These modifications involve expressing immunostimulatory heterologous genes, such as interleukin-12 (IL-12) [16], granulocyte/macrophage colony-stimulating factor (GM-CSF) [17], interferon-gamma (IFN-γ), interleukin-2 (IL-2), or tumor necrosis factor-alpha (TNF-α) [15] in various human cancers. The gene discussed is CSF2; the disease is cancer.