Sensitization of tumor necrosis factor alpha-resistant human melanoma by tumor-specific in vivo transfer of the gene encoding endothelial monocyte-activating polypeptide II using recombinant vaccinia virus

Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine with potent experimental antitumor activity. Its clinical use in cancer treatmen t is severely limited by its considerable toxicity after systemic administr ation, and it is currently confined to isolated limb and organ perfusion se ttings. In this report, we introduce a novel concept of TNF-alpha-based gene therap y using the TNF-sensitizing properties of endothelial cell monocyte activat ing polypeptide II (EMAP-II). We hypothesized that transfer of the EMAP-II gene into established TNF-resistant human melanomas would render these tumo rs sensitive to subsequent systemic TNF-alpha treatment. To achieve tumor selective gene delivery, we constructed a recombinant vacc inia virus encoding the human EMAP-II gene (vvEMAP). In vitro transfection of human melanoma cells led to the production of EMAP-II by these cells. Su pernatants of vvEMAP-transfected tumor cells mediated the induction of tiss ue factor in endothelial cells. We characterized the pattern of gene expression after systemic administrati on of a recombinant vaccinia virus encoding a reporter gene in a murine in vivo model of s.c. human melanoma. Gene expression in tumor tissue was incr eased 100-fold as compared with normal tissue, providing evidence for tumor -selective gene delivery. Finally, human melanomas in nude mice were sensitized in vivo by transferri ng the EMAP-II gene using vvEMAP. Subsequent systemic administration of TMF -alpha led to tumor regression and growth inhibition of these previously TN F-resistant tumors (P < 0.05). This approach using gene therapy to sensitize primarily unresponsive tumors toward TNF-alpha may enhance the usefulness of TNF-alpha in clinical treat ment strategies by increasing the window for the therapeutic application of the cytokine, thus reducing the dose necessary for antitumor responses and subsequently reduce toxicity.