alpha-fetoprotein(AFP), a major plasma protein produced by the yolk sac and the liver during fetal life. Alpha-fetoprotein expression in adults is often associated with hepatoma or teratoma. The protein is thought to be the fetal counterpart of serum albumin, and the alpha-fetoprotein and albumin genes are present in tandem in the same transcriptional orientation on chromosome 4. While AFP expression in adult cells is low, it is aberrantly expressed in adult liver cancer cells. The tumor suppressor gene p53 and β-catenin are both involved in the regulation of AFP expression. In normal adult cells, p53 binds to the repressor region of the AFP gene, thereby blocking transcription. Mutations in both p53 and β-catenin are associated with aberrant expression of AFP. Research studies have shown that elevated serum AFP levels are predictive of hepatocellular carcinoma.
