STING1 and neoplasm: We found that the effect of reduced tumor growth in LysMcrePP2Acfl/fl mice was abolished when cGAS was deficient in SB28 (Figure 3C) or B16 (Supplemental Figure 6B) tumors, suggesting that tumor cGAMP production, which is responsible for STING activation in host macrophages, is required for PP2Ac-mediated regulation of macrophage tumor immunity.