M1 macrophages kill and remove tumor cells by activating pro-inflammatory cytokines (e.g., tumor necrosis factor alpha, TNF-α) in the tumor microenvironment, recruiting or activating cytokines such as interferon (IFN)-γ and interleukin (IL)-12 to infiltrate immune effector cells into the tumor microenvironment. The gene discussed is TNF; the disease is neoplasm.