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The prognosis and response to conventional therapies of malignant melanoma inversely correlate with disease progression. With increasing thickness, melanomas acquire metastatic potential and become inherently resistant to radiotherapy and chemotherapy. These harsh realities mandate the design of improved therapeutic modalities, especially those targeting metastases. To develop an approach to effectively treat this aggressive disease, we constructed a conditionally replication-competent adenovirus in which expression of the adenoviral E1A gene, necessary for replication, is driven by the cancer-specific promoter of progression-elevated gene-3 (PEG-3) and which simultaneously expresses mda-7/IL-24 in the E3 region of the adenovirus (Ad.PEG-E1A-mda-7), a cancer terminator virus (CTV). This CTV produces large quantities of MDA-7/IL-24 protein as a function of adenovirus replication uniquely in cancer cells. Infection of Ad.PEG-E1A-mda-7 (CTV) in normal human immortal melanocytes and human melanoma cells demonstrates cancer cell-selective adenoviral replication, mda-7/IL-24 expression, growth inhibition and apoptosis induction. Injecting Ad.PEG-E1A-mda-7 CTV into xenografts derived from MeWo human metastatic melanoma cells in athymic nude mice completely eliminated not only primary treated tumors but also distant non-treated tumors (established in the opposite flank), thereby implementing a cure. These provocative findings advocate potential therapeutic applications of this novel virus for treating patients with advanced melanomas with metastases.

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Abstract-The use of viral vectors for vascular gene therapy targeted at the endothelium is limited by the promiscuous tropism of vectors and nonspecificity of viral promoters, resulting in high-level transgene expression in multiple tissues.To evaluate suitable endothelial cell (EC)-specific promoters for vascular gene therapy, we directly compared the ability of the fms-like tyrosine kinase-1 (FLT-1), intercellular adhesion molecule-2 (ICAM-2), and von Willebrand factor (vWF) promoters to drive EC-restricted transcription after cloning into adenoviral vectors upstream of lacZ. Vastly different expression profiles were observed. Whereas both FLT-1 and ICAM-2 promoters generated transgene expression levels similar to cytomegalovirus in ECs in vitro, vWF expression levels were extremely low. Analysis of non-EC types revealed that ICAM-2 but not FLT-1 evoked leaky transgene expression, thus identifying FLT-1 as the most selective promoter. With an ex vivo human gene therapy model, the FLT-1 promoter demonstrated EC-specific transgene expression in intact human vein but no detectable expression from infected exposed smooth muscle cells in EC-denuded vein. Furthermore, when adenoviruses were systemically administered to mice, the FLT-1 promoter demonstrated extremely low-level gene expression in the liver, the major target organ for adenoviral transduction in vivo. This study highlights the potential of using the FLT-1 promoter for local and systemic human gene therapy in hypertension and its complications.