Research advances on CD47 in digestive system cancers: from molecular mechanisms to clinical translation.

CD47 is a major innate immune checkpoint molecule that interacts with signal regulatory protein α (SIRPα) to deliver a "don't eat me" signal and restrain macrophage-mediated phagocytosis. Accumulating evidence indicates that dysregulated CD47 expression is associated with immune escape, treatment resistance, and adverse clinicopathological features in several digestive system cancers, although the strength of these associations varies across tumor types. This narrative review provides an integrative overview of CD47 structure, ligand interactions, signaling and immune-regulatory functions, and summarizes reported expression patterns and available evidence regarding regulatory mechanisms and relevant mechanistic contexts in esophageal, gastric, colorectal, hepatocellular, pancreatic, and biliary tract cancers. We further review therapeutic strategies targeting the CD47-SIRPα axis, including anti-CD47 antibodies, SIRPα fusion proteins, bispecific antibodies, and emerging cell-based and nanotechnology-based platforms, with particular attention to recent clinical developments. Finally, we critically discuss translational challenges, including hematologic toxicity and antigen sink, assay standardization and biomarker selection, resistance mechanisms, optimization of combination regimens, and the need for prospective validation of hypothesis-generating biomarker signals. By integrating recent 2025-2026 clinical developments with mechanistic and engineering advances, including lessons from unsuccessful or discontinued clinical programs, this review provides a balanced perspective on the opportunities and remaining barriers to the clinical translation of CD47-directed therapy in digestive system cancers.