDGE-mediated TNF-alpha expression mediates efficient chemosensitization in the melanoma xenotransplant bearing nude mice by improving the in vivo chemotherapy with vindesine. This is reflected by significant tumor growth inhibition. The study demonstrates the superiority of the MIDGE vector system for nonviral local gene therapy approaches that might be translated into clinical applications. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5406. doi:10.1158/1538-7445.AM2011-5406