Research Progress of CD47-SIRPα Signaling Axis as An Innate Immune Checkpoint in Cancer

Immune checkpoint inhibitors, including those targeting CTLA-4/B7 and PD-1/PD-L1 inhibitory pathways, are now available for clinical use on cancer patients. Other interesting checkpoint inhibitors are currently under the development. CD47 is a protein broadly expressed on the surface of normal cells and often overexpressed in cancer cells, and its receptor is the myeloid inhibitory immunoreceptor SIRPα. Blocking CD47-SIRPα interactions has been shown to promote the destruction of cancer cells by phagocytes, including macrophages and neutrophils. Furthermore, there is growing evidence that targeting CD47-SIRPα axis may also promote antigen-presenting cell function and thereby stimulate T cell-mediated anti-cancer immunity. In summary, with the clinical studies about CD47-SIRPα checkpoint inhibitors expected within the coming years, this is an exciting and rapidly developing field.