CD47 is a novel potent immunotherapy target in human malignancies: current studies and future promises.

Recently, many immunosuppressive checkpoints such as PD-L1, CTLA-4 and CD47, were identified in succession and serve as potential immunotherapy targets in human cancers. Among them, CD47, a 'marker-of-self' protein that is overexpressed broadly across tumor types, is emerging as a novel potent macrophage immune checkpoint for cancer immunotherapy. In this review, we highlight the prominent role of CD47 as a 'don't-eat-me' signal that inhibits macrophage phagocytosis for immune evasion of a tumor and presents the opportunities and challenges for CD47 inhibitors both as monotherapy and in combination treatments for hematological cancers and solid tumors; some of these agents are currently in clinical trials.