TNF and neoplasm: The fundamentals of cytokine gene therapy relies on the increase of cytokine levels with anti-tumor properties, including interleukin-2 (IL-2), IL-4, IL-6, IL-12, IL-24, interferon-alpha (IFN-α), IFN-γ, IFN-β or tumor necrosis factors (TNF) TNF-α and TNF-β [25].