The insulin-like growth factor II (IGFII) growth control pathway is comprised of three major components: IGFII ligand, insulin-like growth factor I receptor (IGFIR), and insulin-like growth factor II receptor (IGFIIR). IGFIR andIGFIIRwork together to maintain constant circulating levels of IGFII. IGFII is a potent mitogen, produced by epithelial cells, which stimulates cell growth and prevents apoptosis by binding to IGFIR (1 ,2 ). IGFIR is a member of the receptor tyrosine kinase family (3 ) Upon binding IGFII, IGFIR autophosphorylates tyrosine residues, thereby initiating signalingFig. 1) (3 ). Both mitogenic and anti-apoptotic signaling pathways are initiated by the binding of IGFII to IGFIR (3 ).
