IFNA1 and neoplasm: During an antitumor immune response, IFN‐I or DNA leaked from tumor cells also provoked IFN‐I signaling in immune cells, especially DCs, to form a positive feedback loop of such signaling.[33] Indeed, DCs cocultured with Smad4KO PDAC cells, but not WT cells, exhibited upregulation of Ifnα and Ifnβ expression (Figure 5F), and anti‐IFNAR1 pretreatment abolished such effect (Figure 5G).