Differentiation towards an M1 macrophage phenotype typically occurs following activation by interferon-γ (IFN-γ), granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor (TNF), or lipopolysaccharide (LPS), resulting in a host defense or tumor resistance phenotype [83,84,85]. This evidence concerns the gene CSF2 and neoplasm.