IFNA1 and neoplasm: Moreover, sustained signaling through IFN-induced pathways has also been associated with resistance to immune checkpoint inhibitors (ICIs) through upregulation of PD-L1, PD-L2, CTLA-4, CIITA, IDO1, CXCL12, non-classical MHC antigens and nitric oxide production in tumor cells, which inhibit the ability of the immune system to recognize these cells [174,175,176,177,178,179,180,181,182].