CD93 (also known as C1q R1, C1q R, C1q RP, MXRA4, ECSM3) is a transmembrane glycoprotein consisting of extracellular domains composed of a C-type lectin domain, an epidermal growth factor (EGF)-like domain, and a heavily glycosylated mucin-like domain (amino acids 24-580), a transmembrane domain (amino acids 581-601), and a short cytoplasmic domain (amino acids 601-652). It is mainly expressed in endothelial cells, platelets, stem cells, and bone marrow cells (granulocytes and monocytes).
Early research considered CD93 as an immune molecule involved in immune cell adhesion and transmigration, associated with various inflammatory and immune-related diseases (including asthma). CD93's unique positive ligand IGFBP7 (insulin-like growth factor binding protein 7) is induced in tumor blood vessels under hypoxia and VEGF stimulation. IGF1R is the receptor for IGFBP7, and the binding of IGFBP7 to CD93 disrupts the interaction between IGF1 and IGF1R, inhibiting the expansion and invasion of cancer stem cell-like cells. Blocking the interaction between IGFBP7 and CD93 can promote vascular maturation and suppress tumor growth.
