High-yield and high-degree purification of human alpha-fetoprotein produced by adaptation of the human hepatoma cell line Hep G2 in a serum-free medium.

The human hepatoma cell line Hep G2 secretes both albumin and alpha-fetoprotein when grown in the presence of serum. The present report describes how adaptation to growth in serum-free medium results in a progressive switch in the expression of the two proteins; i.e., alpha-fetoprotein becomes the main protein secreted while albumin production is greatly reduced. The culture supernatant obtained, being very enriched in the protein, allows the development of a purification procedure by preparative electrophoresis. By this procedure it is possible to easily obtain large amounts of alpha-fetoprotein from a constant and unlimited source. The availability of these protein preparations should improve the reproducibility and the quality of standardization in clinical immunoassays for alpha-fetoprotein and should permit a more accurate study of the structure and biological functions of the protein.