IRF1 and neoplasm: Several factors have been shown to contribute to tumor cell death in response to IFN-γ, including the expression levels of IRF1 (refs. 46,56), IFN-γ-R57,58, SLFN11 (ref. 47), SOCS1 (ref. 59), Fas/Fas ligand60, TRAIL61, iNOS62 and the production of reactive oxygen species and reactive nitrogen intermediates63.