IFIT1 and neoplasm: Likewise, mRNA levels of Ifit1 and Ifit2, two type I IFN-stimulated genes (ISGs), were also elevated in Ptgs2−/− tumors (Figure 2D), indicative of enhanced type I interferon (IFN-α/β) signaling, which is central to immune-mediated tumor control (Gajewski et al., 2013; Vesely et al., 2011).