CIITA and melanoma: In experiments inspired by these observations, we found that the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP) effectively induced death of both IFN-responsive HCmel12 Ciita-KO and IFN-unresponsive HCmel12 Jak1-KO melanoma cells in vitro (Fig. 4d,e and Extended Data Fig. 9f,g).