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The Molecular Mechanism of the CD47-SIRP$\alpha$ Signaling Axis
The therapeutic potential of CD47 is rooted in its role as a universal marker of "self." Under normal physiological conditions, CD47 is expressed on healthy cells, where it binds to Signal Regulatory Protein Alpha (SIRP$\alpha$) on the surface of macrophages and dendritic cells.
This interaction triggers a signaling cascade that inhibits the macrophage’s pro-phagocytic machinery, specifically by recruiting phosphatases that block the accumulation of myosin IIA at the phagocytic synapse. Essentially, this interaction sends a "don't eat me" signal, protecting healthy cells from auto-immune destruction.
However, cancer cells—across both hematological and solid tumors—hijack this system by overexpressing CD47. This allows them to thrive in an environment rich with immune cells that would otherwise eliminate them. Targeting this axis involves using monoclonal antibodies or decoy receptors to physically block the CD47-SIRP$\alpha$ binding. This "unmasks" the cancer cell, allowing "eat me" signals (such as calreticulin) to trigger phagocytosis. In 2026, research has shifted…