CD47 crosslinking with different mAbs has been demonstrated to induce apoptosis in cancer cells in a manner felt to be similar to CD47 binding another natural ligand, Thrombospondin.32, –34 The anti-CD47 used in our study, Hu5F9-G4, has been demonstrated to block the interaction between CD47 and SIRPα.14 There have been no studies to suggest that Hu5F9-G4 either blocks or mimics CD47–thrombospondin interaction. This evidence concerns the gene SIRPA and cancer.