IFNB1 and neoplasm: To formally test this hypothesis, we performed intratumoral injection of purified recombinant IFN-β protein into WT and Stingfl/fl/Tek-Cre mice, and found that IFN-β administration significantly inhibited tumor growth in WT mice, but not in Stingfl/fl/Tek-Cre and Ifnar–/– mice (Figure 3, H–J, and Supplemental Figure 3G).