AFP is a protein normally produced by the fetal liver and is present in the fluid surrounding the fetus (amniotic fluid), and crosses the placenta into the mother's blood. AFP gene expression is regulated by the interactions between steroid hormone receptors and transcriptional factors in separate signal transduction pathways. AFP functions as a binding and transporting ligand and cell growth regulator. Elevated expression level of AFP has been implicated in colorectal, ovarian, pancreatic, testicular, and certain liver cancers. High levels of AFP are also seen in some diseases such as hepatitis and colitis.