A link between type I IFN and immunotherapy responses has also been identified in TNBC and melanoma, where use of an IFN inducer was able to sensitize mice to checkpoint-based immunotherapy.33,43 Our observation that type I IFN or IFN inducers stimulate IRF9 expression in human TNBC cell lines further supports the implementation of IFN-based therapeutics into the clinic. Here, IRF9 is linked to melanoma.