SIRPG and cancer: To determine whether heightened phagocytosis partly accounts for tumor suppression upon SIRPγ knockdown, we performed an in vivo macrophage depletion assay using clodronate liposomes (41, 42) and found that depletion of macrophages partially rescued the reduction in tumorigenicity of SIRPγ-knockdown cancer cells (Supplemental Figure 10, A–E), supporting the notion that SIRPγ orchestrates tumorigenesis partly through inhibiting phagocytosis.