We determined a clear antitumor effect of IL-12 plasmid DNA against an experimental murine tumor, which was associated with shift to a Th1-type cytokines profile, with expression of IL-2, IL-12 and IFN-γ cytokines and reduced expression of IL-10, IL-4 and TGF-β1 cytokines. The gene discussed is IL10; the disease is neoplasm.