STAT1 and neoplasm: As summarized before [26], three strategies are utilized by tumor cells to cope with the anti-tumor effects of IFN-γ: i) losing the sensitivity to IFN-γ, ii) shifting the signaling pathway from STAT1/IRF1 to rather pro-tumorigenic alternative pathways like STAT3/NF-κB, iii) up-regulation of inhibitory ligands such as PD-L1 and PD-L2.