The overall potential of CD47 in cancer immunotherapy: with a focus on gastrointestinal tumors.

: CD47 is an anti-phagocytic ('don't eat me') signal overexpressed in many malignant diseases. It acts as myeloid immune checkpoint and thus has prognostic and therapeutic implications.: This review presents and discusses the currently available data on the prognostic role and therapeutic value of CD47 in gastrointestinal tumors.: CD47 is overexpressed on the great majority of gastrointestinal tumors, cancer stem cells and circulating tumor cells. Overexpression of CD47 usually predicts a negative prognosis and seems to contribute to cancer immune evasion. The inhibition of CD47 has shown impressive results in clinical trials in hematologic malignancies. However, for gastrointestinal tumors only preclinical data is available. Inhibition of this myeloid immune checkpoint may yield great clinical benefit due to the abundance of myeloid effector cells. However, due to the ubiquitous expression of CD47 and the resulting antigen sink, vast amounts of antibody are required in order to reach therapeutic concentrations. QPCTL inhibitors blocking post-translational modification of CD47 protein may be a solution to this problem.