Preclinical development of human granulocyte-macrophage colony-stimulatingfactor-transfected melanoma cell vaccine using established canine cell lines and normal dogs

Tumor vaccines and gene therapy have received significant attention as mean s of increasing cellular and humoral immune responses to cancer. We conduct ed a pilot study of seven research dogs to determine whether intradermal in jection of canine tumor cells transfected via the Accell particle-mediated gene transfer device with the cDNA for human granulocyte-macrophage colony- stimulating factor (hGM-CSF) would generate biologically relevant levels of protein and result in demonstrable histological changes at sites of vaccin ation. Tumor cell vaccines of 10(7) irradiated canine melanoma cells were n ontoxic, safe, and well tolerated. No significant alterations in blood chem istry values or hematological profiles were detected. A histological review of control vaccine sites revealed inflammatory responses predominated by e osinophils, whereas vaccine sites with hGM-CSF-transfected tumor cells had an influx of neutrophils and macrophages. Enzyme-linked immunosorbent assay s of skin biopsies from vaccine sites had local hGM-CSF production (8.68-16 .82 ng/site of injection) at 24 hours after injection and detectable levels (0.014-0.081 ng/site) for less than or equal to 2 weeks following vaccinat ion. Flow cytometric analysis of hGM-CSF-transfected cells demonstrated les s than or equal to 25% transfection efficiency, and hGM-CSF levels obtained during time-course assays demonstrated biologically relevant levels for bo th irradiated and nonirradiated samples. These data demonstrate the in vivo biological activity of irradiated hGM-CSF-transfected canine tumor cells a nd help provide evidence for a valid translational research model of sponta neous tumors.