Malignant melanoma has one of the most rapidly increasing incidence rates in the U.S. Early detection and surgical excision can be curative, but once the tumor spreads beyond the skin it is one of the most deadly forms of cancer. There are currently no completely effective therapies for advanced (metastatic) disease and 10 year survival rates for these patients are very low. The objectives of this proposal are to conduct phase I clinical trials of a new gene therapy approach for the treatment of metastatic melanoma, to monitor for tumor responses attributable to treatment, and develop and characterize in vitro assays which may enable us to identify which patients are most likely to respond to this form of combined immuno-gene therapy. The therapeutic genes selected for use in the clinical trial are the genes for human granulocyte/macrophage colony stimulating factor (GM-CSF) and the gene for the superantigen staphylococcus enterotoxin B (SEB). In on-going preclinical trials conducted by one of the coinvestigators of this proposal, in a private veterinary oncology clinic, this combination of therapeutic genes has been shown to be more effective at inducing clinically significant tumor immunity than either gene used alone and more effective than other combinations of genes tested. The method used for gene transfection, polycationic lipid mediated gene transfection, has been tested extensively in the preclinical trials and found to be safe and effective. The phase I clinical trial is a dose escalation study designed to determine the safety and potential toxicities associated with the direct combination DNA injections of cutaneous melanoma metastases. Although the primary goal of the trial is to assess safety and toxicity, careful clinical analyses of treated and untreated tumors will allow the determination of whether the proposed treatments have an effect on local and distant metastases. In addition, in vitro immunologic assays which have proven to be indicative of development of protective tumor immunity in preclinical studies will be conducted concurrently with the clinical evaluations to determine if they have predictive value in identifying those patients which will benefit from this treatment approach. An improved understanding of how this treatment leads to the elimination of tumor tolerance and the development of immunity may enable us design more effective strategies for the use of these treatments in the clinical setting.
