[Studies of novel bioactive substances in the spent media of cell lines using protein-free culture system].

Many human cell lines have been maintained in fetal bovine serum (FBS)-supplemented medium. These produce and secrete many substances such as transferrin, alpha 1-antitrypsin, alpha 2-macroglobulin, alkaline phosphatase, gamma-glutamyltranspeptidase, creatine kinase, carcino-embryonic antigen, alpha-fetoprotein, and cytokines including colony stimulating factors and transforming growth factors and further they may produce small amounts of unknown substances. Usually, small amounts of substances have to be concentrated as highly as possible for detection, but FBS interferes with procedures. A protein-free culture system in an ideal method for detecting small quantities of substances which originate from cell lines without interference by FBS. Our protein-free culture system can be available in every laboratory since this is not only an economical method, but also an effective method for the saving of purification procedures. Moreover, this is a most suitable method for surveying unknown substances derived from cell lines.