sentences:  The development of adenomatous polyps created by uncontrolled outgrowth of epithelial cells is controlled by ephrin-eph interaction.Mice with APC mutation, without ephrin-B protein lack the means to prevent the spread of ephB positive tumor cells throughout the crypt-villi junction.One unique property of the ephrin ligands is that many have the capacity to initiate a "reverse" signal that is separate and distinct from the intracellular signal activated in Eph receptor-expressing cells.