Demonstration that a human hepatoma cell line produces a specific insulin-like growth factor carrier protein.
Insulin-like growth factors (IGF's) circulate in blood complexed to specific carrier proteins. The BRL 3A and BRL 3A2 rat liver cell lines secrete a 30,000-50,000 mol wt IGF carrier protein. Since the liver parenchymal cell is a likely source of IGF carrier protein synthesis, we have evaluated medium conditioned by three human hepatocellular carcinoma- or hepatoblastoma-derived cell lines for the presence of IGF carrier protein. The HEP G2 and the HEP 3B, but not the PLC/PRF/5, cell lines secrete a specific IGF carrier protein(s) into serum-free medium. This carrier protein is specific for IGF molecules. Multiplication-stimulating activity, IGF I, and IGF II were equipotent in competing for the binding of [125I]multiplication-stimulating activity to HEP G2 medium. The HEP G2 IGF carrier protein is trypsin sensitive, acid stabile, and does not contain a glycoprotein moiety. It has a molecular size of 30,000-50,000, as assessed by Sephadex G-200 gel filtration. These studies suggest that the HEP G2 cell line is a useful model to study the synthesis and secretion of human IGF carrier protein.
D001667:Binding, Competitive; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002850:Chromatography, Gel; D006801:Humans; D007328:Insulin / Q000378:metabolism; D018969:Insulin-Like Growth Factor Binding Proteins; D007335:Insulin-Like Growth Factor II; D008113:Liver Neoplasms / Q000378:metabolism*; D008970:Molecular Weight; D010455:Peptides / Q000378:metabolism; D013002:Somatomedins / Q000378:metabolism
D002352:Carrier Proteins; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D010455:Peptides; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II